Refactor ActivityStatus to not store current activity

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

Index: base/android/java/src/org/chromium/base/ActivityStatus.java
diff --git a/base/android/java/src/org/chromium/base/ActivityStatus.java b/base/android/java/src/org/chromium/base/ActivityStatus.java
deleted file mode 100644
index df43dbebfbb9bf95df55fbb72607ecd9a1f85ff2..0000000000000000000000000000000000000000
--- a/base/android/java/src/org/chromium/base/ActivityStatus.java
+++ /dev/null
@@ -1,259 +0,0 @@
-// Copyright 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.app.Application;
-import android.app.Application.ActivityLifecycleCallbacks;
-import android.os.Bundle;
-
-import java.util.HashMap;
-import java.util.Map;
-
-/**
- * Provides information about the current activity's status, and a way
- * to register / unregister listeners for state changes.
- */
-@JNINamespace("base::android")
-public class ActivityStatus {
-
-    // Constants matching activity states reported to StateListener.onStateChange
-    // 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;
-
-    // Last activity that was shown (or null if none or it was destroyed).
-    private static Activity sActivity;
-
-    private static final Map<Activity, Integer> sActivityStates =
-            new HashMap<Activity, Integer>();
-
-    private static final ObserverList<StateListener> sStateListeners =
-            new ObserverList<StateListener>();
-
-    /**
-     * Interface to be implemented by listeners.
-     */
-    public interface StateListener {
-        /**
-         * Called when the activity's state changes.
-         * @param newState New activity state.
-         */
-        public void onActivityStateChange(int newState);
-    }
-
-    private ActivityStatus() {}
-
-    /**
-     * Initializes the activity status for a specified application.
-     *
-     * @param application The application whose status you wish to monitor.
-     */
-    public static void initialize(Application application) {
-        application.registerActivityLifecycleCallbacks(new ActivityLifecycleCallbacks() {
-            @Override
-            public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
-                onStateChange(activity, CREATED);
-            }
-
-            @Override
-            public void onActivityDestroyed(Activity activity) {
-                onStateChange(activity, DESTROYED);
-            }
-
-            @Override
-            public void onActivityPaused(Activity activity) {
-                onStateChange(activity, PAUSED);
-            }
-
-            @Override
-            public void onActivityResumed(Activity activity) {
-                onStateChange(activity, RESUMED);
-            }
-
-            @Override
-            public void onActivitySaveInstanceState(Activity activity, Bundle outState) {}
-
-            @Override
-            public void onActivityStarted(Activity activity) {
-                onStateChange(activity, STARTED);
-            }
-
-            @Override
-            public void onActivityStopped(Activity activity) {
-                onStateChange(activity, STOPPED);
-            }
-        });
-    }
-
-    /**
-     * Must be called by the main activity when it changes state.
-     *
-     * @param activity Current activity.
-     * @param newState New state value.
-     */
-    private static void onStateChange(Activity activity, int newState) {
-        if (activity == null) throw new IllegalArgumentException("null activity is not supported");
-
-        if (sActivity != activity) {
-            // ActivityStatus is notified with the CREATED event very late during the main activity
-            // creation to avoid making startup performance worse than it is by notifying observers
-            // that could do some expensive work. This can lead to non-CREATED events being fired
-            // before the CREATED event which is problematic.
-            // TODO(pliard): fix http://crbug.com/176837.
-            if (sActivity == null
-                    || newState == CREATED || newState == RESUMED || newState == STARTED) {
-                sActivity = activity;
-            }
-        }
-
-        if (newState != DESTROYED) {
-            sActivityStates.put(activity, newState);
-        } else {
-            sActivityStates.remove(activity);
-        }
-
-        if (sActivity == activity) {
-            for (StateListener listener : sStateListeners) {
-                listener.onActivityStateChange(newState);
-            }
-            if (newState == DESTROYED) {
-                sActivity = null;
-            }
-        }
-    }
-
-    /**
-     * Testing method to update the state of the specified activity.
-     */
-    public static void onStateChangeForTesting(Activity activity, int newState) {
-        onStateChange(activity, newState);
-    }
-
-    /**
-     * @return The current activity.
-     */
-    public static Activity getActivity() {
-        return sActivity;
-    }
-
-    /**
-     * @return The current activity's state (if no activity is registered, then DESTROYED will
-     *         be returned).
-     */
-    public static int getState() {
-        return getStateForActivity(sActivity);
-    }
-
-    /**
-     * Query the state for a given activity.  If the activity is not being tracked, this will
-     * return {@link #DESTROYED}.
-     *
-     * <p>
-     * When relying on this method, be familiar with the expected life cycle state
-     * transitions:
-     * <a href="http://developer.android.com/guide/components/activities.html#Lifecycle">
-     *   Activity Lifecycle
-     * </a>
-     *
-     * <p>
-     * During activity transitions (activity B launching in front of activity A), A will completely
-     * paused before the creation of activity B begins.
-     *
-     * <p>
-     * A basic flow for activity A starting, followed by activity B being opened and then closed:
-     * <ul>
-     *   <li> -- Starting Activity A --
-     *   <li> Activity A - CREATED
-     *   <li> Activity A - STARTED
-     *   <li> Activity A - RESUMED
-     *   <li> -- Starting Activity B --
-     *   <li> Activity A - PAUSED
-     *   <li> Activity B - CREATED
-     *   <li> Activity B - STARTED
-     *   <li> Activity B - RESUMED
-     *   <li> Activity A - STOPPED
-     *   <li> -- Closing Activity B, Activity A regaining focus --
-     *   <li> Activity B - PAUSED
-     *   <li> Activity A - STARTED
-     *   <li> Activity A - RESUMED
-     *   <li> Activity B - STOPPED
-     *   <li> Activity B - DESTROYED
-     * </ul>
-     *
-     * @param activity The activity whose state is to be returned.
-     * @return The state of the specified activity.
-     */
-    public static int getStateForActivity(Activity activity) {
-        Integer currentStatus = sActivityStates.get(activity);
-        return currentStatus != null ? currentStatus.intValue() : DESTROYED;
-    }
-
-    /**
-     * Registers the given listener to receive activity state changes.
-     * @param listener Listener to receive state changes.
-     */
-    public static void registerStateListener(StateListener listener) {
-        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() {
-        ThreadUtils.runOnUiThread(new Runnable () {
-            @Override
-            public void run() {
-                // 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);
-
-    /**
-     * Checks whether or not the Application's current Activity is visible to the user.  Note that
-     * this includes the PAUSED state, which can happen when the Activity is temporarily covered
-     * by another Activity's Fragment (e.g.).
-     * @return True if the Activity is visible, false otherwise.
-     */
-    public static boolean isApplicationVisible() {
-        int state = getState();
-        return state != STOPPED && state != DESTROYED;
-    }
-
-    /**
-     * Checks to see if there are any active Activity instances being watched by ActivityStatus.
-     * @return True if all Activities have been destroyed.
-     */
-    public static boolean isEveryActivityDestroyed() {
-        return sActivityStates.isEmpty();
-    }
-}