1# Active Tag 2 3> **NOTE**<br/> 4> The initial APIs of this module are supported since API version 8. Newly added APIs will be marked with a superscript to indicate their earliest API version. 5 6 7## Modules to Import 8 9``` 10import connectedTag from '@ohos.connectedTag'; 11``` 12 13 14## connectedTag.init 15 16init(): boolean 17 18Initializes the active tag chip. 19 20**Required permissions**: ohos.permission.NFC_TAG 21 22**System capability**: SystemCapability.Communication.ConnectedTag 23 24- Return value 25 | **Type**| **Description**| 26 | -------- | -------- | 27 | boolean | Returns **true** if the initialization is successful; returns **false** otherwise.| 28 29 30## connectedTag.uninit 31 32uninit(): boolean 33 34Uninitializes the active tag resources. 35 36**Required permissions**: ohos.permission.NFC_TAG 37 38**System capability**: SystemCapability.Communication.ConnectedTag 39 40- Return value 41 | **Type**| **Description**| 42 | -------- | -------- | 43 | boolean | Returns **true** if the operation is successful; returns **false** otherwise.| 44 45 46## connectedTag.readNdefTag 47 48readNdefTag(): Promise<string> 49 50Reads the content of this active tag. This method uses a promise to return the result. 51 52**Required permissions**: ohos.permission.NFC_TAG 53 54**System capability**: SystemCapability.Communication.ConnectedTag 55 56- Return value 57 | **Type**| **Description**| 58 | -------- | -------- | 59 | Promise<string> | Promise used to return the content of the active tag.| 60 61- Example 62 ``` 63 import connectedTag from '@ohos.connectedTag'; 64 65 connectedTag.readNdefTag().then(result => { 66 console.log("promise recv ndef response: " + result); 67 }); 68 ``` 69 70## connectedTag.readNdefTag 71 72readNdefTag(callback: AsyncCallback<string>): void 73 74Reads the content of this active tag. This method uses an asynchronous callback to return the result. 75 76**Required permissions**: ohos.permission.NFC_TAG 77 78**System capability**: SystemCapability.Communication.ConnectedTag 79 80- Parameters 81 | **Name**| **Type**| **Mandatory**| **Description**| 82 | -------- | -------- | -------- | -------- | 83 | callback | AsyncCallback<string> | Yes| Callback invoked to return the active tag content obtained.| 84 85- Example 86 ``` 87 import connectedTag from '@ohos.connectedTag'; 88 89 connectedTag.readNdefTag(result => { 90 console.log("callback recv ndef response: " + result); 91 }); 92 ``` 93 94## connectedTag.writeNdefTag 95 96writeNdefTag(data: string): Promise<void> 97 98Writes data to this active tag. This method uses a promise to return the result. 99 100**Required permissions**: ohos.permission.NFC_TAG 101 102**System capability**: SystemCapability.Communication.ConnectedTag 103 104- Parameters 105 | **Name**| **Type**| **Mandatory**| **Description**| 106 | -------- | -------- | -------- | -------- | 107 | data | string | Yes| Data to write. The maximum length is 1024 bytes.| 108 109- Return value 110 | **Type**| **Description**| 111 | -------- | -------- | 112 | Promise<void> | Promise used to return the result. This method returns no value.| 113 114- Example 115 ``` 116 import connectedTag from '@ohos.connectedTag'; 117 118 writeNdefTag.write("010203") 119 .then((value) => { 120 // Data is written to the tag. 121 console.log(`success to write event: ${value}`); 122 }).catch((err) => { 123 // Failed to write data to the tag. 124 console.error(`failed to write event because ${err.code}`); 125 }); 126 ``` 127 128## connectedTag.writeNdefTag 129 130writeNdefTag(data: string, callback: AsyncCallback<string>): void 131 132Writes data to this active tag. This method uses an asynchronous callback to return the result. 133 134**Required permissions**: ohos.permission.NFC_TAG 135 136**System capability**: SystemCapability.Communication.ConnectedTag 137 138- Parameters 139 | **Name**| **Type**| **Mandatory**| **Description**| 140 | -------- | -------- | -------- | -------- | 141 | data | string | Yes| Data to write. The maximum length is 1024 bytes.| 142 | callback | AsyncCallback<string> | Yes| Callback invoked to return the operation result.| 143 144- Example 145 ``` 146 import connectedTag from '@ohos.connectedTag'; 147 148 connectedTag.writeNdefTag("010203", (err, value) => { 149 if (err) { 150 // Failed to write data to the tag. 151 console.error(`failed to write event because ${err.code}`); 152 return; 153 } 154 155 // Data is written to the tag. 156 console.log(`success to write event: ${value}`); 157 }); 158 ``` 159 160## connectedTag.on('notify') 161 162on(type: "notify", callback: Callback<number>): void 163 164Registers the NFC field strength state events. 165 166**Required permissions**: ohos.permission.NFC_TAG 167 168**System capability**: SystemCapability.Communication.ConnectedTag 169 170- Parameters 171 | **Name**| **Type**| **Mandatory**| **Description**| 172 | -------- | -------- | -------- | -------- | 173 | type | string | Yes| Event type. The value is **notify**.| 174 | callback | Callback<number> | Yes| Callback invoked to return the field strength state.| 175 176- Enumerates the field strength states. 177 | **Value**| **Description**| 178 | -------- | -------- | 179 | 0 | Field off. | 180 | 1 | Field on. | 181 182 183## connectedTag.off('notify') 184 185off(type: "notify", callback?: Callback<number>): void 186 187Unregisters the NFC field strength state events. 188 189**Required permissions**: ohos.permission.NFC_TAG 190 191**System capability**: SystemCapability.Communication.ConnectedTag 192 193- Parameters 194 | **Name**| **Type**| **Mandatory**| **Description**| 195 | -------- | -------- | -------- | -------- | 196 | type | string | Yes| Event type. The value is **notify**.| 197 | callback | Callback<number> | No| Callback used to return the field strength state. If this parameter is not specified, all callbacks associated with the specified event will be unregistered.| 198 199- Example 200 ``` 201 import connectedTag from '@ohos.connectedTag'; 202 203 var NFC_RF_NOTIFY = "notify"; 204 205 var recvNfcRfNotifyFunc = result => { 206 console.info("nfc rf receive state: " + result); 207 } 208 209 // Register event 210 connectedTag.on(NFC_RF_NOTIFY, recvNfcRfNotifyFunc); 211 212 // Unregister event 213 connectedTag.off(NFC_RF_NOTIFY, recvNfcRfNotifyFunc); 214 ``` 215 216## NfcRfType 217 218Enumerates the NFC states. 219 220| Name| Default Value| Description| 221| -------- | -------- | -------- | 222| NFC_RF_LEAVE | 0 | Field off. | 223| NFC_RF_ENTER | 1 | Field on. | 224
