HeadlessJsTaskService

在没有UI的情况下运行JS代码。通常，你只需要重写#getTaskConfig方法，每个#onStartCommand都会调用此方法。结果（除了null之外）都会被用到JS任务中。

如果您需要对任务的运行方式更细粒度的控制，你可以重写#onStartCommand并取决于您的自定义逻辑来调用#startTask

如果您是从BroadcastReceiver启动的HeadlessJsTaskService(例如处理推送通知)，请确保在从BroadcastReceiver#onReceive返回之前先调用#acquireWakeLockNow，以确保在启动服务之前设备不会进入睡眠状态。

onStartCommand

  @Override
  public int onStartCommand(Intent intent, int flags, int startId) {
    HeadlessJsTaskConfig taskConfig = getTaskConfig(intent);
    if (taskConfig != null) {
      startTask(taskConfig);
      return START_REDELIVER_INTENT;
    }
    return START_NOT_STICKY;
  }

getTaskConfig

在#onStartCommand内调用此方法来创建一个HeadlessJsTaskConfig

• @param Intent 详见#acquireWakeLockNow
• @return 和#startTask一起使用的HeadlessJsTaskConfig或者null(@Nullable)

import java.util.concurrent.TimeUnit;

public class MyService extends HeadlessJsTaskService {
  @Override
  protected @Nullable HeadlessJsTaskConfig getTaskConfig(Intent intent) {
    Bundle extras = intent.getExtras();
    // If extras have been passed to the intent, pass them on into the JS as taskData
    // which can be accessed as the first param.
    WritableMap data = /* extras != null ? Arguments.fromBundle(extras) : */ Arguments.createMap();

    int timeout = extras.getInt("timeout",5);

    return new HeadlessJsTaskConfig(
        // The the task was registered with in JS - must match
        "BackgroundTask",
        data,
        TimeUnit.SECONDS.toMillis(timeout)
    )

  }
}

acquireWakeLockNow

Context context = getContext().getApplicationContext();
Intent service = new Intent(context, MyService.class);
service.putExtra("time", 5)
context.startService(service);

HeadlessJsTaskService.acquireWakeLockNow(context);

onBind

@Override
public IBinder onBind(Intent intent) {
  // TODO: Return the communication channel to the service.
  throw new UnsupportedOperationException("Not yet implemented");
}

startTask

启动任务。如果需要，此方法将处理启动新的React实例。 必须在UI线程上调用。

• @param taskConfig描述来要启动的任务以及要传递给它的参数

protected void startTask(final HeadlessJsTaskConfig taskConfig) {
  //...
  invokeStartTask(reactContext, taskConfig);
}

invokeStartTask

private void invokeStartTask(ReactContext reactContext, final HeadlessJsTaskConfig taskConfig) {
   UiThreadUtil.runOnUiThread(
      new Runnable() {
        @Override
        public void run() {
          int taskId = headlessJsTaskContext.startTask(taskConfig);
          mActiveTasks.add(taskId);
        }
      }
    );
}

onDestroy

onHeadlessJsTaskStart

onHeadlessJsTaskFinish

getReactNativeHost