鸿蒙6.0应用开发——实况窗开发

将LiveViewLockScreenExtensionAbility的名称写入创建实况窗时创建的liveView对象中。

import { liveViewManager } from '@kit.LiveViewKit';
// …
// Construct live window request body.
let liveView: liveViewManager.LiveView = {
id: 0,
sequence: this.sequence,
// Application scenarios of the live window. NAVIGATION: Navigation.
event: 'NAVIGATION',
liveViewData: {
// Live view capsule related parameters
capsule: {
type: liveViewManager.CapsuleType.CAPSULE_TYPE_TEXT,
status: 1,
icon: 'turn_right_light_square.png',
backgroundColor: this.getStringSync($r('app.string.live_view_background').id),
title: this.getStringSync($r('app.string.live_view_title').id),
},
// Live view card related parameters
primary: {
title: this.getStringSync($r('app.string.live_view_title').id),
content: [{ text: this.getStringSync($r('app.string.live_view_content').id) }],
// Add LiveViewLockScreenExtensionAbility name to build lock screen live view
liveViewLockScreenAbilityName: 'LiveViewExtAbility',
liveViewLockScreenAbilityParameters: { liveViewParameters: '' },
keepTime: 0,
clickAction: await LiveViewUtil.buildWantAgent()
}
}
};

在应用module.json5中配置LiveViewLockScreenExtensionAbility的名称。

"extensionAbilities": [
{
// Keep it consistent with LiveViewLockScreenExtensionAbility name in live view instance
"name": "LiveViewExtAbility",
"type": "liveViewLockScreen",
// LiveViewLockScreenExtensionAbility location
"srcEntry": "./ets/liveview/LiveViewExtAbility.ets",
"exported": false
}
],

在LiveViewLockScreenExtensionAbility的onSessionCreate()方法中完成锁屏沉浸实况窗页面的创建。

// Core logic when creating UI session.
onSessionCreate(_want: Want, session: UIExtensionContentSession): void {
// …
try {
session.loadContent('liveview/LockScreenPage');
} catch (error) {
const err: BusinessError = error as BusinessError;
hilog.error(0x0000, TAG, `Session load content failed. code: ${err.code}, message: ${err.message}`);
}
}

• 优点：实现简单，支持跨进程广播通信。
• 缺点：无法获取初始数据。

• 优点：启动时可立即获取初始数据。
• 缺点：数据不可更新，更新需重启锁屏沉浸实况窗，可能导致闪屏。

• 优点：适合大数据量传输，可持久化存储。
• 缺点：读写文件效率较低，锁屏沉浸实况窗进程无法直接获取沙箱路径，需由应用主进程通过其他方式传入沙箱路径。

申请后台长时任务，确保在后台能够发布公共事件以传递更新数据。

• 在申请后台长时任务之前，需确认应用已在module.json5中声明后台运行权限。

  "requestPermissions": [
  {
  "name": "ohos.permission.KEEP_BACKGROUND_RUNNING",
  "reason": "$string:reason_background",
  "usedScene": {
  "abilities": [
  "EntryAbility"
  ],
  "when": "always"
  }
  },
  ],

• 应用创建长时任务，并声明长时任务类型。

  import { backgroundTaskManager } from '@kit.BackgroundTasksKit';
  // …
  // Internal method to manage background tasks
  private startContinuousRunningTask() {
  // Configure WantAgent for background operation
  let wantAgentInfo: wantAgent.WantAgentInfo = {
  wants: [
  {
  bundleName: 'com.example.mapliveviewsample',
  abilityName: 'EntryAbility'
  }
  ],
  actionType: wantAgent.OperationType.START_ABILITY,
  requestCode: 0,
  actionFlags: [wantAgent.WantAgentFlags.UPDATE_PRESENT_FLAG]
  };

  try {
  // Acquire WantAgent for background operations
  wantAgent.getWantAgent(wantAgentInfo).then((wantAgentObj: WantAgent) => {
  try {
  hilog.info(0x0000, TAG, '%{public}s', 'Operation startBackgroundRunning begin.');
  // Required background resource types
  const list: string[] = ['location'];
  // Request background running permission
  if (canIUse('SystemCapability.ResourceSchedule.BackgroundTaskManager.ContinuousTask')) {
  backgroundTaskManager.startBackgroundRunning(this.context, list, wantAgentObj).then(() => {
  hilog.info(0x0000, TAG, '%{public}s', 'Operation startBackgroundRunning succeeded.');
  }).catch((error: BusinessError) => {
  hilog.error(0x0000, TAG, '%{public}s',
  `Failed to Operation startBackgroundRunning. code is ${error.code} message is ${error.message}`);
  });
  }
  } catch (error) {
  hilog.error(0x0000, TAG, '%{public}s',
  `Failed to Operation startBackgroundRunning. code is ${(error as BusinessError).code} message is ${(error as BusinessError).message}`);
  }
  });
  } catch (error) {
  hilog.error(0x0000, TAG, '%{public}s',
  `Failed to Operation getWantAgent. code is ${(error as BusinessError).code} message is ${(error as BusinessError).message}`);
  }
  }

  代码逻辑走读：

• 导入模块：代码首先从@kit.BackgroundTasksKit模块中导入backgroundTaskManager，用于管理后台任务。
• 内部方法定义：定义了一个名为startContinuousRunningTask的私有方法，用于启动持续运行的后台任务。
• 配置WantAgent：创建一个wantAgentInfo对象，用于配置WantAgent，以便在后台执行特定操作。
• 获取WantAgent对象：使用wantAgent.getWantAgent方法获取WantAgent对象，该方法是异步的，返回一个Promise。
• 日志记录：在尝试开始后台运行任务之前，使用hilog.info记录日志信息，表示开始操作。
• 请求后台运行权限：检查系统是否支持SystemCapability.ResourceSchedule.BackgroundTaskManager.ContinuousTask，如果支持，则调用backgroundTaskManager.startBackgroundRunning方法启动后台运行任务。
• 处理成功和错误情况：在启动后台运行任务的Promise中，使用.then处理成功情况，使用.catch处理错误情况，并通过hilog.error记录错误信息。
• 错误处理：在获取WantAgent对象的Promise中，也使用.catch处理错误情况，并通过hilog.error记录错误信息。

发布公共事件传递更新数据到锁屏沉浸实况窗。

应用在主页面中通过commonEventManager.publish()接口发布公共事件’live_view_lock_screen’，并在CommonEventPublishData的parameters属性中附带锁屏沉浸实况窗的创建和更新数据。

import { BusinessError, commonEventManager } from '@kit.BasicServicesKit';
// …
// Prepare common event data
let options: commonEventManager.CommonEventPublishData = {
data: 'data',
bundleName: 'com.example.mapliveviewsample',
parameters: {
'laneData': routeData.laneData
}
};
// Publish system event for lock screen updates
commonEventManager.publish('live_view_lock_screen', options, (error: BusinessError) => {
if (error) {
hilog.error(0x0000, TAG, '%{public}s',
`Failed to publish commonEvent. code is ${error.code} message is ${error.message}`);
} else {
hilog.info(0x0000, TAG, '%{public}s', 'Succeeded in publishing commonEvent.')
}
});

订阅公共事件更新锁屏沉浸实况窗。

锁屏沉浸实况窗进程在LiveViewLockScreenExtensionAbility中，使用commonEventManager.createSubscriber()接口创建主页面创建的公共事件’live_view_lock_screen’的订阅者，通过AppStorage（应用全局的UI状态存储）将主页面传递的数据传入LockScreenPage.ets，以实现锁屏沉浸实况窗的创建和更新。

import { BusinessError, commonEventManager } from '@kit.BasicServicesKit';
// …

// Initialize event subscription.
let subscribeInfo: commonEventManager.CommonEventSubscribeInfo = {
events: ['live_view_lock_screen'],
publisherBundleName: 'com.example.mapliveviewsample',
priority: 0
};
commonEventManager.createSubscriber(subscribeInfo,
(error: BusinessError, data: commonEventManager.CommonEventSubscriber) => {
if (error) {
hilog.error(0x0000, TAG, '%{public}s',
`Failed to create subscriber. code is ${error.code} message is ${error.message}.`);
return;
}
this.subscriber = data;
hilog.info(0x0000, TAG, '%{public}s', 'Succeeded in creating subscriber.');
// Event handling logic.
commonEventManager.subscribe(this.subscriber,
async (error: BusinessError, data: commonEventManager.CommonEventData) => {
if (error) {
hilog.error(0x0000, TAG, '%{public}s',
`Failed to subscribe commonEvent. code is ${error.code} message is ${error.message}.`);
return;
}
hilog.info(0x0000, TAG, '%{public}s', 'Succeeded in subscribe commonEvent success.');
if (data.parameters) {
let laneData = data.parameters['laneData'] as LaneData;
AppStorage.setOrCreate('laneData', laneData);
hilog.info(0x0000, TAG, '%{public}s', 'Succeeded in receive commonEvent.');
}
});
})

代码逻辑走读：

• 从’@kit.BasicServicesKit’导入BusinessError和commonEventManager。

• 创建一个subscribeInfo对象，指定要订阅的事件名称为’live_view_lock_screen’，并设置发布者包名和优先级。

• 调用commonEventManager.createSubscriber方法，传入subscribeInfo和回调函数。
• 如果创建订阅者失败，记录错误日志并返回。
• 如果成功，将返回的订阅者对象赋值给this.subscriber，并记录成功日志。

• 调用commonEventManager.subscribe方法，传入订阅者对象和回调函数。
• 如果订阅失败，记录错误日志并返回。
• 如果订阅成功，记录成功日志。

• 检查事件数据中是否包含参数laneData。
• 如果存在，将其转换为LaneData类型，并存储到AppStorage中。
• 记录接收事件的日志。

停止数据源接收：关闭数据输入通道，停止数据采集。本开发实践为结束定时器任务，停止更新车道数据。

// Clear periodic updates
if (this.updateInterval !== undefined) {
clearInterval(this.updateInterval);
this.updateInterval = undefined;
hilog.info(0x0000, TAG, 'Timer has been cleared');
}

结束界面更新：停止实况窗和沉浸实况窗的内容更新与展示。

// Close live view.
public async closeLiveView() {
// Ensure that the sequence is greater than the current live window page.
this.sequence++;
this.defaultLiveView = await this.createPrimaryLiveView();
await liveViewManager.stopLiveView(this.defaultLiveView).then(() => {
this.sequence = 0;
this.defaultLiveView = undefined;
hilog.info(0x0000, TAG, '%{public}s', 'Succeeded in stopping liveView, result: %{public}');
}).catch((error: BusinessError) => {
hilog.error(0x0000, TAG, '%{public}s',
`Failed to stop liveView. Cause code: ${error.code}, message: ${error.message}`);
});
return;
}

清理后台任务：结束关联的后台长时运行任务。

// Stop background tasks
try {
if (canIUse('SystemCapability.ResourceSchedule.BackgroundTaskManager.ContinuousTask')) {
backgroundTaskManager.stopBackgroundRunning(this.context).then(() => {
hilog.info(0x0000, TAG, '%{public}s', 'Operation stopBackgroundRunning succeeded');
}).catch((error: BusinessError) => {
hilog.error(0x0000, TAG, '%{public}s',
`Operation stopBackgroundRunning failed. code is ${error.code} message is ${error.message}`);
});
}
} catch (error) {
hilog.error(0x0000, TAG, '%{public}s',
`Operation stopBackgroundRunning failed. code is ${(error as BusinessError).code} message is ${(error as BusinessError).message}`);
}