harmony 鸿蒙@ohos.app.ability.ApplicationStateChangeCallback (ApplicationStateChangeCallback)
@ohos.app.ability.ApplicationStateChangeCallback (ApplicationStateChangeCallback)
The ApplicationStateChangeCallback module provides callbacks for the application context to listen for application foreground/background state changes.
NOTE
The initial APIs of this module are supported since API version 10. Newly added APIs will be marked with a superscript to indicate their earliest API version. The APIs of this module can be used only in the stage model.
Modules to Import
import ApplicationStateChangeCallback from '@ohos.app.ability.ApplicationStateChangeCallback';
ApplicationStateChangeCallback.onApplicationForeground
onApplicationForeground(): void;
Called when the application is switched from the background to the foreground.
System capability: SystemCapability.Ability.AbilityRuntime.AbilityCore
Example
import UIAbility from '@ohos.app.ability.UIAbility';
import ApplicationStateChangeCallback from '@ohos.app.ability.ApplicationStateChangeCallback';
let applicationStateChangeCallback: ApplicationStateChangeCallback = {
onApplicationForeground() {
console.info('applicationStateChangeCallback onApplicationForeground');
},
onApplicationBackground() {
console.info('applicationStateChangeCallback onApplicationBackground');
}
}
export default class MyAbility extends UIAbility {
onCreate() {
console.log('MyAbility onCreate');
// 1. Obtain an applicationContext object.
let applicationContext = this.context.getApplicationContext();
// 2. Use applicationContext.on() to subscribe to the 'applicationStateChange' event.
if (applicationContext != undefined) {
applicationContext.on('applicationStateChange', applicationStateChangeCallback);
}
}
onDestroy() {
let applicationContext = this.context.getApplicationContext();
// 1. Use applicationContext.off() to unsubscribe from the 'applicationStateChange' event.
if (applicationContext != undefined) {
applicationContext.off('applicationStateChange', applicationStateChangeCallback);
}
}
}
ApplicationStateChangeCallback.onApplicationBackground
onApplicationBackground(): void;
Called when the application is switched from the foreground to the background.
System capability: SystemCapability.Ability.AbilityRuntime.AbilityCore
Example
import UIAbility from '@ohos.app.ability.UIAbility';
import ApplicationStateChangeCallback from '@ohos.app.ability.ApplicationStateChangeCallback';
let applicationStateChangeCallback: ApplicationStateChangeCallback = {
onApplicationForeground() {
console.info('applicationStateChangeCallback onApplicationForeground');
},
onApplicationBackground() {
console.info('applicationStateChangeCallback onApplicationBackground');
}
}
export default class MyAbility extends UIAbility {
onCreate() {
console.log('MyAbility onCreate');
// 1. Obtain an applicationContext object.
let applicationContext = this.context.getApplicationContext();
// 2. Use applicationContext.on() to subscribe to the 'applicationStateChange' event.
if (applicationContext != undefined) {
applicationContext.on('applicationStateChange', applicationStateChangeCallback);
}
console.log('Resgiter applicationStateChangeCallback');
}
onDestroy() {
let applicationContext = this.context.getApplicationContext();
// 1. Use applicationContext.off() to unsubscribe from the 'applicationStateChange' event.
if (applicationContext != undefined) {
applicationContext.off('applicationStateChange', applicationStateChangeCallback);
}
}
}
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