MainActivityWrapper.java revision 2e1279b8bbe0603fb4399b25b73121bed5953c46 
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.support.annotation.UiThread;
23import android.util.ArraySet;
24
25import com.android.tv.data.Channel;
26
27import 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
34public 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