harmony 鸿蒙PageAbility Launch Type

2023-02-03
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PageAbility Launch Type

Depending on the launch type, the action performed when the PageAbility starts differs, as described in the table below.

Table 1 PageAbility launch types

Launch Type	Meaning	Description
singleton	Singleton mode	Each time startAbility() is called, if an ability instance of this type already exists in the application process, the instance is reused. There is only one ability instance of this type in Recents. A typical scenario is as follows: When a user opens a video playback application and watches a video, returns to the home screen, and opens the video playback application again, the video that the user watched before returning to the home screen is still played.
standard	Multiton mode	Default type. Each time startAbility() is called, a new ability instance is created in the application process. Multiple ability instances of this type are displayed in Recents. A typical scenario is as follows: When a user opens a document application and touches New, a new document task is created. Multiple new document missions are displayed in Recents.

You can set launchType in the config.json file to configure the launch type. The sample code is as follows:

{
  "module": {
    ...
    "abilities": [
      {
        // singleton means the singleton mode.
        // standard means the multiton mode.
        "launchType": "standard",
        ...
      }
    ]
  }
}

When the PageAbility is started in multiton mode or it is started in singleton mode for the first time, the PageAbility lifecycle callbacks are triggered. When it is not started for the first time in singleton mode, the onNewWant() callback (as described in the table below) is triggered, but the onCreate() callback is not.

Table 2 Callbacks specific to the singleton mode

API	Description
onNewWant(want: Want)	onNewWant() is triggered when the PageAbility is not started for the first time in singleton mode. You can obtain Want from this callback and perform further processing based on Want. For example, in the singleton PageAbility migration scenario, you can specify a page to start the PageAbility.