目录

应用接续数据迁移

概述

在应用接续实践过程中，需要选择合适的数据迁移方案进行迁移，迁移方案的选择与数据大小和是否涉及文件迁移有直接关系，选择方案如下：

  

<100kb

>100kb

需要文件迁移

文件资产迁移

文件资产迁移

不需要文件迁移

使用want.param数据迁移

基础数据迁移

实现原理

实现原理见运作机制。

开发步骤

接入应用接续需要启用应用接续能力、配置应用启动模式类型、源端保存迁移数据和对端恢复数据，具体开发流程见应用接续概述，本文只关注在不同场景下迁移数据方案的选择。

使用want.param数据迁移

  1. 源端保存迁移数据
    export default class EntryAbility extends UIAbility {
  // ...
  async onContinue(wantParam: Record<string, Object | undefined>): Promise<AbilityConstant.OnContinueResult> {
    // ...
    // Migrate simple data using wantParam.param
    wantParam.wantBasicData = AppStorage.get('wantBasicData');
    // ...
    // Return AGREE to allow cross-device migration
    return AbilityConstant.OnContinueResult.AGREE;
  }
  // ...
}
  2. 对端恢复数据
    export default class EntryAbility extends UIAbility {
  private distributedObject: distributedDataObject.DataObject | undefined = undefined;
  private storage: LocalStorage = new LocalStorage();
  private distributedFileUtil: DistributedFileUtil | undefined = undefined;
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    hilog.info(DOMAIN, TAG, FORMAT, `Ability onCreate`);
    this.distributedFileUtil = new DistributedFileUtil(this.context);
    this.appContinuity(want, launchParam);
  }

  onNewWant(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    hilog.info(DOMAIN, TAG, FORMAT, `Ability onNewWant`);
    this.appContinuity(want, launchParam);
  }

  appContinuity(want: Want, launchParam: AbilityConstant.LaunchParam) {
    if (launchParam.launchReason === AbilityConstant.LaunchReason.CONTINUATION) {
      if (want.parameters !== undefined) {
        // Use want.param to migrate the simple data page data
        AppStorage.setOrCreate('wantBasicData', want.parameters.wantBasicData);
      }
      // ...
      try {
        // Restore window stage with new LocalStorage instance
        this.context.restoreWindowStage(this.storage);
      } catch (err) {
        hilog.error(DOMAIN, TAG, FORMAT, `RestoreWindowStage failed. Cause : ${err}`);
      }
    }
  }

  // ...
}

使用分布式对象迁移数据

[h2]基础数据迁移

  1. 源端保存迁移数据

    在源端UIAbility的onContinue()接口中创建分布式数据对象并保存数据，执行流程如下：

    1. 在onContinue()接口中使用create()接口创建分布式数据对象，将所要迁移的数据填充到分布式数据对象中。
    2. 调用genSessionId()接口生成分布式数据对象组网id，分布式数据对象调用setSessionId()方法将id传入，激活分布式数据对象。
    3. 使用save()接口将已激活的分布式数据对象持久化，确保源端退出后对端依然可以获取到数据。
    4. 将生成的sessionId通过want传递到对端，供对端激活同步使用。
    • 分布式数据对象需要先激活，再持久化，因此必须在调用setSessionId()后再调用save()接口。
    • 对于源端迁移后需要退出的应用，为了防止数据未保存完成应用就退出，应采用await的方式等待save()接口执行完毕。从API12起，onContinue()接口提供了async版本供该场景使用。
    • 当前，wantParams中“sessionId”字段在迁移流程中被系统占用，建议开发者在wantParams中定义其他key值存储该分布式数据对象生成的id，避免数据异常。
    export class ContinuationData {
  public basicDataStr: string | undefined;
  public basicDataNum: number | undefined;
  public distributedData: DistributedData | undefined;
  // ...
  constructor(
    basicDataStr: string | undefined,
    basicDataNum: number | undefined,
    distributedData: DistributedData | undefined,
    // ...
  ) {
    this.basicDataStr = basicDataStr;
    this.basicDataNum = basicDataNum;
    this.distributedData = distributedData;
    // ...
  }
  // ...
}
    export default class EntryAbility extends UIAbility {
  private distributedObject: distributedDataObject.DataObject | undefined = undefined;
  private storage: LocalStorage = new LocalStorage();
  private distributedFileUtil: DistributedFileUtil | undefined = undefined;
  // ...
  async onContinue(wantParam: Record<string, Object | undefined>): Promise<AbilityConstant.OnContinueResult> {
    if (!this.distributedFileUtil) {
      return AbilityConstant.OnContinueResult.REJECT;
    }
    // ...
    let sessionId: string = distributedDataObject.genSessionId();
    wantParam.distributedSessionId = sessionId;
    // ...
    let contentInfo: ContinuationData = new ContinuationData(
      AppStorage.get('basicDataStr') ?? '',
      AppStorage.get('basicDataNum') ?? undefined,
      AppStorage.get('distributedData') ?? undefined,
      // ...
      (AppStorage.get('pageInfos') as NavPathStack).getAllPathName()[0]
    );
    let source = await contentInfo.flatAssets();
    this.distributedObject = distributedDataObject.create(this.context, source);
    this.distributedObject.setSessionId(sessionId).catch((err: BusinessError) => {
      hilog.info(DOMAIN, TAG, FORMAT, `SetSessionId failed. Cause code: ${err.code}`);
    });
    await this.distributedObject.save(wantParam.targetDevice as string).catch((err: BusinessError) => {
      hilog.info(DOMAIN, TAG, FORMAT, `Failed to save. Code: ${err.code}`);
    });
    // Return AGREE to allow cross-device migration
    return AbilityConstant.OnContinueResult.AGREE;
  }
  // ...
}
  2. 对端恢复数据

    在对端UIAbility的onCreate()/onNewWant()中，通过加入与源端一致的分布式数据对象组网进行数据恢复。执行流程如下：

    1. 创建空的分布式数据对象，用于接收恢复的数据；
    2. 从want中读取分布式数据对象组网id；
    3. 注册on()接口监听数据变更。在收到status为restored的事件的回调中，实现数据恢复完毕时需要进行的业务操作。
    4. 调用setSessionId()加入组网，激活分布式数据对象。
    • 对端加入组网的分布式数据对象不能为临时变量，因为分布式数据对象on()接口为异步回调，可能在onCreate()/onNewWant()执行结束后才执行，临时变量被释放可能导致空指针异常。可以使用类成员变量避免该问题。
    • 对端用于创建分布式数据对象，其属性应在激活分布式数据对象设置为undefined，否则会导致新数据加入组网后覆盖源端数据，数据恢复失败。
    • 应当在激活分布式数据对象之前，调用分布式数据对象的on()接口进行注册监听，防止错过restored事件导致数据恢复失败。
    export default class EntryAbility extends UIAbility {
  private distributedObject: distributedDataObject.DataObject | undefined = undefined;
  private storage: LocalStorage = new LocalStorage();
  private distributedFileUtil: DistributedFileUtil | undefined = undefined;
  onCreate(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    hilog.info(DOMAIN, TAG, FORMAT, `Ability onCreate`);
    this.distributedFileUtil = new DistributedFileUtil(this.context);
    this.appContinuity(want, launchParam);
  }

  onNewWant(want: Want, launchParam: AbilityConstant.LaunchParam): void {
    hilog.info(DOMAIN, TAG, FORMAT, `Ability onNewWant`);
    this.appContinuity(want, launchParam);
  }

  appContinuity(want: Want, launchParam: AbilityConstant.LaunchParam) {
    if (launchParam.launchReason === AbilityConstant.LaunchReason.CONTINUATION) {
      // ...
      let mailInfo: ContinuationData = new ContinuationData(undefined, undefined, undefined, undefined, undefined,
        undefined, undefined, undefined, undefined, undefined);
      this.distributedObject = distributedDataObject.create(this.context, mailInfo);
      // Add a data restored listener.
      try {
        this.distributedObject.on('status',
          (_sessionId: string, _networkId: string, status: 'online' | 'offline' | 'restored') => {
            if (status === 'restored') {
              if (!this.distributedObject || !this.distributedFileUtil) {
                return;
              }
              // Use the distributed object migration to transfer the basic page data
              AppStorage.setOrCreate('basicDataStr', this.distributedObject['basicDataStr'] ?? '');
              AppStorage.setOrCreate('basicDataNum', this.distributedObject['basicDataNum'] ?? undefined);
              AppStorage.setOrCreate('distributedData', this.distributedObject['distributedData'] ?? undefined);
              // ...
              AppStorage.setOrCreate('curPageInfos', this.distributedObject['curPageInfos'] ?? undefined);
            }
          });
      } catch (err) {
        hilog.error(DOMAIN, TAG, FORMAT, `On status failed. Cause code: ${err.code}`);
      }
      let sessionId: string = want.parameters?.distributedSessionId as string;
      this.distributedObject.setSessionId(sessionId).catch((err: BusinessError) => {
        hilog.info(DOMAIN, TAG, FORMAT, `SetSessionId failed. Cause code: ${err.code}`);
      });
      try {
        // Restore window stage with new LocalStorage instance
        this.context.restoreWindowStage(this.storage);
      } catch (err) {
        hilog.error(DOMAIN, TAG, FORMAT, `RestoreWindowStage failed. Cause : ${err}`);
      }
    }
  }

  // ...
}

[h2]文件资产迁移

示例代码