Self-study HarmonyOS application development (56) - Use Service to ensure that the application runs continuously in the background

秒表程序的功能当然是计时,但是Harmony应用的默认动作是切到后台之后程序会退出,无法实现连续计时.首先来看效果视频：

创建Service类

首先创建一个Ability的子类StopWatchService：

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       public class StopWatchService extends Ability {    private static final int NOTIFICATION_ID = 0XD0000002;    private static final String TAG = StopWatchService.class.getSimpleName();    private static final HiLogLabel LABEL_LOG = new HiLogLabel(3, 0x00209, TAG);    private static final String DESCRIPTOR = "xwg.harmony.stopwatch.StopWatchService";
       
       
    @Override    public void onStart(Intent intent) {        HiLog.info(LABEL_LOG, "StopWatchService.onStart!");        startForeground();        super.onStart(intent);    }
       
       
    @Override    public void onCommand(Intent intent, boolean restart, int startId) {        HiLog.info(LABEL_LOG, "StopWatchService.onCommand!");        super.onCommand(intent, restart, startId);    }
       
       
    @Override    public IRemoteObject onConnect(Intent intent) {        HiLog.info(LABEL_LOG, "StopWatchService.onConnect!");        return remoteAgentStub;    }
       
       
    @Override    public void onDisconnect(Intent intent) {        HiLog.info(LABEL_LOG, "StopWatchService.onDisconnect!");        super.onDisconnect(intent);    }
       
       
    @Override    public void onStop() {        HiLog.info(LABEL_LOG, "StopWatchService.onStop()<<<<<<<<<<<<<<<<<!");        super.onStop();        cancelBackgroundRunning();    }
       
       
    private void startForeground() {        NotificationRequest request = new NotificationRequest(NOTIFICATION_ID).setTapDismissed(true);        NotificationRequest.NotificationNormalContent content = new NotificationRequest.NotificationNormalContent();        content.setTitle("秒表服务").setText("前台服务运行中...");        NotificationRequest.NotificationContent notificationContent = new NotificationRequest.NotificationContent(                content);        request.setContent(notificationContent);        keepBackgroundRunning(NOTIFICATION_ID, request);    }}
      
      
      
      

       
       
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关于重写的几个方法的详细信息,请参照文后链接【创建Service】;startForground和cancelBackgroundRunning方法用于开启和关闭前台Service模式,具体说明请参照文后链接【前台Service】,这里不再一一赘述.

注册Service类

修改config.json文件,增加StopWatchService相关内容.

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       "module": {  "abilities": [    {      "backgroundModes": [        "dataTransfer",        "location"      ],      "name": "xwg.harmony.stopwatch.StopWatchService",      "icon": "$media:icon",      "description": "$string:stopwatchservice_description",      "type": "service",      "visible": true    }  ],}
      
      
      
      

       
       
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最主要的是type信息.

启动Service

在需要启动StopWatchService的画面中调用下面的startLocalService方法即可启动Service.两个常量就是我们启动StopWatchService时需要的参数.

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       private static final String LOCAL_BUNDLE = "xwg.harmony.stopwatch";private static final String FOREGROUND_SERVICE = "StopWatchService";
       
       
private void startLocalService(String bundleName, String serviceName) {    Intent intent = getLocalServiceIntent(LOCAL_BUNDLE, FOREGROUND_SERVICE);    startAbility(intent);}
       
       
private Intent getLocalServiceIntent(String bundleName, String serviceName) {        Operation operation = new Intent.OperationBuilder().withDeviceId("")                .withBundleName(bundleName)                .withAbilityName(serviceName)                .build();        Intent intent = new Intent();        intent.setOperation(operation);        return intent;    }
      
      
      
      

       
       
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具体说明请参照文后链接【启动Service】.

参考代码

完整代码可以从以下链接下载：

​ ​https://github.com/xueweiguo/Harmony/tree/master/StopWatch​​

参考资料：

Service Ability基本概念

​ ​https://developer.harmonyos.com/cn/docs/documentation/doc-​​

guides/ability-service-concept-0000000000044457

创建Service

​ ​https://developer.harmonyos.com/cn/docs/documentation/doc-guides/ability-service-creating-0000000000044464​​

前台Service

​ ​https://developer.harmonyos.com/cn/docs/documentation/doc-guides/ability-service-foreground-0000000000044473​​

启动Service

​ ​https://developer.harmonyos.com/cn/docs/documentation/doc-guides/ability-service-starting-0000000000044465​​

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