# @ohos.nfc.tag (Standard NFC Tags)

The **nfcTag** module provides APIs for managing Near-Field Communication (NFC) tags.

> **NOTE**
>
> The initial APIs of this module are supported since API version 7. Newly added APIs will be marked with a superscript to indicate their earliest API version.

## **Declaration**

Before developing applications related to tag read and write, you must declare NFC-related attributes in the attribute configuration file of the applications. For example, declare the following attributes in the **module.json5** file:
```json
{
    "module": {
        // Attributes to declare.

        "abilities": [
            {
                "skills": [
                    {
                        "actions": [
                            // Actions to declare.

                            // Add the nfc tag action.
                            "ohos.nfc.tag.action.TAG_FOUND"
                        ],
                        "uris": [
                            {
                                "type":"tag-tech/NfcA"
                            },
                            {
                                "type":"tag-tech/IsoDep"
                            }
                            // Add other technology if neccessary,
                            // such as NfcB, NfcF, NfcV, Ndef, MifareClassic, MifareUL, and NdefFormatable.
                        ]
                    }
                ]
            }
        ],
        "requestPermissions": [
            {
                "name": "ohos.permission.NFC_TAG",
                "reason": "tag",
            }
        ]
    }
}
```
> **NOTE**
>
> - The **actions** field is mandatory. It must be **ohos.nfc.tag.action.TAG_FOUND** and cannot be changed.
> - The **type** field under **uris** must start with **tag-tech/**, followed by NfcA, NfcB, NfcF, NfcV, IsoDep, Ndef, MifareClassic, MifareUL, or NdefFormatable. If there are multiple types, enter them in different lines. Incorrect settings of this field will cause a parsing failure.
> - The **name** field under **requestPermissions** is mandatory. It must be **ohos.permission.NFC_TAG** and cannot be changed.


## **Modules to Import**

```js
import tag from '@ohos.nfc.tag';
```

## **tag.TagInfo**

Before a card with tags is read or written, **[TagInfo](#taginfo)** must be obtained to determine the tag technologies supported by the card. In this way, the application can invoke the correct API to communicate with the card.
```js
import tag from '@ohos.nfc.tag';
import UIAbility from '@ohos.app.ability.UIAbility';
import AbilityConstant from '@ohos.app.ability.AbilityConstant';
import Want from '@ohos.app.ability.Want'

export default class EntryAbility extends UIAbility {
    onCreate(want : Want, launchParam: AbilityConstant.LaunchParam) {
    // Add other code here.

    // want is initialized by the NFC service and contains tagInfo.
    let tagInfo : tag.TagInfo | null = null;
    try {
      tagInfo = tag.getTagInfo(want);
    } catch (error) {
      console.error("tag.getTagInfo catched error: " + error);
    }
    if (tagInfo == null || tagInfo == undefined) {
      console.log("no TagInfo to be created, ignore it.");
      return;
    }

    // Obtain the supported technologies for this found tag.
    let isNfcATag =  false;
    let isIsoDepTag =  false;
    for (let i = 0; i < tagInfo.technology.length; i++) {
      if (tagInfo.technology[i] == tag.NFC_A) {
        isNfcATag = true;
      }

      if (tagInfo.technology[i] == tag.ISO_DEP) {
        isIsoDepTag = true;
      }
      // Also check for technology tag.NFC_B, NFC_F, NFC_V, ISO_DEP, NDEF, MIFARE_CLASSIC, MIFARE_ULTRALIGHT, and NDEF_FORMATABLE.
    }

    // Use NfcA APIs to access the found tag.
    if (isNfcATag) {
      let nfcA : tag.NfcATag | null = null;
      try {
        nfcA = tag.getNfcATag(tagInfo);
      } catch (error) {
        console.error("tag.getNfcATag catched error: " + error);
      }
      // Other code to read or write this tag.
    }

    // Use getIsoDep APIs to access the found tag.
    if (isIsoDepTag) {
      let isoDep : tag.IsoDepTag | null = null;
      try {
        isoDep = tag.getIsoDep(tagInfo);
      } catch (error) {
        console.error("tag.getIsoDep catched error: " + error);
      }
      // Other code to read or write this tag.
    }
    // Use the same code to handle "NfcA/NfcB/NfcF/NfcV/Ndef/MifareClassic/MifareUL/NdefFormatable".
  }
}
```

## tag.getNfcATag<sup>(deprecated)</sup>

getNfcATag(tagInfo: [TagInfo](#taginfo)): [NfcATag](js-apis-nfctech.md#nfcatag)

Obtains an **NfcATag** object, which allows access to the tags that use the NFC-A technology.

> **NOTE**
> This API is supported since API version 7 and deprecated since API version 9. You are advised to use [tag.getNfcA](#taggetnfca9).

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcATag](js-apis-nfctech.md#nfcatag) | **NfcATag** object obtained.|

## tag.getNfcA<sup>9+</sup>

getNfcA(tagInfo: [TagInfo](#taginfo)): [NfcATag](js-apis-nfctech.md#nfcatag)

Obtains an **NfcATag** object, which allows access to the tags that use the NFC-A technology.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcATag](js-apis-nfctech.md#nfcatag) | **NfcATag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getNfcBTag<sup>(deprecated)</sup>

getNfcBTag(tagInfo: [TagInfo](#taginfo)): [NfcBTag](js-apis-nfctech.md#nfcbtag)

Obtains an **NfcBTag** object, which allows access to the tags that use the NFC-B technology.

> **NOTE**
> This API is supported since API version 7 and deprecated since API version 9. You are advised to use [tag.getNfcB](#taggetnfcb9).

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcBTag](js-apis-nfctech.md#nfcbtag) | **NfcBTag** object obtained.|

## tag.getNfcB<sup>9+</sup>

getNfcB(tagInfo: [TagInfo](#taginfo)): [NfcBTag](js-apis-nfctech.md#nfcbtag)

Obtains an **NfcBTag** object, which allows access to the tags that use the NFC-B technology.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcBTag](js-apis-nfctech.md#nfcbtag) | **NfcBTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getNfcFTag<sup>(deprecated)</sup>

getNfcFTag(tagInfo: [TagInfo](#taginfo)): [NfcFTag](js-apis-nfctech.md#nfcftag)

Obtains an **NfcFTag** object, which allows access to the tags that use the NFC-F technology.

> **NOTE**
> This API is supported since API version 7 and deprecated since API version 9. You are advised to use [tag.getNfcF](#taggetnfcf9).

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcFTag](js-apis-nfctech.md#nfcftag) | **NfcFTag** object obtained.|

## tag.getNfcF<sup>9+</sup>

getNfcF(tagInfo: [TagInfo](#taginfo)): [NfcFTag](js-apis-nfctech.md#nfcftag)

Obtains an **NfcFTag** object, which allows access to the tags that use the NFC-F technology.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcFTag](js-apis-nfctech.md#nfcftag) | **NfcFTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getNfcVTag<sup>(deprecated)</sup>

getNfcVTag(tagInfo: [TagInfo](#taginfo)): [NfcVTag](js-apis-nfctech.md#nfcvtag)

Obtains an **NfcVTag** object, which allows access to the tags that use the NFC-V technology.

> **NOTE**
> This API is supported since API version 7 and deprecated since API version 9. You are advised to use [tag.getNfcV](#taggetnfcv9).

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcVTag](js-apis-nfctech.md#nfcvtag) | **NfcVTag** object obtained.|

## tag.getNfcV<sup>9+</sup>

getNfcV(tagInfo: [TagInfo](#taginfo)): [NfcVTag](js-apis-nfctech.md#nfcvtag)

Obtains an **NfcVTag** object, which allows access to the tags that use the NFC-V technology.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                             | **Description**          |
| ------------------------------------- | ------------------ |
| [NfcVTag](js-apis-nfctech.md#nfcvtag) | **NfcVTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getIsoDep<sup>9+</sup>

getIsoDep(tagInfo: [TagInfo](#taginfo)): [IsoDepTag](js-apis-nfctech.md#isoDepTag9 )

Obtains an **IsoDepTag** object, which allows access to the tags that use the ISO-DEP technology.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                                  | **Description**                                               |
| ------------------------------------------ | ------------------------------------------------------- |
| [IsoDepTag](js-apis-nfctech.md#isodeptag9) | **IsoDepTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getNdef<sup>9+</sup>

getNdef(tagInfo: [TagInfo](#taginfo)): [NdefTag](js-apis-nfctech.md#ndeftag9)

Obtains an **NdefTag** object, which allows access to the tags in the NFC Data Exchange Format (NDEF).

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                              | **Description**                                           |
| -------------------------------------- | --------------------------------------------------- |
| [NdefTag](js-apis-nfctech.md#ndeftag9) | **NdefTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getMifareClassic<sup>9+</sup>

getMifareClassic(tagInfo: [TagInfo](#taginfo)): [MifareClassicTag](js-apis-nfctech.md#mifareclassictag9)

Obtains a **MifareClassicTag** object, which allows access to the tags that use MIFARE Classic.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                                                 | **Description**                                                               |
| --------------------------------------------------------- | ----------------------------------------------------------------------- |
| [MifareClassicTag](js-apis-nfctech.md#mifareclassictag-9) | **MifareClassicTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getMifareUltralight<sup>9+</sup>

getMifareUltralight(tagInfo: [TagInfo](#taginfo)): [MifareUltralightTag](js-apis-nfctech.md#mifareultralighttag9)

Obtains a **MifareUltralightTag** object, which allows access to the tags that use MIFARE Ultralight.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**
| Name | Type               | Mandatory| Description                                                         |
| ------- | ------------------- | ---- | ------------------------------------------------------------- |
| tagInfo | [TagInfo](#taginfo) | Yes  | Tag information including the technology type and related parameters, which are obtained from **tag.getTagInfo(want: Want)**.|

**Return value**

| **Type**                                                      | **Description**                                                                     |
| -------------------------------------------------------------- | ----------------------------------------------------------------------------- |
| [MifareUltralightTag](js-apis-nfctech.md#mifareultralighttag9) | **MifareUltralightTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getNdefFormatable<sup>9+</sup>

getNdefFormatable(tagInfo: [TagInfo](#taginfo)): [NdefFormatableTag](js-apis-nfctech.md#ndefformatabletag9)

Obtains an **NdefFormatableTag** object, which allows access to the tags that are NDEF formattable.

**System capability**: SystemCapability.Communication.NFC.Tag

**Return value**

| **Type**                                                 | **Description**                                                                 |
| --------------------------------------------------------- | ------------------------------------------------------------------------- |
| [NdefFormatableTag](js-apis-nfctech.md#ndefformatabletag) | **NdefFormatableTag** object obtained.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100201  | Tag running state is abnormal in service. |

## tag.getTagInfo<sup>9+</sup>

getTagInfo(want: [Want](js-apis-app-ability-want.md#Want)): [TagInfo](#taginfo)

Obtains **TagInfo** from **Want**, which is initialized by the NFC service and contains the attributes required by **TagInfo**.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name| Type                                    | Mandatory| Description                                               |
| ------ | ---------------------------------------- | ---- | --------------------------------------------------- |
| want   | [Want](js-apis-app-ability-want.md#Want) | Yes  | Data obtained from the parameters of the **onCreate** entry function when an ability is dispatched.|

**Return value**

| **Type**           | **Description**                                    |
| ------------------- | -------------------------------------------- |
| [TagInfo](#taginfo) | **TagInfo** object obtained.|

## tag.registerForegroundDispatch<sup>10+</sup>

registerForegroundDispatch(elementName: [ElementName](js-apis-bundleManager-elementName.md), discTech: number[], callback: AsyncCallback&lt;[TagInfo](#taginfo)&gt;): void

Registers listening for the card reading events of an NFC tag foreground application. You can set the supported tag technologies in **discTech**, and obtain the [TagInfo](#taginfo) read in a callback. <br>This API must be used with [tag.unregisterForegroundDispatch](#tagunregisterforegrounddispatch10) in pairs. The registered event listening must be unregistered before the page exits the foreground or the page is destroyed.

**Required permissions**: ohos.permission.NFC_TAG

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name      | Type    | Mandatory| Description                                                   |
| ------------ | -------- | ---- | ------------------------------------------------------- |
| elementName   |  [ElementName](js-apis-bundleManager-elementName.md)   | Yes  | Information about the application page, which must contain at least the bundle name and ability name.         |
| discTech         |  number[]   | Yes  | Technologies supported by the foreground dispatch system. Each number indicates the constant value of the supported technology. Based on the value of **number**, the system sets tag technologies ([NFC_A](#technology-type-definition), [NFC_B](#technology-type-definition), and [NFC_F](#technology-type-definition), and [NFC_V](#technology-type-definition)) for NFC card read polling and disable card emulation. If the **number** length is 0, both card read polling and card emulation will be disabled.|
| callback | AsyncCallback&lt;[TagInfo](#taginfo)&gt; | Yes  | Callback invoked to return the card read event in the foreground.|

**Example**

See the example of [tag.unregisterForegroundDispatch](#tagunregisterforegrounddispatch10).

## tag.unregisterForegroundDispatch<sup>10+</sup>

unregisterForegroundDispatch(elementName: [ElementName](js-apis-bundleManager-elementName.md)): void

Unregisters the listening for card reading events of an NFC tag foreground application. The registered event listening must be unregistered before the page exits the foreground or the page is destroyed.

**Required permissions**: ohos.permission.NFC_TAG

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name      | Type    | Mandatory| Description                                                   |
| ------------ | -------- | ---- | ------------------------------------------------------- |
| elementName   |  [ElementName](js-apis-bundleManager-elementName.md)   | Yes  | Information about the application page, which must contain at least the bundle name and ability name.         |

**Example**

```js
import Want from '@ohos.app.ability.Want';
import UIAbility from '@ohos.app.ability.UIAbility';
import tag from '@ohos.nfc.tag';
import { BusinessError } from '@ohos.base';
import bundleManager from '@ohos.bundle.bundleManager';
import AbilityConstant from '@ohos.app.ability.AbilityConstant';

let discTech : number[] = [tag.NFC_A, tag.NFC_B]; // replace with the tech(s) that is needed by foreground ability
let elementName : bundleManager.ElementName;
function foregroundCb(err : BusinessError, tagInfo : tag.TagInfo) {
    if (err as BusinessError) {
        if (!err) {
            console.log("foreground callback: tag found tagInfo = ", JSON.stringify(tagInfo));
        } else {
            console.log("foreground callback err: " + (err as BusinessError).message);
            return;
        }
    }
  // Other operations of taginfo.
}

export default class MainAbility extends UIAbility {
    OnCreate(want : Want, launchParam : AbilityConstant.LaunchParam) {
        console.log("OnCreate");
        elementName = {
            bundleName: want.bundleName as string,
            abilityName: want.abilityName as string,
            moduleName: want.moduleName as string
        }
    }

    onForeground() {
        console.log("onForeground");
        try {
            tag.registerForegroundDispatch(elementName, discTech, foregroundCb);
        } catch (e) {
            console.error("registerForegroundDispatch error: " + (e as BusinessError).message);
        }
    }

    onBackground() {
        console.log("onBackground");
        try {
            tag.unregisterForegroundDispatch(elementName);
        } catch (e) {
            console.error("registerForegroundDispatch error: " + (e as BusinessError).message);
        }
    }

    onWindowStageDestroy() {
        console.log("onWindowStageDestroy");
        try {
            tag.unregisterForegroundDispatch(elementName);
        } catch (e) {
            console.error("registerForegroundDispatch error: " + (e as BusinessError).message);
        }
    }

  // Override other lifecycle functions.
}
```

## tag.on<sup>11+</sup>

on(type: 'readerMode', elementName: [ElementName](js-apis-bundleManager-elementName.md), discTech: number[], callback: AsyncCallback&lt;[TagInfo](#taginfo)&gt;): void

Sets the NFC card reader mode and subscribes to card reading events when the application page is in the foreground. The **discTech** parameter specifies the supported tag technology types, and the callback returns the [TagInfo](#taginfo) obtained. This API must be used with [tag.off](#tagoff11) in pairs. If the NFC card reader mode is set by [tag.on](#tagon11), you must use call **tag.off** to exit the mode when the application page exits the foreground or the page is destroyed.

**Required permissions**: ohos.permission.NFC_TAG

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name      | Type    | Mandatory| Description                                                   |
| ------------ | -------- | ---- | ------------------------------------------------------- |
| type    | string  | Yes  | Type of the callback to register.|
| elementName   |  [ElementName](js-apis-bundleManager-elementName.md)   | Yes  | Element name of the application, which must contain at least the bundle name and ability name.         |
| discTech         |  number[]   | Yes  | Technologies supported by the card reader mode. Each number indicates the constant value of the supported technology. Based on the value of **number**, the system sets tag technologies ([NFC_A](#technology-type-definition), [NFC_B](#technology-type-definition), and [NFC_F](#technology-type-definition), and [NFC_V](#technology-type-definition)) for NFC card read polling and disable card emulation. If the **number** length is 0, both card read polling and card emulation will be disabled.|
| callback | AsyncCallback&lt;[TagInfo](#taginfo)&gt; | Yes  | Callback used to listen for the card reader mode, which returns the tag information read.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100202  | Invalid element status.|

**Example**

See the example of [tag.off](#tagoff11).

## tag.off<sup>11+</sup>

off(type: 'readerMode', elementName: [ElementName](js-apis-bundleManager-elementName.md), callback?: AsyncCallback&lt;[TagInfo](#taginfo)&gt;): void

Exits the NFC card reader mode and unsubscribes from the card reading events. If the NFC card reader mode is set by [tag.on](#tagon11), you must use this API to exit the mode when the application page exits the foreground or the page is destroyed.

**Required permissions**: ohos.permission.NFC_TAG

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name      | Type    | Mandatory| Description                                                   |
| ------------ | -------- | ---- | ------------------------------------------------------- |
| type    | string  | Yes  | Type of the callback to unregister.|
| elementName   |  [ElementName](js-apis-bundleManager-elementName.md)   | Yes  | Element name of the application, which must contain at least the bundle name and ability name.         |
| callback | AsyncCallback&lt;[TagInfo](#taginfo)&gt; | No  | Callback for listening for the card reading in the foreground.|

**Error codes**

For details about the error codes, see [NFC Error Codes](../errorcodes/errorcode-nfc.md).

| ID| Error Message                                 |
| -------- | ----------------------------------------- |
| 3100203  | off() must be used with on() in pairs.|

**Example**

```js
import Want from '@ohos.app.ability.Want';
import UIAbility from '@ohos.app.ability.UIAbility';
import tag from '@ohos.nfc.tag';
import { BusinessError } from '@ohos.base';
import bundleManager from '@ohos.bundle.bundleManager';
import AbilityConstant from '@ohos.app.ability.AbilityConstant';

let discTech : number[] = [tag.NFC_A, tag.NFC_B]; // replace with the tech(s) that is needed by foreground ability
let elementName : bundleManager.ElementName;

function readerModeCb(err : BusinessError, tagInfo : tag.TagInfo) {
    if (err as BusinessError) {
        if (!err) {
            console.log("offCallback: tag found tagInfo = ", JSON.stringify(tagInfo));
        } else {
            console.error("offCallback err: " + (err as BusinessError).message);
            return;
        }
    }
  // other Operations of taginfo
}

export default class MainAbility extends UIAbility {
    OnCreate(want : Want, launchParam : AbilityConstant.LaunchParam) {
        console.log("OnCreate");
        elementName = {
            bundleName: want.bundleName as string,
            abilityName: want.abilityName as string,
            moduleName: want.moduleName as string
        }
    }

    onForeground() {
        console.log("on start");
        try {
            tag.on('readerMode', elementName, discTech, readerModeCb);
        } catch (e) {
            console.error("tag.on error: " + (e as BusinessError).message);
        }
    }

    onBackground() {
        console.log("onBackground");
        try {
            tag.off('readerMode', elementName, readerModeCb);
        } catch (e) {
            console.error("tag.off error: " + (e as BusinessError).message);
        }
    }

    onWindowStageDestroy() {
        console.log("onWindowStageDestroy");
        try {
            tag.off('readerMode', elementName, readerModeCb);
        } catch (e) {
            console.error("tag.off error: " + (e as BusinessError).message);
        }
    }

  // override other lifecycle functions
}
```

## tag.ndef.makeUriRecord<sup>9+</sup>

makeUriRecord(uri: string): [NdefRecord](#ndefrecord9)

Creates an NDEF record based on the specified URI.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name| Type  | Mandatory| Description                             |
| ------ | ------ | ---- | --------------------------------- |
| uri    | string | Yes  | Data to write to the NDEF record.|

**Return value**

| **Type**                  | **Description**                                                    |
| -------------------------- | ------------------------------------------------------------ |
| [NdefRecord](#ndefrecord9) | NDEF record created. For details, see *NFCForum-TS-NDEF_1.0*.|

**Example**

```js
import tag from '@ohos.nfc.tag';

try {
    let uri = "https://gitee.com/openharmony"; // change it to be correct.
    let ndefRecord = tag.ndef.makeUriRecord(uri);
    if (ndefRecord != undefined) {
        console.log("ndefMessage makeUriRecord rtdType: " + ndefRecord.rtdType);
        console.log("ndefMessage makeUriRecord payload: " + ndefRecord.payload);
    } else {
        console.log("ndefMessage makeUriRecord ndefRecord: " + ndefRecord);
    }
} catch (busiError) {
    console.error("ndefMessage makeUriRecord catched busiError: " + busiError);
}
```

## tag.ndef.makeTextRecord<sup>9+</sup>

makeTextRecord(text: string, locale: string): [NdefRecord](#ndefrecord9)

Creates an NDEF record based on the specified text data and encoding type.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name| Type  | Mandatory| Description                                 |
| ------ | ------ | ---- | ------------------------------------- |
| text   | string | Yes  | Text to write to the NDEF record.|
| locale | string | Yes  | Encoding mode of the text.             |

**Return value**

| **Type**                  | **Description**                                                    |
| -------------------------- | ------------------------------------------------------------ |
| [NdefRecord](#ndefrecord9) | NDEF record created. For details, see *NFCForum-TS-NDEF_1.0*.|

**Example**

```js
import tag from '@ohos.nfc.tag';

try {
    let text = "Hello World";   // change it to be correct.
    let locale = "en"; // change it to be correct.
    let ndefRecord = tag.ndef.makeTextRecord(text, locale);
    if (ndefRecord != undefined) {
        console.log("ndefMessage makeTextRecord rtdType: " + ndefRecord.rtdType);
        console.log("ndefMessage makeTextRecord payload: " + ndefRecord.payload);
    } else {
        console.log("ndefMessage makeTextRecord ndefRecord: " + ndefRecord);
    }
} catch (busiError) {
    console.error("ndefMessage makeTextRecord catched busiError: " + busiError);
}
```


## tag.ndef.makeMimeRecord<sup>9+</sup>

makeMimeRecord(mimeType: string, mimeData: number[]): [NdefRecord](#ndefrecord9)

Creates an NDEF record based on the specified MIME data and type.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name  | Type    | Mandatory| Description                                                   |
| -------- | -------- | ---- | ------------------------------------------------------- |
| mimeType | string   | Yes  | MIME type that complies with RFC rules, for example, **text/plain** or **image/jpeg**.|
| mimeData | number[] | Yes  | MIME data, which consists of hexadecimal numbers ranging from **0x00** to **0xFF**.|

**Return value**

| **Type**                  | **Description**                                                    |
| -------------------------- | ------------------------------------------------------------ |
| [NdefRecord](#ndefrecord9) | NDEF record created. For details, see *NFCForum-TS-NDEF_1.0*.|

**Example**

```js
import tag from '@ohos.nfc.tag';

try {
    let mimeType = "text/plain";   // change it to be correct.
    let mimeData = [0x01, 0x02, 0x03, 0x04]; // change it to be correct.
    let ndefRecord = tag.ndef.makeMimeRecord(mimeType, mimeData);
    if (ndefRecord != undefined) {
        console.log("ndefMessage makeMimeRecord rtdType: " + ndefRecord.rtdType);
        console.log("ndefMessage makeMimeRecord payload: " + ndefRecord.payload);
    } else {
        console.log("ndefMessage makeMimeRecord ndefRecord: " + ndefRecord);
    }
} catch (busiError) {
    console.error("ndefMessage makeMimeRecord catched busiError: " + busiError);
}
```
## tag.ndef.makeExternalRecord<sup>9+</sup>

makeExternalRecord(domainName: string, type: string, externalData: number[]): [NdefRecord](#ndefrecord9)

Creates an NDEF record based on application-specific data.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name      | Type    | Mandatory| Description                                                   |
| ------------ | -------- | ---- | ------------------------------------------------------- |
| domainName   | string   | Yes  | Bundle name of the application or domain name of the organization that releases the applications.         |
| type         | string   | Yes  | Type of the application data.                                   |
| externalData | number[] | Yes  | Application data, which consists of hexadecimal numbers ranging from **0x00** to **0xFF**.|

**Return value**

| **Type**                  | **Description**                                                    |
| -------------------------- | ------------------------------------------------------------ |
| [NdefRecord](#ndefrecord9) | NDEF record created. For details, see *NFCForum-TS-NDEF_1.0*.|

**Example**

```js
import tag from '@ohos.nfc.tag';

try {
    let domainName = "ohos.nfc.application"; // change it to be correct.
    let type = "test"; // change it to be correct.
    let externalData = [0x01, 0x02, 0x03, 0x04]; // change it to be correct.
    let ndefRecord = tag.ndef.makeExternalRecord(domainName, type, externalData);
    if (ndefRecord != undefined) {
        console.log("ndefMessage makeExternalRecord rtdType: " + ndefRecord.rtdType);
        console.log("ndefMessage makeExternalRecord payload: " + ndefRecord.payload);
    } else {
        console.log("ndefMessage makeExternalRecord ndefRecord: " + ndefRecord);
    }
} catch (busiError) {
    console.error("ndefMessage makeExternalRecord catched busiError: " + busiError);
}
```

## tag.ndef.messageToBytes<sup>9+</sup>

messageToBytes(ndefMessage: [NdefMessage](js-apis-nfctech.md#ndefmessage9)): number[]

Converts an NDEF message to bytes.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| Name     | Type                                          | Mandatory| Description              |
| ----------- | ---------------------------------------------- | ---- | ------------------ |
| ndefMessage | [NdefMessage](js-apis-nfctech.md#ndefmessage9) | Yes  | NDEF message to convert.|

**Return value**

| **Type**| **Description**                                                                             |
| -------- | ------------------------------------------------------------------------------------- |
| number[] | NDEF message in bytes, which consists of hexadecimal numbers ranging from **0x00** to **0xFF**.|

**Example**

```js
import tag from '@ohos.nfc.tag';

let rawData = [0xD1, 0x01, 0x03, 0x54, 0x4E, 0x46, 0x43]; // MUST can be parsed as NDEF Record.
try {
    let ndefMessage = tag.ndef.createNdefMessage(rawData);
    console.log("ndef createNdefMessage, ndefMessage: " + ndefMessage);
    let rawData2 = tag.ndef.messageToBytes(ndefMessage);
    console.log("ndefMessage messageToBytes rawData2: " + rawData2);
} catch (busiError) {
    console.error("ndef createNdefMessage busiError: " + busiError);
}
```
## tag.ndef.createNdefMessage<sup>9+</sup>

createNdefMessage(data: number[]): [NdefMessage](js-apis-nfctech.md#ndefmessage9)

Creates an NDEF message from raw byte data. The data must comply with the NDEF record format. Otherwise, the NDE record list contained in the **NdefMessage** object will be empty.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| **Name**| **Type**| **Mandatory**| **Description**                                                                          |
| ---------- | -------- | -------- | ---------------------------------------------------------------------------------- |
| data       | number[] | Yes      | Raw byte data, which consists of hexadecimal numbers ranging from **0x00** to **0xFF**. The data must comply with the NDEF record format.|

**Return value**

| **Type**                                      | **Description**                                                     |
| ---------------------------------------------- | ------------------------------------------------------------- |
| [NdefMessage](js-apis-nfctech.md#ndefmessage9) | NDEF message created. For details, see *NFCForum-TS-NDEF_1.0*.|

**Example**
```js
import tag from '@ohos.nfc.tag';

let rawData = [0xD1, 0x01, 0x03, 0x54, 0x4E, 0x46, 0x43];  // MUST can be parsed as NDEF Record.
try {
    let ndefMessage = tag.ndef.createNdefMessage(rawData);
    console.log("ndef createNdefMessage, ndefMessage: " + ndefMessage);
} catch (busiError) {
    console.error("ndef createNdefMessage busiError: " + busiError);
}
```

## tag.ndef.createNdefMessage<sup>9+</sup>

createNdefMessage(ndefRecords: NdefRecord[]): [NdefMessage](js-apis-nfctech.md#ndefmessage9)

Creates an NDEF message from the NDEF records list.

**System capability**: SystemCapability.Communication.NFC.Tag

**Parameters**

| **Name** | **Type**                                     | **Mandatory**| **Description**                                                        |
| ----------- | --------------------------------------------- | -------- | ---------------------------------------------------------------- |
| ndefRecords | [NdefRecord](js-apis-nfcTag.md#ndefrecord9)[] | Yes      | NDEF record list used to create the NDEF message. For details, see *NFCForum-TS-NDEF_1.0*.|

**Return value**

| **Type**                                      | **Description**                                                     |
| ---------------------------------------------- | ------------------------------------------------------------- |
| [NdefMessage](js-apis-nfctech.md#ndefmessage9) | NDEF message created. For details, see *NFCForum-TS-NDEF_1.0*.|

**Example**

```js
import tag from '@ohos.nfc.tag';

let uriRecord = tag.ndef.makeUriRecord("https://gitee.com/openharmony");
let textRecord = tag.ndef.makeTextRecord("Hello World", "en");
let ndefRecords = [uriRecord, textRecord];
try {
    let ndefMessage = tag.ndef.createNdefMessage(ndefRecords);
    console.log("ndef createNdefMessage ndefMessage: " + ndefMessage);
} catch (busiError) {
    console.error("ndef createNdefMessage busiError: " + busiError);
}
```

## TagInfo

Defines the **TagInfo** object, which provides information about the tag technologies supported by a card.

**System capability**: SystemCapability.Communication.NFC.Tag

**Required permissions**: ohos.permission.NFC_TAG

| **Name**                     | **Type**                                                     | **Readable**| **Writable**| **Description**                                                                                    |
| ----------------------------- | ------------------------------------------------------------- | -------- | -------- | -------------------------------------------------------------------------------------------- |
| uid<sup>9+</sup>              | number[]                                                      | Yes      | No      | Tag unique identifier (UID), which consists of hexadecimal numbers ranging from **0x00** to **0xFF**.                                    |
| technology<sup>9+</sup>       | number[]                                                      | Yes      | No      | Supported tag technologies. Each number is a constant indicating the supported technology.                                    |
| supportedProfiles             | number[]                                                      | Yes      | No      | Supported profiles. This parameter is not supported since API version 9. Use [tag.TagInfo#technology](#taginfo) instead.           |
| extrasData<sup>9+</sup>       | [PacMap](js-apis-inner-ability-dataAbilityHelper.md#pacmap)[] | Yes      | No      | Extended attribute value of the tag technology.<br>**System API**: This is a system API.                           |
| tagRfDiscId<sup>9+</sup>      | number                                                        | Yes      | No      | ID allocated when the tag is discovered.<br>**System API**: This is a system API.                                 |
| remoteTagService<sup>9+</sup> | [rpc.RemoteObject](js-apis-rpc.md#remoteobject)               | Yes      | No      | Remote object of the NFC service process used for interface communication between the client and the service.<br>**System API**: This is a system API.|
## NdefRecord<sup>9+</sup>
Defines an NDEF record. For details, see *NFCForum-TS-NDEF_1.0*.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**| **Type**| **Readable**| **Writable**| **Description**                                                                                 |
| -------- | -------- | -------- | -------- | ----------------------------------------------------------------------------------------- |
| tnf      | number   | Yes      | No      | Type name field (TNF) of the NDEF record.                                                      |
| rtdType  | number[] | Yes      | No      | Record type definition (RTD) of the NDEF record. It consists of hexadecimal numbers ranging from **0x00** to **0xFF**.|
| id       | number[] | Yes      | No      | NDEF record ID, which consists of hexadecimal numbers ranging from **0x00** to **0xFF**.                               |
| payload  | number[] | Yes      | No      | NDEF payload, which consists of hexadecimal numbers ranging from **0x00** to **0xFF**.                          |

## Technology Type Definition
Enumerates the tag technology types.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**                    | **Value**| **Description**                   |
| ---------------------------- | ------ | --------------------------- |
| NFC_A                        | 1      | NFC-A (ISO 14443-3A). |
| NFC_B                        | 2      | NFC-B (ISO 14443-3B). |
| ISO_DEP                      | 3      | ISO-DEP (ISO 14443-4).|
| NFC_F                        | 4      | NFC-F (JIS 6319-4).   |
| NFC_V                        | 5      | NFC-V (ISO 15693).    |
| NDEF                         | 6      | NDEF.                 |
| NDEF_FORMATABLE<sup>9+</sup> | 7      | NDEF formattable.     |
| MIFARE_CLASSIC               | 8      | MIFARE Classic.       |
| MIFARE_ULTRALIGHT            | 9      | MIFARE Ultralight.     |

## TnfType<sup>9+</sup>
Enumerates the TNF types. For details, see *NFCForum-TS-NDEF_1.0*.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**        | **Value**| **Description**                                        |
| ---------------- | ------ | ------------------------------------------------ |
| TNF_EMPTY        | 0x0    | Empty.                                         |
| TNF_WELL_KNOWN   | 0x1    | NFC Forum Well Known Type [NFC RTD].           |
| TNF_MEDIA        | 0x2    | Media-type as defined in RFC 2046 [RFC 2046].  |
| TNF_ABSOLUTE_URI | 0x3    | Absolute URI as defined in RFC 3986 [RFC 3986].|
| TNF_EXT_APP      | 0x4    | NFC Forum external type [NFC RTD].             |
| TNF_UNKNOWN      | 0x5    | Unknown.                                       |
| TNF_UNCHANGED    | 0x6    | Unchanged (see section 2.3.3 in *NFCForum-TS-NDEF_1.0*).                 |

## NDEF Record RTD
Enumerates the NDEF record types. For details about the RTD, see *NFCForum-TS-NDEF_1.0*.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**             | **Value**| **Description**               |
| --------------------- | ------ | ----------------------- |
| RTD_TEXT<sup>9+</sup> | [0x54] | NDEF record of the text type.|
| RTD_URI<sup>9+</sup>  | [0x55] | NDEF record of the URI type. |

## NfcForumType<sup>9+</sup>
Enumerates the NFC Forum tag types.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**        | **Value**| **Description**            |
| ---------------- | ------ | -------------------- |
| NFC_FORUM_TYPE_1 | 1      | NFC Forum tag type 1.      |
| NFC_FORUM_TYPE_2 | 2      | NFC Forum tag type 2.      |
| NFC_FORUM_TYPE_3 | 3      | NFC Forum tag type 3.      |
| NFC_FORUM_TYPE_4 | 4      | NFC Forum tag type 4.      |
| MIFARE_CLASSIC   | 101    | MIFARE Classic.|

## MifareClassicType<sup>9+</sup>
Enumerates the MIFARE Classic tag types.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**    | **Value**| **Description**            |
| ------------ | ------ | -------------------- |
| TYPE_UNKNOWN | 0      | Unknown type.  |
| TYPE_CLASSIC | 1      | MIFARE Classic.|
| TYPE_PLUS    | 2      | MIFARE Plus.   |
| TYPE_PRO     | 3      | MIFARE Pro.    |

## MifareClassicSize<sup>9+</sup>
Enumerates the sizes of a MIFARE Classic tag.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**    | **Value**| **Description**                         |
| ------------ | ------ | --------------------------------- |
| MC_SIZE_MINI | 320    | Each tag has 5 sectors, and each sector has 4 blocks. |
| MC_SIZE_1K   | 1024   | Each tag has 16 sectors, and each sector has 4 blocks.|
| MC_SIZE_2K   | 2048   | Each tag has 32 sectors, and each sector has 4 blocks.|
| MC_SIZE_4K   | 4096   | Each tag has 40 sectors, and each sector has 4 blocks.|

## MifareUltralightType<sup>9+</sup>
Enumerates the MIFARE Ultralight tag types.

**System capability**: SystemCapability.Communication.NFC.Tag

| **Name**         | **Value**| **Description**                 |
| ----------------- | ------ | ------------------------- |
| TYPE_UNKNOWN      | 0      | Unknown type.     |
| TYPE_ULTRALIGHT   | 1      | MIFARE Ultralight.  |
| TYPE_ULTRALIGHT_C | 2      | MIFARE Ultralight C.|

 <!--no_check-->