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      1 /*
      2  * Copyright (C) 2015 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.tv;
     18 
     19 import android.support.annotation.MainThread;
     20 import android.support.annotation.NonNull;
     21 import android.support.annotation.Nullable;
     22 import android.support.annotation.UiThread;
     23 import android.util.ArraySet;
     24 
     25 import com.android.tv.data.Channel;
     26 
     27 import java.util.Set;
     28 
     29 /**
     30  * A wrapper for safely getting the current {@link MainActivity}.
     31  * Note that this class is not thread-safe. All the public methods should be called on main thread.
     32  */
     33 @MainThread
     34 public final class MainActivityWrapper {
     35     private MainActivity mActivity;
     36 
     37     private final Set<OnCurrentChannelChangeListener> mListeners = new ArraySet<>();
     38 
     39     /**
     40      * Returns the current main activity.
     41      * <b>WARNING</b> do not keep a reference to MainActivity, leaking activities is expensive.
     42      */
     43     MainActivity getMainActivity() {
     44         return mActivity;
     45     }
     46 
     47     /**
     48      * Checks if the given {@code activity} is the current main activity.
     49      */
     50     boolean isCurrent(MainActivity activity) {
     51         return activity != null && mActivity == activity;
     52     }
     53 
     54     /**
     55      * Sets the currently created main activity instance.
     56      */
     57     @UiThread
     58     public void onMainActivityCreated(@NonNull MainActivity activity) {
     59         mActivity = activity;
     60     }
     61 
     62     /**
     63      * Unsets the main activity instance.
     64      */
     65     @UiThread
     66     public void onMainActivityDestroyed(@NonNull MainActivity activity) {
     67         if (mActivity != activity) {
     68             mActivity = null;
     69         }
     70     }
     71 
     72     /**
     73      * Notifies the current channel change.
     74      */
     75     void notifyCurrentChannelChange(@NonNull MainActivity caller, @Nullable Channel channel) {
     76         if (mActivity == caller) {
     77             for (OnCurrentChannelChangeListener listener : mListeners) {
     78                 listener.onCurrentChannelChange(channel);
     79             }
     80         }
     81     }
     82 
     83     /**
     84      * Checks if the main activity is created.
     85      */
     86     public boolean isCreated() {
     87         return mActivity != null;
     88     }
     89 
     90     /**
     91      * Checks if the main activity is started.
     92      */
     93     public boolean isStarted() {
     94         return mActivity != null && mActivity.isActivityStarted();
     95     }
     96 
     97     /**
     98      * Checks if the main activity is resumed.
     99      */
    100     public boolean isResumed() {
    101         return mActivity != null && mActivity.isActivityResumed();
    102     }
    103 
    104     /**
    105      * Adds OnCurrentChannelChangeListener.
    106      */
    107     @UiThread
    108     public void addOnCurrentChannelChangeListener(OnCurrentChannelChangeListener listener) {
    109         mListeners.add(listener);
    110     }
    111 
    112     /**
    113      * Removes OnCurrentChannelChangeListener.
    114      */
    115     @UiThread
    116     public void removeOnCurrentChannelChangeListener(OnCurrentChannelChangeListener listener) {
    117         mListeners.remove(listener);
    118     }
    119 
    120     /**
    121      * Listener for the current channel change in main activity.
    122      */
    123     public interface OnCurrentChannelChangeListener {
    124         /**
    125          * Called when the current channel changes.
    126          */
    127         void onCurrentChannelChange(@Nullable Channel channel);
    128     }
    129 }
    130