android: Improve ActivityStatus and add ChromiumActivity.

The ActivityStatus class used to track activity state changes is too basic
for some usage scenarios.

This patch does the following:

- Augment ActivityStatus with a new StateListener type that can be
  registered to listen to all activity state changes.

  Also add getActivity(), getState(), registerStateListener()
  and unregisterStateListener() as static method.

- Add a new ChromiumActivity class that all Chromium main activities
  should sub-class, to ensure that the ActivityStatus state is updated
  appropriately.

- Modify all main activities in the Chromium code base to extend
  from ChromiumActivity instead of Activity.

BUG=none


Review URL: https://chromiumcodereview.appspot.com/11419287

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171789 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 166 insertions, 20 deletions

diff --git a/base/android/java/src/org/chromium/base/ActivityStatus.java b/base/android/java/src/org/chromium/base/ActivityStatus.java
index 765d841..b80c149 100644
--- a/base/android/java/src/org/chromium/base/ActivityStatus.java
+++ b/base/android/java/src/org/chromium/base/ActivityStatus.java
@@ -4,6 +4,7 @@
 
 package org.chromium.base;
 
+import android.app.Activity;
 import android.os.Looper;
 
 import java.util.ArrayList;
@@ -12,55 +13,137 @@ 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's status changes.
+         * 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 boolean mIsPaused = false;
-    private ArrayList<Listener> mListeners = new ArrayList<Listener>();
-    private static ActivityStatus sActivityStatus;
-
-    private ActivityStatus() {
+    // 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);
     }
 
+    /**
+     * Returns the current ActivityStatus instance.
+     */
     public static ActivityStatus getInstance() {
         // Can only be called on the UI thread.
         assert Looper.myLooper() == Looper.getMainLooper();
-        if (sActivityStatus == null) {
-            sActivityStatus = new ActivityStatus();
+        if (sInstance == null) {
+            sInstance = new ActivityStatus();
         }
-        return sActivityStatus;
+        return sInstance;
     }
 
     /**
      * Indicates that the parent activity was paused.
      */
     public void onPause() {
-        mIsPaused = true;
-        informAllListeners();
+       changeState(PAUSED);
     }
 
     /**
      * Indicates that the parent activity was resumed.
      */
     public void onResume() {
-        mIsPaused = false;
-        informAllListeners();
+        changeState(RESUMED);
     }
 
     /**
      * Indicates that the parent activity is currently paused.
      */
     public boolean isPaused() {
-        return mIsPaused;
+        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 listener to receive activity status updates.
+     * 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) {
@@ -68,16 +151,29 @@ public class ActivityStatus {
     }
 
     /**
-     * Unregisters the given listener from receiving activity status updates.
+     * 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);
     }
 
-    private void informAllListeners() {
-        for (Listener listener : mListeners) {
-            listener.onActivityStatusChanged(mIsPaused);
-        }
+    /**
+     * 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);
+    }
+
+    /**
+     * 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);
     }
 }
diff --git a/base/android/java/src/org/chromium/base/ChromiumActivity.java b/base/android/java/src/org/chromium/base/ChromiumActivity.java
new file mode 100644
index 0000000..f857e12
--- /dev/null
+++ b/base/android/java/src/org/chromium/base/ChromiumActivity.java
@@ -0,0 +1,50 @@
+// 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.Bundle;
+
+// All Chromium main activities should extend this class.
+// This allows various sub-systems to properly react to activity
+// state changes.
+public class ChromiumActivity extends Activity {
+
+  @Override
+  protected void onCreate(Bundle savedInstance) {
+    super.onCreate(savedInstance);
+    ActivityStatus.onStateChange(this, ActivityStatus.CREATED);
+  }
+
+  @Override
+  protected void onStart() {
+    super.onStart();
+    ActivityStatus.onStateChange(this, ActivityStatus.STARTED);
+  }
+
+  @Override
+  protected void onResume() {
+    super.onResume();
+    ActivityStatus.onStateChange(this, ActivityStatus.STARTED);
+  }
+
+  @Override
+  protected void onPause() {
+    ActivityStatus.onStateChange(this, ActivityStatus.STARTED);
+    super.onPause();
+  }
+
+  @Override
+  protected void onStop() {
+    ActivityStatus.onStateChange(this, ActivityStatus.STARTED);
+    super.onStop();
+  }
+
+  @Override
+  protected void onDestroy() {
+    ActivityStatus.onStateChange(this, ActivityStatus.DESTROYED);
+    super.onDestroy();
+  }
+}