Android: add support for headless js tasks

Summary: Provide a base `HeadlessJsTaskService` class that can be extended to run JS in headless mode in response to some event. Added `HeadlessJsTaskEventListener` for modules that are interested in background lifecycle events, and `HeadlessJsTaskContext` that basically extends `ReactContext` without touching it. The react instance is shared with the rest of the app (e.g. activities) through the `ReactNativeHost`.

Reviewed By: astreet

Differential Revision: D3225753

fbshipit-source-id: 2c5e7679636f31e0e7842d8a67aeb95baf47c563

ReactAndroid/src/main/java/com/facebook/react/BUCK

@@ -5,6 +5,7 @@ DEPS = [
   react_native_target('java/com/facebook/react/bridge:bridge'),
   react_native_target('java/com/facebook/react/common:common'),
   react_native_target('java/com/facebook/react/devsupport:devsupport'),
+  react_native_target('java/com/facebook/react/jstasks:jstasks'),
   react_native_target('java/com/facebook/react/module/annotations:annotations'),
   react_native_target('java/com/facebook/react/module/model:model'),
   react_native_target('java/com/facebook/react/modules/core:core'),

ReactAndroid/src/main/java/com/facebook/react/CoreModulesPackage.java

@@ -26,6 +26,7 @@ import com.facebook.react.devsupport.HMRClient;
 import com.facebook.react.devsupport.JSCHeapCapture;
 import com.facebook.react.devsupport.JSCSamplingProfiler;
 import com.facebook.react.module.annotations.ReactModuleList;
+import com.facebook.react.modules.core.HeadlessJsTaskSupportModule;
 import com.facebook.react.modules.core.DefaultHardwareBackBtnHandler;
 import com.facebook.react.modules.core.DeviceEventManagerModule;
 import com.facebook.react.modules.core.ExceptionsManagerModule;
@@ -97,6 +98,13 @@ import static com.facebook.react.bridge.ReactMarkerConstants.CREATE_UI_MANAGER_M
           return new AndroidInfoModule();
         }
       }));
+    moduleSpecList
+      .add(new ModuleSpec(HeadlessJsTaskSupportModule.class, new Provider<NativeModule>() {
+        @Override
+        public NativeModule get() {
+          return new HeadlessJsTaskSupportModule(reactContext);
+        }
+      }));
     moduleSpecList.add(
       new ModuleSpec(DeviceEventManagerModule.class, new Provider<NativeModule>() {
         @Override

ReactAndroid/src/main/java/com/facebook/react/HeadlessJsTaskService.java

@@ -0,0 +1,165 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react;
+
+import javax.annotation.Nullable;
+
+import java.util.Set;
+import java.util.concurrent.CopyOnWriteArraySet;
+
+import android.app.Service;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.os.IBinder;
+import android.os.PowerManager;
+
+import com.facebook.infer.annotation.Assertions;
+import com.facebook.react.bridge.ReactContext;
+import com.facebook.react.bridge.UiThreadUtil;
+import com.facebook.react.jstasks.HeadlessJsTaskEventListener;
+import com.facebook.react.jstasks.HeadlessJsTaskConfig;
+import com.facebook.react.jstasks.HeadlessJsTaskContext;
+
+/**
+ * Base class for running JS without a UI. Generally, you only need to override
+ * {@link #getTaskConfig}, which is called for every {@link #onStartCommand}. The
+ * result, if not {@code null}, is used to run a JS task.
+ *
+ * If you need more fine-grained control over how tasks are run, you can override
+ * {@link #onStartCommand} and call {@link #startTask} depending on your custom logic.
+ *
+ * If you're starting a {@code HeadlessJsTaskService} from a {@code BroadcastReceiver} (e.g.
+ * handling push notifications), make sure to call {@link #acquireWakeLockNow} before returning from
+ * {@link BroadcastReceiver#onReceive}, to make sure the device doesn't go to sleep before the
+ * service is started.
+ */
+public abstract class HeadlessJsTaskService extends Service implements HeadlessJsTaskEventListener {
+
+  private final Set<Integer> mActiveTasks = new CopyOnWriteArraySet<>();
+  private static @Nullable PowerManager.WakeLock sWakeLock;
+
+  @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;
+  }
+
+  /**
+   * Called from {@link #onStartCommand} to create a {@link HeadlessJsTaskConfig} for this intent.
+   * @param intent the {@link Intent} received in {@link #onStartCommand}.
+   * @return a {@link HeadlessJsTaskConfig} to be used with {@link #startTask}, or
+   *         {@code null} to ignore this command.
+   */
+  protected @Nullable HeadlessJsTaskConfig getTaskConfig(Intent intent) {
+    return null;
+  }
+
+  /**
+   * Acquire a wake lock to ensure the device doesn't go to sleep while processing background tasks.
+   */
+  public static void acquireWakeLockNow(Context context) {
+    if (sWakeLock == null || !sWakeLock.isHeld()) {
+      PowerManager powerManager =
+        Assertions.assertNotNull((PowerManager) context.getSystemService(POWER_SERVICE));
+      sWakeLock = powerManager.newWakeLock(
+        PowerManager.PARTIAL_WAKE_LOCK,
+        HeadlessJsTaskService.class.getSimpleName());
+      sWakeLock.setReferenceCounted(false);
+      sWakeLock.acquire();
+    }
+  }
+
+  @Override
+  public @Nullable IBinder onBind(Intent intent) {
+    return null;
+  }
+
+  /**
+   * Start a task. This method handles starting a new React instance if required.
+   *
+   * Has to be called on the UI thread.
+   *
+   * @param taskConfig describes what task to start and the parameters to pass to it
+   */
+  protected void startTask(final HeadlessJsTaskConfig taskConfig) {
+    UiThreadUtil.assertOnUiThread();
+    acquireWakeLockNow(this);
+    final ReactInstanceManager reactInstanceManager =
+      getReactNativeHost().getReactInstanceManager();
+    ReactContext reactContext = reactInstanceManager.getCurrentReactContext();
+    if (reactContext == null) {
+      reactInstanceManager
+        .addReactInstanceEventListener(new ReactInstanceManager.ReactInstanceEventListener() {
+          @Override
+          public void onReactContextInitialized(ReactContext reactContext) {
+            invokeStartTask(reactContext, taskConfig);
+            reactInstanceManager.removeReactInstanceEventListener(this);
+          }
+        });
+      if (!reactInstanceManager.hasStartedCreatingInitialContext()) {
+        reactInstanceManager.createReactContextInBackground();
+      }
+    } else {
+      invokeStartTask(reactContext, taskConfig);
+    }
+  }
+
+  private void invokeStartTask(ReactContext reactContext, HeadlessJsTaskConfig taskConfig) {
+    HeadlessJsTaskContext headlessJsTaskContext = HeadlessJsTaskContext.getInstance(reactContext);
+    headlessJsTaskContext.addTaskEventListener(this);
+    int taskId = headlessJsTaskContext.startTask(taskConfig);
+    mActiveTasks.add(taskId);
+  }
+
+  @Override
+  public void onDestroy() {
+    super.onDestroy();
+
+    if (getReactNativeHost().hasInstance()) {
+      ReactInstanceManager reactInstanceManager = getReactNativeHost().getReactInstanceManager();
+      ReactContext reactContext = reactInstanceManager.getCurrentReactContext();
+      if (reactContext != null) {
+        HeadlessJsTaskContext headlessJsTaskContext =
+          HeadlessJsTaskContext.getInstance(reactContext);
+        headlessJsTaskContext.removeTaskEventListener(this);
+      }
+    }
+    if (sWakeLock != null) {
+      sWakeLock.release();
+    }
+  }
+
+  @Override
+  public void onHeadlessJsTaskStart(int taskId) { }
+
+  @Override
+  public void onHeadlessJsTaskFinish(int taskId) {
+    mActiveTasks.remove(taskId);
+    if (mActiveTasks.size() == 0) {
+      stopSelf();
+    }
+  }
+
+  /**
+   * Get the {@link ReactNativeHost} used by this app. By default, assumes {@link #getApplication()}
+   * is an instance of {@link ReactApplication} and calls
+   * {@link ReactApplication#getReactNativeHost()}. Override this method if your application class
+   * does not implement {@code ReactApplication} or you simply have a different mechanism for
+   * storing a {@code ReactNativeHost}, e.g. as a static field somewhere.
+   */
+  protected ReactNativeHost getReactNativeHost() {
+    return ((ReactApplication) getApplication()).getReactNativeHost();
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/bridge/ReactContext.java

@@ -12,9 +12,9 @@ package com.facebook.react.bridge;
 import javax.annotation.Nullable;
 
 import java.lang.ref.WeakReference;
-import java.util.concurrent.CopyOnWriteArraySet;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.CopyOnWriteArraySet;
 
 import android.app.Activity;
 import android.content.Context;
@@ -47,6 +47,8 @@ public class ReactContext extends ContextWrapper {
   private final CopyOnWriteArraySet<ActivityEventListener> mActivityEventListeners =
       new CopyOnWriteArraySet<>();
 
+  private LifecycleState mLifecycleState = LifecycleState.BEFORE_CREATE;
+
   private @Nullable CatalystInstance mCatalystInstance;
   private @Nullable LayoutInflater mInflater;
   private @Nullable MessageQueueThread mUiMessageQueueThread;
@@ -54,7 +56,6 @@ public class ReactContext extends ContextWrapper {
   private @Nullable MessageQueueThread mJSMessageQueueThread;
   private @Nullable NativeModuleCallExceptionHandler mNativeModuleCallExceptionHandler;
   private @Nullable WeakReference<Activity> mCurrentActivity;
-  private LifecycleState mLifecycleState = LifecycleState.BEFORE_RESUME;
 
   public ReactContext(Context base) {
     super(base);
@@ -145,6 +146,10 @@ public class ReactContext extends ContextWrapper {
     return mCatalystInstance != null && !mCatalystInstance.isDestroyed();
   }
 
+  public LifecycleState getLifecycleState() {
+    return mLifecycleState;
+  }
+
   public void addLifecycleEventListener(final LifecycleEventListener listener) {
     mLifecycleEventListeners.add(listener);
     if (hasActiveCatalystInstance()) {
@@ -197,6 +202,7 @@ public class ReactContext extends ContextWrapper {
    */
   public void onHostResume(@Nullable Activity activity) {
     UiThreadUtil.assertOnUiThread();
+    mLifecycleState = LifecycleState.RESUMED;
     mCurrentActivity = new WeakReference(activity);
     mLifecycleState = LifecycleState.RESUMED;
     for (LifecycleEventListener listener : mLifecycleEventListeners) {
@@ -228,6 +234,7 @@ public class ReactContext extends ContextWrapper {
    */
   public void onHostDestroy() {
     UiThreadUtil.assertOnUiThread();
+    mLifecycleState = LifecycleState.BEFORE_CREATE;
     for (LifecycleEventListener listener : mLifecycleEventListeners) {
       listener.onHostDestroy();
     }

ReactAndroid/src/main/java/com/facebook/react/jstasks/BUCK

@@ -0,0 +1,23 @@
+include_defs('//ReactAndroid/DEFS')
+
+DEPS = [
+  react_native_target('java/com/facebook/react/bridge:bridge'),
+  react_native_target('java/com/facebook/react/common:common'),
+  react_native_target('java/com/facebook/react/uimanager:uimanager'),
+  react_native_dep('libraries/fbcore/src/main/java/com/facebook/common/logging:logging'),
+  react_native_dep('third-party/java/infer-annotations:infer-annotations'),
+  react_native_dep('third-party/java/jsr-305:jsr-305'),
+]
+
+android_library(
+  name = 'jstasks',
+  srcs = glob(['*.java']),
+  deps = DEPS,
+  visibility = [
+    'PUBLIC',
+  ],
+)
+
+project_config(
+  src_target = ':jstasks',
+)

ReactAndroid/src/main/java/com/facebook/react/jstasks/HeadlessJsTaskConfig.java

@@ -0,0 +1,76 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react.jstasks;
+
+import com.facebook.react.bridge.WritableMap;
+
+/**
+ * Class that holds the various parameters needed to start a JS task.
+ */
+public class HeadlessJsTaskConfig {
+  private final String mTaskKey;
+  private final WritableMap mData;
+  private final long mTimeout;
+  private final boolean mAllowedInForeground;
+
+  /**
+   * Create a HeadlessJsTaskConfig. Equivalent to calling
+   * {@link #HeadlessJsTaskConfig(String, WritableMap, long, boolean)} with no timeout (0) and
+   * {@code false} for {@code allowedInBackground}.
+   */
+  public HeadlessJsTaskConfig(String taskKey, WritableMap data) {
+    this(taskKey, data, 0, false);
+  }
+
+  /**
+   * Create a HeadlessJsTaskConfig. Equivalent to calling
+   * {@link #HeadlessJsTaskConfig(String, WritableMap, long, boolean)} with {@code false} for
+   * {@code allowedInBackground}.
+   */
+  public HeadlessJsTaskConfig(String taskKey, WritableMap data, long timeout) {
+    this(taskKey, data, timeout, false);
+  }
+
+  /**
+   * Create a HeadlessJsTaskConfig.
+   *
+   * @param taskKey the key for the JS task to execute. This is the same key that you call {@code
+   * AppRegistry.registerTask} with in JS.
+   * @param data a map of parameters passed to the JS task executor.
+   * @param timeout the amount of time (in ms) after which the React instance should be terminated
+   * regardless of whether the task has completed or not. This is meant as a safeguard against
+   * accidentally keeping the device awake for long periods of time because JS crashed or some
+   * request timed out. A value of 0 means no timeout (should only be used for long-running tasks
+   * such as music playback).
+   * @param allowedInForeground whether to allow this task to run while the app is in the foreground
+   * (i.e. there is a host in resumed mode for the current ReactContext). Only set this to true if
+   * you really need it. Note that tasks run in the same JS thread as UI code, so doing expensive
+   * operations would degrade user experience.
+   */
+  public HeadlessJsTaskConfig(
+    String taskKey,
+    WritableMap data,
+    long timeout,
+    boolean allowedInForeground) {
+    mTaskKey = taskKey;
+    mData = data;
+    mTimeout = timeout;
+    mAllowedInForeground = allowedInForeground;
+  }
+
+  /* package */ String getTaskKey() {
+    return mTaskKey;
+  }
+
+  /* package */ WritableMap getData() {
+    return mData;
+  }
+
+  /* package */ long getTimeout() {
+    return mTimeout;
+  }
+
+  /* package */ boolean isAllowedInForeground() {
+    return mAllowedInForeground;
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/jstasks/HeadlessJsTaskContext.java

@@ -0,0 +1,139 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+package com.facebook.react.jstasks;
+
+import java.util.Set;
+import java.util.WeakHashMap;
+import java.util.concurrent.CopyOnWriteArraySet;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import android.os.Handler;
+import android.util.SparseArray;
+
+import com.facebook.infer.annotation.Assertions;
+import com.facebook.react.bridge.ReactContext;
+import com.facebook.react.bridge.UiThreadUtil;
+import com.facebook.react.common.LifecycleState;
+import com.facebook.react.uimanager.AppRegistry;
+
+/**
+ * Helper class for dealing with JS tasks. Handles per-ReactContext active task tracking, starting /
+ * stopping tasks and notifying listeners.
+ */
+public class HeadlessJsTaskContext {
+
+  private static final WeakHashMap<ReactContext, HeadlessJsTaskContext> INSTANCES =
+    new WeakHashMap<>();
+
+  /**
+   * Get the task helper instance for a particular {@link ReactContext}. There is only one instance
+   * per context.
+   * <p>
+   * <strong>Note:</strong> do not hold long-lived references to the object returned here, as that
+   * will cause memory leaks. Instead, just call this method on-demand.
+   */
+  public static HeadlessJsTaskContext getInstance(ReactContext context) {
+    HeadlessJsTaskContext helper = INSTANCES.get(context);
+    if (helper == null) {
+      helper = new HeadlessJsTaskContext(context);
+      INSTANCES.put(context, helper);
+    }
+    return helper;
+  }
+
+  private final ReactContext mReactContext;
+  private final Set<HeadlessJsTaskEventListener> mHeadlessJsTaskEventListeners =
+    new CopyOnWriteArraySet<>();
+  private final AtomicInteger mLastTaskId = new AtomicInteger(0);
+  private final Handler mHandler = new Handler();
+  private final Set<Integer> mActiveTasks = new CopyOnWriteArraySet<>();
+  private final SparseArray<Runnable> mTaskTimeouts = new SparseArray<>();
+
+  private HeadlessJsTaskContext(ReactContext reactContext) {
+    mReactContext = reactContext;
+  }
+
+  /**
+   * Register a task lifecycle event listener.
+   */
+  public void addTaskEventListener(HeadlessJsTaskEventListener listener) {
+    mHeadlessJsTaskEventListeners.add(listener);
+  }
+
+  /**
+   * Unregister a task lifecycle event listener.
+   */
+  public void removeTaskEventListener(HeadlessJsTaskEventListener listener) {
+    mHeadlessJsTaskEventListeners.remove(listener);
+  }
+
+  /**
+   * Get whether there are any running JS tasks at the moment.
+   */
+  public boolean hasActiveTasks() {
+    return mActiveTasks.size() > 0;
+  }
+
+  /**
+   * Start a JS task. Handles invoking {@link AppRegistry#startHeadlessTask} and notifying
+   * listeners.
+   *
+   * @return a unique id representing this task instance.
+   */
+  public synchronized int startTask(final HeadlessJsTaskConfig taskConfig) {
+    UiThreadUtil.assertOnUiThread();
+    if (mReactContext.getLifecycleState() == LifecycleState.RESUMED &&
+      !taskConfig.isAllowedInForeground()) {
+      throw new IllegalStateException(
+        "Tried to start task " + taskConfig.getTaskKey() +
+          " while in foreground, but this is not allowed.");
+    }
+    final int taskId = mLastTaskId.incrementAndGet();
+    mReactContext.getJSModule(AppRegistry.class)
+      .startHeadlessTask(taskId, taskConfig.getTaskKey(), taskConfig.getData());
+    if (taskConfig.getTimeout() > 0) {
+      scheduleTaskTimeout(taskId, taskConfig.getTimeout());
+    }
+    mActiveTasks.add(taskId);
+    for (HeadlessJsTaskEventListener listener : mHeadlessJsTaskEventListeners) {
+      listener.onHeadlessJsTaskStart(taskId);
+    }
+    return taskId;
+  }
+
+  /**
+   * Finish a JS task. Doesn't actually stop the task on the JS side, only removes it from the list
+   * of active tasks and notifies listeners.
+   *
+   * @param taskId the unique id returned by {@link #startTask}.
+   */
+  public synchronized void finishTask(final int taskId) {
+    Assertions.assertCondition(
+      mActiveTasks.remove(taskId),
+      "Tried to finish non-existent task with id " + taskId + ".");
+    Runnable timeout = mTaskTimeouts.get(taskId);
+    if (timeout != null) {
+      mHandler.removeCallbacks(timeout);
+      mTaskTimeouts.remove(taskId);
+    }
+    UiThreadUtil.runOnUiThread(new Runnable() {
+      @Override
+      public void run() {
+        for (HeadlessJsTaskEventListener listener : mHeadlessJsTaskEventListeners) {
+          listener.onHeadlessJsTaskFinish(taskId);
+        }
+      }
+    });
+  }
+
+  private void scheduleTaskTimeout(final int taskId, long timeout) {
+    Runnable runnable = new Runnable() {
+      @Override
+      public void run() {
+        finishTask(taskId);
+      }
+    };
+    mTaskTimeouts.append(taskId, runnable);
+    mHandler.postDelayed(runnable, timeout);
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/jstasks/HeadlessJsTaskEventListener.java

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.jstasks;
+
+/**
+ * Listener interface for task lifecycle events.
+ */
+public interface HeadlessJsTaskEventListener {
+
+  /**
+   * Called when a JS task is started, on the UI thread.
+   *
+   * @param taskId the unique identifier of this task instance
+   */
+  void onHeadlessJsTaskStart(int taskId);
+
+  /**
+   * Called when a JS task finishes (i.e. when
+   * {@link HeadlessJsTaskSupportModule#notifyTaskFinished} is called, or when it times out), on the
+   * UI thread.
+   */
+  void onHeadlessJsTaskFinish(int taskId);
+}

ReactAndroid/src/main/java/com/facebook/react/modules/core/BUCK

@@ -12,6 +12,7 @@ android_library(
     react_native_target('java/com/facebook/react/devsupport:devsupport'),
     react_native_target('java/com/facebook/react/module/annotations:annotations'),
     react_native_target('java/com/facebook/react/uimanager:uimanager'),
+    react_native_target('java/com/facebook/react/jstasks:jstasks'),
   ],
   visibility = [
     'PUBLIC',

ReactAndroid/src/main/java/com/facebook/react/modules/core/HeadlessJsTaskSupportModule.java

@@ -0,0 +1,38 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.modules.core;
+
+import com.facebook.react.bridge.ReactApplicationContext;
+import com.facebook.react.bridge.ReactContextBaseJavaModule;
+import com.facebook.react.bridge.ReactMethod;
+import com.facebook.react.jstasks.HeadlessJsTaskContext;
+
+/**
+ * Simple native module that allows JS to notify native of having completed some task work, so that
+ * it can e.g. release any resources, stop timers etc.
+ */
+public class HeadlessJsTaskSupportModule extends ReactContextBaseJavaModule {
+
+  public HeadlessJsTaskSupportModule(ReactApplicationContext reactContext) {
+    super(reactContext);
+  }
+
+  @Override
+  public String getName() {
+    return "HeadlessJsTaskSupport";
+  }
+
+  @ReactMethod
+  public void notifyTaskFinished(int taskId) {
+    HeadlessJsTaskContext headlessJsTaskContext =
+      HeadlessJsTaskContext.getInstance(getReactApplicationContext());
+    headlessJsTaskContext.finishTask(taskId);
+  }
+}

ReactAndroid/src/main/java/com/facebook/react/modules/core/Timing.java

@@ -9,6 +9,18 @@
 
 package com.facebook.react.modules.core;
 
+import javax.annotation.Nullable;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.PriorityQueue;
+import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
+
 import android.util.SparseArray;
 import android.view.Choreographer;
 
@@ -24,27 +36,17 @@ import com.facebook.react.bridge.UiThreadUtil;
 import com.facebook.react.bridge.WritableArray;
 import com.facebook.react.common.SystemClock;
 import com.facebook.react.devsupport.DevSupportManager;
+import com.facebook.react.jstasks.HeadlessJsTaskEventListener;
+import com.facebook.react.jstasks.HeadlessJsTaskContext;
 import com.facebook.react.module.annotations.ReactModule;
 import com.facebook.react.uimanager.ReactChoreographer;
 
-import java.util.ArrayList;
-import java.util.Comparator;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.PriorityQueue;
-import java.util.Set;
-import java.util.concurrent.atomic.AtomicBoolean;
-
-import javax.annotation.Nullable;
-
 /**
  * Native module for JS timer execution. Timers fire on frame boundaries.
  */
 @ReactModule(name = "RCTTiming", supportsWebWorkers = true)
 public final class Timing extends ReactContextBaseJavaModule implements LifecycleEventListener,
-  OnExecutorUnregisteredListener {
+  OnExecutorUnregisteredListener, HeadlessJsTaskEventListener {
 
   // These timing contants should be kept in sync with the ones in `JSTimersExecution.js`.
   // The minimum time in milliseconds left in the frame to call idle callbacks.
@@ -88,7 +90,7 @@ public final class Timing extends ReactContextBaseJavaModule implements Lifecycl
      */
     @Override
     public void doFrame(long frameTimeNanos) {
-      if (isPaused.get()) {
+      if (isPaused.get() && !isRunningTasks.get()) {
         return;
       }
 
@@ -132,7 +134,7 @@ public final class Timing extends ReactContextBaseJavaModule implements Lifecycl
 
     @Override
     public void doFrame(long frameTimeNanos) {
-      if (isPaused.get()) {
+      if (isPaused.get() && !isRunningTasks.get()) {
         return;
       }
 
@@ -197,6 +199,7 @@ public final class Timing extends ReactContextBaseJavaModule implements Lifecycl
   private final PriorityQueue<Timer> mTimers;
   private final Map<ExecutorToken, SparseArray<Timer>> mTimerIdsToTimers;
   private final AtomicBoolean isPaused = new AtomicBoolean(true);
+  private final AtomicBoolean isRunningTasks = new AtomicBoolean(false);
   private final TimerFrameCallback mTimerFrameCallback = new TimerFrameCallback();
   private final IdleFrameCallback mIdleFrameCallback = new IdleFrameCallback();
   private @Nullable IdleCallbackRunnable mCurrentIdleCallbackRunnable;
@@ -236,19 +239,22 @@ public final class Timing extends ReactContextBaseJavaModule implements Lifecycl
     // Safe to acquire choreographer here, as initialize() is invoked from UI thread.
     mReactChoreographer = ReactChoreographer.getInstance();
     getReactApplicationContext().addLifecycleEventListener(this);
+    HeadlessJsTaskContext headlessJsTaskContext =
+      HeadlessJsTaskContext.getInstance(getReactApplicationContext());
+    headlessJsTaskContext.addTaskEventListener(this);
   }
 
   @Override
   public void onHostPause() {
     isPaused.set(true);
     clearChoreographerCallback();
-    clearChoreographerIdleCallback();
+    maybeClearChoreographerIdleCallback();
   }
 
   @Override
   public void onHostDestroy() {
     clearChoreographerCallback();
-    clearChoreographerIdleCallback();
+    maybeClearChoreographerIdleCallback();
   }
 
   @Override
@@ -257,11 +263,25 @@ public final class Timing extends ReactContextBaseJavaModule implements Lifecycl
     // TODO(5195192) Investigate possible problems related to restarting all tasks at the same
     // moment
     setChoreographerCallback();
+    maybeSetChoreographerIdleCallback();
+  }
 
-    synchronized (mIdleCallbackGuard) {
-      if (mSendIdleEventsExecutorTokens.size() > 0) {
-        setChoreographerIdleCallback();
-      }
+  @Override
+  public void onHeadlessJsTaskStart(int taskId) {
+    if (!isRunningTasks.getAndSet(true)) {
+      setChoreographerCallback();
+      maybeSetChoreographerIdleCallback();
+    }
+  }
+
+  @Override
+  public void onHeadlessJsTaskFinish(int taskId) {
+    HeadlessJsTaskContext headlessJsTaskContext =
+      HeadlessJsTaskContext.getInstance(getReactApplicationContext());
+    if (!headlessJsTaskContext.hasActiveTasks()) {
+      isRunningTasks.set(false);
+      clearChoreographerCallback();
+      maybeClearChoreographerIdleCallback();
     }
   }
 
@@ -269,6 +289,23 @@ public final class Timing extends ReactContextBaseJavaModule implements Lifecycl
   public void onCatalystInstanceDestroy() {
     clearChoreographerCallback();
     clearChoreographerIdleCallback();
+    HeadlessJsTaskContext headlessJsTaskContext =
+      HeadlessJsTaskContext.getInstance(getReactApplicationContext());
+    headlessJsTaskContext.removeTaskEventListener(this);
+  }
+
+  private void maybeSetChoreographerIdleCallback() {
+    synchronized (mIdleCallbackGuard) {
+      if (mSendIdleEventsExecutorTokens.size() > 0) {
+        setChoreographerIdleCallback();
+      }
+    }
+  }
+
+  private void maybeClearChoreographerIdleCallback() {
+    if (isPaused.get() && !isRunningTasks.get()) {
+      clearChoreographerCallback();
+    }
   }
 
   private void setChoreographerCallback() {
@@ -281,7 +318,10 @@ public final class Timing extends ReactContextBaseJavaModule implements Lifecycl
   }
 
   private void clearChoreographerCallback() {
-    if (mFrameCallbackPosted) {
+    HeadlessJsTaskContext headlessJsTaskContext =
+      HeadlessJsTaskContext.getInstance(getReactApplicationContext());
+    if (mFrameCallbackPosted && isPaused.get() &&
+      !headlessJsTaskContext.hasActiveTasks()) {
       Assertions.assertNotNull(mReactChoreographer).removeFrameCallback(
           ReactChoreographer.CallbackType.TIMERS_EVENTS,
           mTimerFrameCallback);

ReactAndroid/src/main/java/com/facebook/react/uimanager/AppRegistry.java

@@ -19,5 +19,5 @@ public interface AppRegistry extends JavaScriptModule {
 
   void runApplication(String appKey, WritableMap appParameters);
   void unmountApplicationComponentAtRootTag(int rootNodeTag);
-
+  void startHeadlessTask(int taskId, String taskKey, WritableMap data);
 }