MainActivityWrapper.java revision 65fda1eaa94968bb55d5ded10dcb0b3f37fb05f2 
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
17package com.android.tv;
18
19import android.support.annotation.MainThread;
20import android.support.annotation.NonNull;
21import android.support.annotation.Nullable;
22import android.util.ArraySet;
23
24import com.android.tv.data.Channel;
25
26import java.util.Set;
27
28/**
29 * A wrapper for safely getting the current {@link MainActivity}.
30 * Note that this class is not thread-safe. All the public methods should be called on main thread.
31 */
32@MainThread
33public final class MainActivityWrapper {
34    private MainActivity mActivity;
35
36    private final Set<OnCurrentChannelChangeListener> mListeners = new ArraySet<>();
37
38    /**
39     * Returns the current main activity.
40     * <b>WARNING</b> do not keep a reference to MainActivity, leaking activities is expensive.
41     */
42    MainActivity getMainActivity() {
43        return mActivity;
44    }
45
46    /**
47     * Checks if the given {@code activity} is the current main activity.
48     */
49    boolean isCurrent(MainActivity activity) {
50        return activity != null && mActivity == activity;
51    }
52
53    /**
54     * Sets the currently created main activity instance.
55     */
56    public void onMainActivityCreated(@NonNull MainActivity activity) {
57        mActivity = activity;
58    }
59
60    /**
61     * Unsets the main activity instance.
62     */
63    public void onMainActivityDestroyed(@NonNull MainActivity activity) {
64        if (mActivity != activity) {
65            mActivity = null;
66        }
67    }
68
69    /**
70     * Notifies the current channel change.
71     */
72    void notifyCurrentChannelChange(@NonNull MainActivity caller, @Nullable Channel channel) {
73        if (mActivity == caller) {
74            for (OnCurrentChannelChangeListener listener : mListeners) {
75                listener.onCurrentChannelChange(channel);
76            }
77        }
78    }
79
80    /**
81     * Checks if the main activity is created.
82     */
83    public boolean isCreated() {
84        return mActivity != null;
85    }
86
87    /**
88     * Checks if the main activity is started.
89     */
90    public boolean isStarted() {
91        return mActivity != null && mActivity.isActivityStarted();
92    }
93
94    /**
95     * Checks if the main activity is resumed.
96     */
97    public boolean isResumed() {
98        return mActivity != null && mActivity.isActivityResumed();
99    }
100
101    /**
102     * Adds OnCurrentChannelChangeListener.
103     */
104    public void addOnCurrentChannelChangeListener(OnCurrentChannelChangeListener listener) {
105        mListeners.add(listener);
106    }
107
108    /**
109     * Removes OnCurrentChannelChangeListener.
110     */
111    public void removeOnCurrentChannelChangeListener(OnCurrentChannelChangeListener listener) {
112        mListeners.remove(listener);
113    }
114
115    /**
116     * Listener for the current channel change in main activity.
117     */
118    public interface OnCurrentChannelChangeListener {
119        /**
120         * Called when the current channel changes.
121         */
122        void onCurrentChannelChange(@Nullable Channel channel);
123    }
124}
125