Fire SystemMonitor::{RESUME,SUSPEND}_EVENT on Android.

base/android/java/src/org/chromium/base/ActivityStatus.java

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.base;
 
 import android.app.Activity;
 import android.os.Looper;
 
 import java.util.ArrayList;
 
 /**
  * Provides information about the parent activity's status.
  */
 public class ActivityStatus {
 
     // Constants matching activity states reported to StateListener.onStateChange
     public static final int CREATED = 1;
     public static final int STARTED = 2;
     public static final int RESUMED = 3;
     public static final int PAUSED = 4;
     public static final int STOPPED = 5;
     public static final int DESTROYED = 6;
 
-    // Current main activity, or null if none.
-    private static Activity sActivity;
-
-    // Current main activity's state. This can be set even if sActivity
-    // is null, to simplify unit testing.
     private static int sActivityState;
-
-    // Current activity instance, or null.
-    private static ActivityStatus sInstance;
-
-    // List of pause/resume listeners.
-    private final ArrayList<Listener> mListeners;
-
-    // List of state listeners.
-    private final ArrayList<StateListener> mStateListeners;
-
-    protected ActivityStatus() {
-        mListeners = new ArrayList<Listener>();
-        mStateListeners = new ArrayList<StateListener>();
-    }
-
-    /**
-     * Must be called by the main activity when it changes state.
-     * @param activity Current activity.
-     * @param newState New state value.
-     */
-    public static void onStateChange(Activity activity, int newState) {
-        if (newState == CREATED) {
-            sActivity = activity;
-        }
-        sActivityState = newState;
-        getInstance().changeState(newState);
-
-        if (newState == DESTROYED) {
-            sActivity = null;
-        }
-    }
-
-    private void changeState(int newState) {
-        for (StateListener listener : mStateListeners) {
-            listener.onActivityStateChange(newState);
-        }
-        if (newState == PAUSED || newState == RESUMED) {
-            boolean paused = (newState == PAUSED);
-            for (Listener listener : mListeners) {
-                listener.onActivityStatusChanged(paused);
-            }
-        }
-    }
-
-    // This interface can only be used to listen to PAUSED and RESUMED
-    // events. Deprecated, new code should use StateListener instead.
-    // TODO(digit): Remove once all users have switched to StateListener.
-    @Deprecated
-    public interface Listener {
-        /**
-         * Called when the activity is paused or resumed only.
-         * @param isPaused true if the activity is paused, false if not.
-         */
-        public void onActivityStatusChanged(boolean isPaused);
-    }
+    private static final ArrayList<StateListener> sStateListeners = new ArrayList<StateListener>();
 
     // Use this interface to listen to all state changes.
     public interface StateListener {
         /**
          * Called when the activity's state changes.
          * @param newState New activity state.
          */
-        public void onActivityStateChange(int newState);
+        public void onActivityStateChange(Activity activity, int newState);
     }
 
     /**
-     * Returns the current ActivityStatus instance.
+     * Must be called by the main activity when it changes state.
+     * @param activity Current activity.
+     * @param newState New state value.
      */
-    public static ActivityStatus getInstance() {
-        // Can only be called on the UI thread.
-        assert Looper.myLooper() == Looper.getMainLooper();
-        if (sInstance == null) {
-            sInstance = new ActivityStatus();
+    public static void onStateChange(Activity activity, int newState) {
+        sActivityState = newState;
+        for (StateListener listener : sStateListeners) {
+            listener.onActivityStateChange(activity, newState);
         }
-        return sInstance;
-    }
-
-    /**
-     * Indicates that the parent activity was paused.
-     */
-    public void onPause() {
-       changeState(PAUSED);
-    }
-
-    /**
-     * Indicates that the parent activity was resumed.
-     */
-    public void onResume() {
-        changeState(RESUMED);
     }
 
     /**
      * Indicates that the parent activity is currently paused.
      */
-    public boolean isPaused() {
+    public static boolean isPaused() {
         return sActivityState == PAUSED;
     }
 
     /**
-     * Returns the current main application activity.
-     */
-    public static Activity getActivity() {
-        return sActivity;
-    }
-
-    /**
      * Returns the current main application activity's state.
      */
     public static int getState() {
-        // To simplify unit testing, don't check sActivity for null.
         return sActivityState;
     }
 
     /**
-     * Registers the given pause/resume listener to receive activity
-     * status updates. Use registerStateListener() instead.
-     * @param listener Listener to receive status updates.
-     */
-    public void registerListener(Listener listener) {
-        mListeners.add(listener);
-    }
-
-    /**
-     * Unregisters the given pause/resume listener from receiving activity
-     * status updates. Use unregisterStateListener() instead.
-     * @param listener Listener that doesn't want to receive status updates.
-     */
-    public void unregisterListener(Listener listener) {
-        mListeners.remove(listener);
-    }
-
-    /**
      * Registers the given listener to receive activity state changes.
      * @param listener Listener to receive state changes.
      */
     public static void registerStateListener(StateListener listener) {
-        ActivityStatus status = getInstance();
-        status.mStateListeners.add(listener);
+        sStateListeners.add(listener);
     }
 
     /**
      * Unregisters the given listener from receiving activity state changes.
      * @param listener Listener that doesn't want to receive state changes.
      */
     public static void unregisterStateListener(StateListener listener) {
-        ActivityStatus status = getInstance();
-        status.mStateListeners.remove(listener);
+        sStateListeners.remove(listener);
     }
 }