@ohos.app.ability.AbilityConstant (AbilityConstant)
一、說明
AbilityConstant提供Ability相關的枚舉，包括設置初次啟動原因、上次退出原因、遷移結果、窗口類型等。本模塊首批接口從API version 9開始支持。后續版本的新增接口，采用上角標單獨標記接口的起始版本。本模塊接口僅可在Stage模型下使用。
二、導入模塊
import AbilityConstant from ‘@ohos.app.ability.AbilityConstant’;
三、屬性
1.AbilityConstant.LaunchParam
啟動參數。
系統能力：以下各項對應的系統能力均為SystemCapability.Ability.AbilityRuntime.Core
?

2.AbilityConstant.LaunchReason
Ability初次啟動原因，該類型為枚舉，可配合Ability的onCreate(want, launchParam)方法根據launchParam.launchReason的不同類型執行相應操作。
系統能力：以下各項對應的系統能力均為SystemCapability.Ability.AbilityRuntime.Core
?

示例：
import UIAbility from ‘@ohos.app.ability.UIAbility’;

class MyAbility extends UIAbility {
onCreate(want, launchParam) {
if (launchParam.launchReason === AbilityConstant.LaunchReason.START_ABILITY) {
console.log(‘The ability has been started by the way of startAbility.’);
}
}
}
3.AbilityConstant.LastExitReason
Ability上次退出原因，該類型為枚舉，可配合Ability的onCreate(want, launchParam)方法根據launchParam.lastExitReason的不同類型執行相應操作。
系統能力：以下各項對應的系統能力均為SystemCapability.Ability.AbilityRuntime.Core
?

示例：
import UIAbility from ‘@ohos.app.ability.UIAbility’;

class MyAbility extends UIAbility {
onCreate(want, launchParam) {
if (launchParam.lastExitReason === AbilityConstant.LastExitReason.ABILITY_NOT_RESPONDING) {
console.log(‘The ability has exit last because the ability was not responding.’);
}
}

4.AbilityConstant.OnContinueResult
Ability遷移結果，該類型為枚舉，可配合Ability的onContinue(wantParam)方法進完成相應的返回。
系統能力：以下各項對應的系統能力均為SystemCapability.Ability.AbilityRuntime.Core
?

示例：
import UIAbility from ‘@ohos.app.ability.UIAbility’;

class MyAbility extends UIAbility {
onContinue(wantParam) {
return AbilityConstant.OnContinueResult.AGREE;
}
}
5.AbilityConstant.MemoryLevel
內存級別，該類型為枚舉，可配合Ability的onMemoryLevel(level)方法根據level執行不同內存級別的相應操作。
系統能力：以下各項對應的系統能力均為SystemCapability.Ability.AbilityRuntime.Core
?

示例：
import UIAbility from ‘@ohos.app.ability.UIAbility’;

class MyAbility extends UIAbility {
onContinue(wantParam) {
return AbilityConstant.OnContinueResult.AGREE;
}
}
6.AbilityConstant.MemoryLevel
內存級別，該類型為枚舉，可配合Ability的onMemoryLevel(level)方法根據level執行不同內存級別的相應操作。
系統能力：以下各項對應的系統能力均為SystemCapability.Ability.AbilityRuntime.Core
?

示例：
import UIAbility from ‘@ohos.app.ability.UIAbility’;

class MyAbility extends UIAbility {
onSaveState(reason, wantParam) {
return AbilityConstant.OnSaveResult.ALL_AGREE;
}
}
7.AbilityConstant.StateType
保存應用數據場景原因，該類型為枚舉，可配合Ability的onSaveState(reason, wantParam)方法根據reason的不同類型執行相應操作。
系統能力：以下各項對應的系統能力均為SystemCapability.Ability.AbilityRuntime.Core
?

示例：
import UIAbility from ‘@ohos.app.ability.UIAbility’;

class MyAbility extends UIAbility {
onSaveState(reason, wantParam) {
if (reason === AbilityConstant.StateType.CONTINUATION) {
console.log(‘Save the ability data when the ability continuation.’);
}
return AbilityConstant.OnSaveResult.ALL_AGREE;
}
}

本文根據HarmonyOS官方開發文檔整理