Add base/android/activity_status.cc

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.Handler;
 import android.os.Looper;
 
 /**
  * Provides information about the parent activity's status.
  */
+@JNINamespace("base::android")
 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;
+    // As an implementation detail, these are now defined in the auto-generated
+    // ActivityState interface, to be shared with C++.
+    public static final int CREATED = ActivityState.CREATED;
+    public static final int STARTED = ActivityState.STARTED;
+    public static final int RESUMED = ActivityState.RESUMED;
+    public static final int PAUSED = ActivityState.PAUSED;
+    public static final int STOPPED = ActivityState.STOPPED;
+    public static final int DESTROYED = ActivityState.DESTROYED;
 
     // 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;
 
     private static final ObserverList<StateListener> sStateListeners =
             new ObserverList<StateListener>();
@@ skipping 63 matching lines @@
         sStateListeners.addObserver(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) {
         sStateListeners.removeObserver(listener);
     }
+
+    /**
+     * Registers the single thread-safe native activity status listener.
+     * This handles the case where the caller is not on the main thread.
+     * Note that this is used by a leaky singleton object from the native
+     * side, hence lifecycle management is greatly simplified.
+     */
+    @CalledByNative
+    private static void registerThreadSafeNativeStateListener() {
+        Looper mainLooper = Looper.getMainLooper();
+        // If not on the main thread, post a Handler to perform the registration on it
+        // then return immediately. Note that registration will happen later.
+        if (Looper.myLooper() != mainLooper) {
+            new Handler(mainLooper).post(new Runnable() {
+                @Override
+                public void run() {
+                    // Note that this native method has to be static
+                    registerThreadSafeNativeStateListener();
+                }
+            });
+            return;
+        }
+
+        // Otherwise register a new listener that calls nativeOnActivityStateChange.
+        sStateListeners.addObserver(new StateListener() {
+            @Override
+            public void onActivityStateChange(int newState) {
+                nativeOnActivityStateChange(newState);
+            }
+        });
+    }
+
+    // Called to notify the native side of state changes.
+    // IMPORTANT: This is always called on the main thread!
+    private static native void nativeOnActivityStateChange(int newState);
 }