Harmony OS ServiceAbility学习（二）_鸿蒙 serviceability socket

ServiceAbility基本概念

其实这玩意就跟Android的Service一毛一样，Android的Service有什么特性，ServiceAbility就有什么特性，除了名字不一样，其它完全一样。所以这玩意启动后，要记得退出，耗时任务要单独开启线程。

创建Service

创建很简单，注册也很简单，基本ide会自动注册，只不过有些东西需要手动添加

public class MyServiceAbility extends Ability {
    private static final HiLogLabel LABEL_LOG = new HiLogLabel(3, 0xD001100, "MainAbility");

    @Override
    public void onStart(Intent intent) {
        HiLog.error(LABEL_LOG, "MyServiceAbility::onStart");
        super.onStart(intent);
    }

    @Override
    public void onBackground() {
        super.onBackground();
        HiLog.error(LABEL_LOG, "MyServiceAbility::onBackground");
    }

    @Override
    public void onStop() {
        super.onStop();
        HiLog.error(LABEL_LOG, "MyServiceAbility::onStop");
    }

    @Override
    public void onCommand(Intent intent, boolean restart, int startId) {
        HiLog.error(LABEL_LOG, "MyServiceAbility::onCommand");
    }

    /**
     * 返回给客户端
     * @param intent
     * @return
     */
    @Override
    public IRemoteObject onConnect(Intent intent) {
        HiLog.error(LABEL_LOG, "MyServiceAbility::onConnect");
        return new MyRemoteObject();
    }

    @Override
    public void onDisconnect(Intent intent) {
        HiLog.error(LABEL_LOG, "MyServiceAbility::onDisconnect");
    }


    //创建自定义LocalRemoteObject
    private class MyRemoteObject extends LocalRemoteObject {
        public MyRemoteObject() {
        }
    }
}
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看一下注册文件：

 {
        "name": "com.example.hmlearning.ui.MyServiceAbility",
        "icon": "$media:icon",
        "description": "$string:myserviceability_description",
        "type": "service",//类型是service
        "visible": true,//允许其他应用调用这个service
        "backgroundModes": [
          "dataTransfer",
          "audioPlayback",
          "audioRecording",
          "pictureInPicture",
          "voip",
          "location",
          "bluetoothInteraction",
          "wifiInteraction"
        ]
      }
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启动Service

非常简单，就跟Android启动差不多

启动同一设备Service

/**
 * 启动本地Service
 *
 * DeviceId:如果是本地设备，则可以直接留空；
 * 如果是远程设备，通过ohos.distributedschedule.interwork.DeviceManager提供的getDeviceList获取设备列表
 *
 * BundleName：表示包名称
 *
 * AbilityName：表示待启动的Ability名称
 *
 **/
public static void startLocalService(Ability ability) {
        Intent intent = new Intent();
        Operation operation = new Intent.OperationBuilder()
                .withDeviceId("")
                .withBundleName("com.example.hmlearning")
                .withAbilityName("com.example.hmlearning.ui.MyServiceAbility")
                .build();
        intent.setOperation(operation);
        ability.startAbility(intent);
    }
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停止同一设备Service

 /**
     * 停止service
     * @param ability
     */
    public static void stopLocalService(Ability ability){
        Intent intent = new Intent();
        Operation operation = new Intent.OperationBuilder()
                .withDeviceId("")
                .withBundleName("com.example.hmlearning")
                .withAbilityName("com.example.hmlearning.ui.MyServiceAbility")
                .build();
        intent.setOperation(operation);
        ability.stopAbility(intent);
    }
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启动远程设备Service

 	/**
 	 *
     * 启动远程service
     */
    public static void startRemoteService(Ability ability) {
        Intent intent = new Intent();
        Operation operation = new Intent.OperationBuilder()
                .withDeviceId("deviceId")
                .withBundleName("com.domainname.hiworld.himusic")
                .withAbilityName("com.domainname.hiworld.himusic.ServiceAbility")
                .withFlags(Intent.FLAG_ABILITYSLICE_MULTI_DEVICE) // 设置支持分布式调度系统多设备启动的标识
                .build();
        intent.setOperation(operation);
        ability.startAbility(intent);
    }
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停止远程设备Service

 /**
     * 停止service
     * @param ability
     */
    public static void stopRemoteService(Ability ability){
        Intent intent = new Intent();
        Operation operation = new Intent.OperationBuilder()
                .withDeviceId("")
                .withBundleName("com.example.hmlearning")
                .withAbilityName("com.example.hmlearning.ui.MyServiceAbility")
                .withFlags(Intent.FLAG_ABILITYSLICE_MULTI_DEVICE) // 设置支持分布式调度系统多设备启动的标识
                .build();
        intent.setOperation(operation);
        ability.stopAbility(intent);
    }

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Service一旦创建就会一直保持在后台运行，除非必须回收内存资源，否则系统不会停止或销毁Service。开发者可以在Service中通过terminateAbility()停止本Service或在其他Ability调用stopAbility()来停止Service。

连接Service

如果Service需要与Page Ability或其他应用的Service Ability进行交互，则须创建用于连接的Connection。Service支持其他Ability通过connectAbility()方法与其进行连接。

在使用connectAbility()处理回调时，需要传入目标Service的Intent与IAbilityConnection的实例。IAbilityConnection提供了两个方法供开发者实现：onAbilityConnectDone()是用来处理连接Service成功的回调，onAbilityDisconnectDone()是用来处理Service异常死亡的回调。

// 创建连接Service回调实例
private IAbilityConnection connection = new IAbilityConnection() {
    // 连接到Service的回调
    @Override
    public void onAbilityConnectDone(ElementName elementName, IRemoteObject iRemoteObject, int resultCode) {
        // Client侧需要定义与Service侧相同的IRemoteObject实现类。开发者获取服务端传过来IRemoteObject对象，并从中解析出服务端传过来的信息。
    }

    // Service异常死亡的回调
    @Override
    public void onAbilityDisconnectDone(ElementName elementName, int resultCode) {
    }
};
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连接同一设备Service

连接service代码如下：

// 连接Service
Intent intent = new Intent();
Operation operation = new Intent.OperationBuilder()
        .withDeviceId("deviceId")
        .withBundleName("com.domainname.hiworld.himusic")
        .withAbilityName("com.domainname.hiworld.himusic.ServiceAbility")
        .build();
intent.setOperation(operation);
connectAbility(intent, connection);


	//这种方式也可以连接同一设备的service
    public void connectRemoteService() {
        Intent intent = new Intent();
        ElementName elementName = 
            new ElementName("", "com.example.remorerpcserver", "com.example.remorerpcserver.RemoteService");
        intent.setElement(elementName);
        ability.connectAbility(intent, this);
    }

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连接远程设备Service

// 连接Service
Intent intent = new Intent();
Operation operation = new Intent.OperationBuilder()
        .withDeviceId("deviceId")
        .withBundleName("com.domainname.hiworld.himusic")
        .withAbilityName("com.domainname.hiworld.himusic.ServiceAbility")
        .withFlags(Intent.FLAG_ABILITYSLICE_MULTI_DEVICE) // 设置支持分布式调度系统多设备启动的标识
        .build();
intent.setOperation(operation);
connectAbility(intent, connection);
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ServiceAbility生命周期

与PageAbility类似，Service也有生命周期，根据调用方法不同，其生命周期有以下两种路径：

• 启动Service

  该Service在其他Ability调用startAbility()时创建，然后保持运行。其他Ability通过调用stopAbility()来停止Service，Service停止后，系统会将其销毁。

• 连接Service

  该Service在其他Ability调用connectAbility()时创建，客户端可通过调用disconnectAbility()断开连接。多个客户端可以绑定到相同Service，而且当所有绑定全部取消后，系统即会销毁该Service。

前台Service

一般情况下，Service都是在后台运行的，后台Service的优先级都是比较低的，当资源不足时，系统有可能回收正在运行的后台Service。

在一些场景下（如播放音乐），用户希望应用能够一直保持运行，此时就需要使用前台Service。前台Service会始终保持正在运行的图标在系统状态栏显示。

使用前台Service并不复杂，开发者只需在Service创建的方法里，调用keepBackgroundRunning()将Service与通知绑定。调用keepBackgroundRunning()方法前需要在配置文件中声明ohos.permission.KEEP_BACKGROUND_RUNNING权限，同时还需要在配置文件中添加对应的backgroundModes参数。在onStop()方法中调用cancelBackgroundRunning()方法可停止前台Service。

使用前台Service的onStart()代码示例如下：

 @Override
    public void onStart(Intent intent) {
        HiLog.error(LABEL_LOG, "MyServiceAbility::onStart");
        startForeground();
        super.onStart(intent);
    }
    
	//创建前台服务
    private void startForeground(){
        // 创建通知，其中1005为notificationId
        NotificationRequest request = new NotificationRequest(NOTIFICATION_ID);
        NotificationRequest.NotificationNormalContent content = new NotificationRequest.NotificationNormalContent();
        content.setTitle("Foreground Service").setText("I'm a ForeGround Service");
        NotificationRequest.NotificationContent notificationContent = new NotificationRequest.NotificationContent(content);
        request.setContent(notificationContent);

        // 绑定通知，1005为创建通知时传入的notificationId
        keepBackgroundRunning(NOTIFICATION_ID, request);
    }

//取消前台服务
    private void cancelForeground(){
        cancelBackgroundRunning();
    }

    @Override
    public void onBackground() {
        super.onBackground();
        HiLog.error(LABEL_LOG, "MyServiceAbility::onBackground");
    }

    @Override
    public void onStop() {
        super.onStop();
        HiLog.error(LABEL_LOG, "MyServiceAbility::onStop");
        cancelForeground();
    }
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在配置文件中，“module > abilities”字段下对当前Service做如下配置：

{    
    "name": ".ServiceAbility",
    "type": "service",
    "visible": true,
    "backgroundModes": ["dataTransfer", "location"]
},
    "reqPermissions": [
      {
        "name": "ohos.permission.KEEP_BACKGROUND_RUNNING"
      }
    ]
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结尾

参考代码已上传github https://github.com/luncang/hmlearning