# @ohos.app.ability.appRecovery

The **appRecovery** module provides APIs for recovering faulty applications.

> **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. In the current version, only applications with a single ability in a single process can be recovered.

## Modules to Import
```ts
import appRecovery from '@ohos.app.ability.appRecovery'
```


## appRecovery.RestartFlag

Enumerates the application restart options used in [enableAppRecovery](#apprecoveryenableapprecovery).

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

| Name                         | Value  | Description                                                        |
| ----------------------------- | ---- | ------------------------------------------------------------ |
| ALWAYS_RESTART           | 0    | The application is restarted in all cases.|
| CPP_CRASH_NO_RESTART           | 0x0001    | The application is not restarted in the case of CPP_CRASH.|
| JS_CRASH_NO_RESTART           | 0x0002    | The application is not restarted in the case of JS_CRASH.|
| APP_FREEZE_NO_RESTART           | 0x0004    | The application is not restarted in the case of APP_FREEZE.|
| NO_RESTART           | 0xFFFF  | The application is not restarted in any case.|

## appRecovery.SaveOccasionFlag

Enumerates the scenarios for saving the application state, which is used in [enableAppRecovery](#apprecoveryenableapprecovery).

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

| Name                         | Value  | Description                                                        |
| ----------------------------- | ---- | ------------------------------------------------------------ |
| SAVE_WHEN_ERROR            | 0x0001    | Saving the application state when an application fault occurs.|
| SAVE_WHEN_BACKGROUND            | 0x0002    | Saving the application state when the application is switched to the background.|

## appRecovery.SaveModeFlag  

Enumerates the application state saving modes used in [enableAppRecovery](#apprecoveryenableapprecovery).

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

| Name                         | Value  | Description                                                        |
| ----------------------------- | ---- | ------------------------------------------------------------ |
| SAVE_WITH_FILE             | 0x0001    | The application state is saved and written to the local file cache.|
| SAVE_WITH_SHARED_MEMORY             | 0x0002    | The application state is saved in the memory. When the application exits due to a fault, it is written to the local file cache.|

## appRecovery.enableAppRecovery

enableAppRecovery(restart?: RestartFlag, saveOccasion?: SaveOccasionFlag, saveMode?: SaveModeFlag) : void;

Enables application recovery.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**

| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| restart | [RestartFlag](#apprecoveryrestartflag) | No| Whether the application is restarted upon a fault. By default, the application is not restarted.|
| saveOccasion | [SaveOccasionFlag](#apprecoverysaveoccasionflag) | No| Scenario for saving the application state. By default, the state is saved when a fault occurs.|
| saveMode | [SaveModeFlag](#apprecoverysavemodeflag) | No| Application state saving mode. By default, the application state is written to the local file cache.|

**Example**
    
```ts
export default class MyAbilityStage extends AbilityStage {
    onCreate() {
        appRecovery.enableAppRecovery(RestartFlag::ALWAYS_RESTART, SaveOccasionFlag::SAVE_WHEN_ERROR, SaveModeFlag::SAVE_WITH_FILE);
    }
}
```

## appRecovery.restartApp

restartApp(): void;

Restarts the application. This API can be used together with APIs of [errorManager](js-apis-app-ability-errorManager.md).

**System capability**: SystemCapability.Ability.AbilityRuntime.Core


**Example**
    
```ts
var observer = {
    onUnhandledException(errorMsg) {
        console.log('onUnhandledException, errorMsg: ', errorMsg)
        appRecovery.restartApp();
    }
}

```

## appRecovery.saveAppState

saveAppState(): boolean;

Saves the application state. This API can be used together with APIs of [errorManager](js-apis-app-ability-errorManager.md).

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Return value**

| Type| Description|
| -------- | -------- |
| boolean | Whether the saving is successful.|

**Example**
    
```ts
var observer = {
    onUnhandledException(errorMsg) {
        console.log('onUnhandledException, errorMsg: ', errorMsg)
        appRecovery.saveAppState();
    }
}
```