Component Startup Rules (Stage Model)

Component startup refers to the behavior of starting or connecting to an application component.

• Start the UIAbility, ServiceExtensionAbility, and DataShareExtensionAbility components. For example, you can use startAbility(), startServiceExtensionAbility(), and startAbilityByCall().

• Connect to the ServiceExtensionAbility and DataShareExtensionAbility components. For example, you can use connectServiceExtensionAbility() and createDataShareHelper().

General Component Startup Rules

To deliver a better user experience, the system restricts the following behavior:

• A background application randomly displays a dialog box, such as an ads pop-up.

• Background applications wake up each other. This type of behavior occupies system resources and increases power consumption, or even causes system frozen.

• A foreground application randomly redirects to another application, for example, redirecting to the payment page of another application. This type of behavior poses security risks.

In view of this, the system formulates a set of component startup rules, as follows:

• Before starting a component of another application, check whether the component can be called by others.

  If the exported field of the component is set to true, the component can be called by other applications. If the field is set to false, the component cannot be called by other applications. If this is the case, you must also verify the ohos.permission.START_INVISIBLE_ABILITY permission. For details about the exported fields, see abilities.

• Before starting a UIAbility component of a background application, verify the permission ohos.permission.START_ABILITIES_FROM_BACKGROUND.

  NOTE

  An application is considered as a foreground application only when the application process gains focus or its UIAbility component is running in the foreground.

• Before using startAbilityByCall() to start a component, verify the permission ohos.permission.ABILITY_BACKGROUND_COMMUNICATION.

The preceding component startup rules take effect since API version 9. Familiarity with these rules helps you prevent service function exceptions.

Intra-Device Component Startup Rules

The rules for starting components on the same device vary in the following scenarios:

• Starting the UIAbility component

• Starting the ServiceExtensionAbility and DataShareExtensionAbility components

• Using startAbilityByCall() to start the UIAbility component

Inter-Device Component Startup Rules

The rules for starting components on a different device vary in the following scenarios:

• Starting the UIAbility component

• Starting the ServiceExtensionAbility and DataShareExtensionAbility components

• Using startAbilityByCall() to start the UIAbility component