1# @ohos.app.ability.Want (Want) 2 3Want is a carrier for information transfer between objects (application components). Want can be used as a parameter of **startAbility** to specify a startup target and information that needs to be carried during startup, for example, **bundleName** and **abilityName**, which respectively indicate the bundle name of the target ability and the ability name in the bundle. When UIAbility A needs to start UIAbility B and transfer some data to UIAbility B, it can use Want a carrier to transfer the data. 4 5> **NOTE** 6> 7> The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version. 8 9## Modules to Import 10 11```ts 12import Want from '@ohos.app.ability.Want'; 13``` 14 15## Attributes 16 17**System capability**: SystemCapability.Ability.AbilityBase 18 19| Name | Type | Mandatory| Description | 20| ----------- | -------------------- | ---- | ------------------------------------------------------------ | 21| deviceId | string | No | ID of the device running the ability. If this field is unspecified, the local device is used. | 22| bundleName | string | No | Bundle name of the ability.| 23| moduleName | string | No| Name of the module to which the ability belongs.| 24| abilityName | string | No | Name of the ability. If both **bundleName** and **abilityName** are specified in a **Want** object, the **Want** object can match a specific ability. The value of **abilityName** must be unique in an application.| 25| action | string | No | Action to take, such as viewing and sharing application details. In implicit Want, you can define this field and use it together with **uri** or **parameters** to specify the operation to be performed on the data. For details about the definition and matching rules of implicit Want, see [Matching Rules of Explicit Want and Implicit Want](../../application-models/explicit-implicit-want-mappings.md). | 26| entities | Array\<string> | No| Additional category information (such as browser and video player) of the ability. It is a supplement to the **action** field for implicit Want. and is used to filter ability types.| 27| uri | string | No| Data carried. This field is used together with **type** to specify the data type. If **uri** is specified in a Want, the Want will match the specified URI information, including **scheme**, **schemeSpecificPart**, **authority**, and **path**.| 28| type | string | No| MIME type, that is, the type of the file to open, for example, **'text/xml'** and **'image/*'**. For details about the MIME type definition, see https://www.iana.org/assignments/media-types/media-types.xhtml?utm_source=ld246.com.| 29| parameters | {[key: string]: any} | No | Want parameters in the form of custom key-value (KV) pairs. By default, the following keys are carried:<br>- **ohos.aafwk.callerPid**: PID of the caller.<br>- **ohos.aafwk.param.callerBundleName**: bundle name of the caller.<br>- **ohos.aafwk.param.callerToken**: token of the caller.<br>- **ohos.aafwk.param.callerUid**: UID in [BundleInfo](js-apis-bundleManager-bundleInfo.md#bundleinfo-1), that is, the application UID in the bundle information.<br>- **component.startup.newRules**: whether to enable the new control rule.<br>- **moduleName**: module name of the caller. No matter what this field is set to, the correct module name will be sent to the peer.<br>- **ohos.dlp.params.sandbox**: available only for DLP files.<br>- **ability.params.backToOtherMissionStack**: whether to support redirection back across mission stacks.| 30| [flags](js-apis-ability-wantConstant.md#wantconstantflags) | number | No| How the **Want** object will be handled. By default, a number is passed in.<br>For example, **wantConstant.Flags.FLAG_ABILITY_CONTINUATION** specifies whether to start the ability in cross-device migration scenarios.| 31 32**Example** 33 34- Basic usage: called in a UIAbility object, as shown in the example below. For details about how to obtain the context, see [Obtaining the Context of UIAbility](../../application-models/uiability-usage.md#obtaining-the-context-of-uiability). 35 36 ```ts 37 import common from '@ohos.app.ability.common'; 38 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 39 let want = { 40 'deviceId': '', // An empty deviceId indicates the local device. 41 'bundleName': 'com.example.myapplication', 42 'abilityName': 'FuncAbility', 43 'moduleName': 'entry' // moduleName is optional. 44 }; 45 46 context.startAbility(want, (err) => { 47 // Start an ability explicitly. The bundleName, abilityName, and moduleName parameters work together to uniquely identify an ability. 48 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 49 }); 50 ``` 51 52- Currently, the following data types are supported: string, number, Boolean, object, array, and file descriptor (FD). 53 54 * String 55 ```ts 56 import common from '@ohos.app.ability.common'; 57 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 58 let want = { 59 bundleName: 'com.example.myapplication', 60 abilityName: 'FuncAbility', 61 parameters: { 62 keyForString: 'str', 63 }, 64 }; 65 66 context.startAbility(want, (err) => { 67 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 68 }); 69 ``` 70 * Number 71 ```ts 72 import common from '@ohos.app.ability.common'; 73 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 74 let want = { 75 bundleName: 'com.example.myapplication', 76 abilityName: 'FuncAbility', 77 parameters: { 78 keyForInt: 100, 79 keyForDouble: 99.99, 80 }, 81 }; 82 83 context.startAbility(want, (err) => { 84 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 85 }); 86 ``` 87 * Boolean 88 ```ts 89 import common from '@ohos.app.ability.common'; 90 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 91 let want = { 92 bundleName: 'com.example.myapplication', 93 abilityName: 'FuncAbility', 94 parameters: { 95 keyForBool: true, 96 }, 97 }; 98 99 context.startAbility(want, (err) => { 100 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 101 }); 102 ``` 103 * Object 104 ```ts 105 import common from '@ohos.app.ability.common'; 106 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 107 let want = { 108 bundleName: 'com.example.myapplication', 109 abilityName: 'FuncAbility', 110 parameters: { 111 keyForObject: { 112 keyForObjectString: 'str', 113 keyForObjectInt: -200, 114 keyForObjectDouble: 35.5, 115 keyForObjectBool: false, 116 }, 117 }, 118 }; 119 120 context.startAbility(want, (err) => { 121 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 122 }); 123 ``` 124 * Array 125 ```ts 126 import common from '@ohos.app.ability.common'; 127 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 128 let want = { 129 bundleName: 'com.example.myapplication', 130 abilityName: 'FuncAbility', 131 parameters: { 132 keyForArrayString: ['str1', 'str2', 'str3'], 133 keyForArrayInt: [100, 200, 300, 400], 134 keyForArrayDouble: [0.1, 0.2], 135 keyForArrayObject: [{ obj1: 'aaa' }, { obj2: 100 }], 136 }, 137 }; 138 139 context.startAbility(want, (err) => { 140 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 141 }); 142 ``` 143 * FD 144 ```ts 145 import fs from '@ohos.file.fs'; 146 147 import common from '@ohos.app.ability.common'; 148 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 149 150 let fd; 151 try { 152 fd = fs.openSync('/data/storage/el2/base/haps/pic.png').fd; 153 } catch(err) { 154 console.error(`Failed to openSync. Code: ${err.code}, message: ${err.message}`); 155 } 156 let want = { 157 'deviceId': '', // An empty deviceId indicates the local device. 158 'bundleName': 'com.example.myapplication', 159 'abilityName': 'FuncAbility', 160 'moduleName': 'entry', // moduleName is optional. 161 'parameters': { 162 'keyFd': { 'type': 'FD', 'value': fd } // {'type':'FD', 'value':fd} is a fixed usage, indicating that the data is a file descriptor. 163 } 164 }; 165 166 context.startAbility(want, (err) => { 167 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 168 }); 169 ``` 170 - Usage of **parameters**: The following uses **ability.params.backToOtherMissionStack** as an example. When a ServiceExtensionAbility starts a UIAbility, redirection back across mission stacks is supported. 171 172 ```ts 173 // (1) UIAbility1 starts a ServiceExtensionAbility. 174 let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext 175 let want = { 176 bundleName: 'com.example.myapplication1', 177 abilityName: 'ServiceExtensionAbility', 178 }; 179 180 context.startAbility(want, (err) => { 181 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 182 }); 183 184 // (2) The ServiceExtensionAbility starts UIAbility2, carrying **"ability.params.backToOtherMissionStack": true** during the startup. 185 let context = ...; // ServiceExtensionContext 186 let want = { 187 bundleName: 'com.example.myapplication2', 188 abilityName: 'MainAbility', 189 parameters: { 190 "ability.params.backToOtherMissionStack": true, 191 }, 192 }; 193 194 context.startAbility(want, (err) => { 195 console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`); 196 }); 197 ``` 198 199 Note: In the preceding example, when the ServiceExtensionAbility starts UIAbility2, **"ability.params.backToOtherMissionStack": true** is carried, indicating that redirection back across mission stacks is supported. Therefore, when you press **Back** on the page of UIAbility 2, the page of UIAbility1 page is displayed. However, if **ability.params.backToOtherMissionStack** is not carried or if **"ability.params.backToOtherMissionStack": false** is carried, the page of UIAbility1 is not displayed when you press **Back** on the page of UIAbility 2. 200
