harmony 鸿蒙@ohos.app.ability.Want (Want)

2022-12-13
浏览 (472)

@ohos.app.ability.Want (Want)

Want 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.

NOTE

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.

Modules to Import

import Want from '@ohos.app.ability.Want';

Attributes

System capability: SystemCapability.Ability.AbilityBase

Name	Type	Mandatory	Description
deviceId	string	No	ID of the device running the ability. If this field is unspecified, the local device is used.
bundleName	string	No	Bundle name of the ability.
moduleName	string	No	Name of the module to which the ability belongs.
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.
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.
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.
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.
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.
parameters	{[key: string]: any}	No	Want parameters in the form of custom key-value (KV) pairs. By default, the following keys are carried: - ohos.aafwk.callerPid: PID of the caller. - ohos.aafwk.param.callerBundleName: bundle name of the caller. - ohos.aafwk.param.callerToken: token of the caller. - ohos.aafwk.param.callerUid: UID in BundleInfo, that is, the application UID in the bundle information. - component.startup.newRules: whether to enable the new control rule. - moduleName: module name of the caller. No matter what this field is set to, the correct module name will be sent to the peer. - ohos.dlp.params.sandbox: available only for DLP files. - ability.params.backToOtherMissionStack: whether to support redirection back across mission stacks.
flags	number	No	How the Want object will be handled. By default, a number is passed in. For example, wantConstant.Flags.FLAG_ABILITY_CONTINUATION specifies whether to start the ability in cross-device migration scenarios.

Example

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.

  import common from '@ohos.app.ability.common';
  import Want from '@ohos.app.ability.Want';

  let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext
  let want: Want = {
    deviceId: '', // An empty deviceId indicates the local device.
    bundleName: 'com.example.myapplication',
    abilityName: 'FuncAbility',
    moduleName: 'entry', // moduleName is optional.
  };
  
  context.startAbility(want, (err) => {
    // Start an ability explicitly. The bundleName, abilityName, and moduleName parameters work together to uniquely identify an ability.
    console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
  });

Currently, the following data types are supported: string, number, Boolean, object, array, and file descriptor (FD).

String

import common from '@ohos.app.ability.common';
import Want from '@ohos.app.ability.Want';


let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext
let want: Want = {
  bundleName: 'com.example.myapplication',
  abilityName: 'FuncAbility',
  parameters: {
    keyForString: 'str',
  },
};


context.startAbility(want, (err) => {
  console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
});

Number

import common from '@ohos.app.ability.common';
import Want from '@ohos.app.ability.Want';


let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext
let want: Want = {
  bundleName: 'com.example.myapplication',
  abilityName: 'FuncAbility',
  parameters: {
    keyForInt: 100,
    keyForDouble: 99.99,
  },
};


context.startAbility(want, (err) => {
  console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
});

Boolean

import common from '@ohos.app.ability.common';
import Want from '@ohos.app.ability.Want';


let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext
let want: Want = {
  bundleName: 'com.example.myapplication',
  abilityName: 'FuncAbility',
  parameters: {
    keyForBool: true,
  },
};


context.startAbility(want, (err) => {
  console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
});

Object

import common from '@ohos.app.ability.common';
import Want from '@ohos.app.ability.Want';


let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext
let want: Want = {
  bundleName: 'com.example.myapplication',
  abilityName: 'FuncAbility',
  parameters: {
    keyForObject: {
      keyForObjectString: 'str',
      keyForObjectInt: -200,
      keyForObjectDouble: 35.5,
      keyForObjectBool: false,
    },
  },
};


context.startAbility(want, (err) => {
  console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
});

Array

import common from '@ohos.app.ability.common';
import Want from '@ohos.app.ability.Want';


let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext
let want: Want = {
  bundleName: 'com.example.myapplication',
  abilityName: 'FuncAbility',
  parameters: {
    keyForArrayString: ['str1', 'str2', 'str3'],
    keyForArrayInt: [100, 200, 300, 400],
    keyForArrayDouble: [0.1, 0.2],
    keyForArrayObject: [{ obj1: 'aaa' }, { obj2: 100 }],
  },
};


context.startAbility(want, (err) => {
  console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
});

import fs from '@ohos.file.fs';        
import common from '@ohos.app.ability.common';
import Want from '@ohos.app.ability.Want';
import { BusinessError } from '@ohos.base';


let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext


let fd: number = 0;
try {
  fd = fs.openSync('/data/storage/el2/base/haps/pic.png').fd;
} catch(err) {
  let code = (err as BusinessError).code;
  let message = (err as BusinessError).message;
  console.error(`Failed to openSync. Code: ${code}, message: ${message}`);
}
let want: Want = {
  deviceId: '', // An empty deviceId indicates the local device.
  bundleName: 'com.example.myapplication',
  abilityName: 'FuncAbility',
  moduleName: 'entry', // moduleName is optional.
  parameters: {
    'keyFd': { 'type': 'FD', 'value': fd } // {'type':'FD', 'value':fd} is a fixed usage, indicating that the data is a file descriptor.
  }
};


context.startAbility(want, (err) => {
  console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
});

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.

    // (1) UIAbility1 starts a ServiceExtensionAbility.
    import common from '@ohos.app.ability.common';
    import Want from '@ohos.app.ability.Want';


    let context = getContext(this) as common.UIAbilityContext; // UIAbilityContext
    let want: Want = {
      bundleName: 'com.example.myapplication1',
      abilityName: 'ServiceExtensionAbility',
    };
    context.startAbility(want, (err) => {
      console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
    });

    // (2) The ServiceExtensionAbility starts UIAbility2, carrying **"ability.params.backToOtherMissionStack": true** during the startup.
    import common from '@ohos.app.ability.common';
    import Want from '@ohos.app.ability.Want';


    let context = getContext(this) as common.ServiceExtensionContext; // ServiceExtensionContext
    let want: Want = {
      bundleName: 'com.example.myapplication2',
      abilityName: 'MainAbility',
      parameters: {
        "ability.params.backToOtherMissionStack": true,
      },
    };


    context.startAbility(want, (err) => {
      console.error(`Failed to startAbility. Code: ${err.code}, message: ${err.message}`);
    });

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.