Java tutorial
/* * Copyright (C) 2014 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.lzhang.stockchartt.media; import android.app.PendingIntent; import android.content.Context; import android.content.Intent; import android.os.Bundle; import android.os.Handler; import android.os.Message; import android.os.RemoteException; import android.support.annotation.NonNull; import android.support.v4.media.MediaBrowserCompat.MediaItem; import android.support.v4.media.MediaBrowserServiceCompat; import android.support.v4.media.MediaMetadataCompat; import android.support.v4.media.session.MediaButtonReceiver; import android.support.v4.media.session.MediaSessionCompat; import android.support.v4.media.session.PlaybackStateCompat; import com.example.lzhang.stockchartt.R; import com.example.lzhang.stockchartt.media.model.MusicProvider; import com.example.lzhang.stockchartt.media.playback.LocalPlayback; import com.example.lzhang.stockchartt.media.playback.PlaybackManager; import com.example.lzhang.stockchartt.media.playback.QueueManager; import com.example.lzhang.stockchartt.media.ui.MusicPlayerActivity; import com.example.lzhang.stockchartt.media.utils.LogHelper; import com.example.lzhang.stockchartt.media.utils.MusicProviderV2; import java.lang.ref.WeakReference; import java.util.ArrayList; import java.util.List; import static com.example.lzhang.stockchartt.media.utils.MediaIDHelper.MEDIA_ID_EMPTY_ROOT; import static com.example.lzhang.stockchartt.media.utils.MediaIDHelper.MEDIA_ID_ROOT; /** * This class provides a MediaBrowser through a service. It exposes the media library to a browsing * client, through the onGetRoot and onLoadChildren methods. It also creates a MediaSession and * exposes it through its MediaSession.Token, which allows the client to create a MediaController * that connects to and send control commands to the MediaSession remotely. This is useful for * user interfaces that need to interact with your media session, like Android Auto. You can * (should) also use the same service from your app's UI, which gives a seamless playback * experience to the user. * * To implement a MediaBrowserService, you need to: * * <ul> * * <li> Extend {@link android.service.media.MediaBrowserService}, implementing the media browsing * related methods {@link android.service.media.MediaBrowserService#onGetRoot} and * {@link android.service.media.MediaBrowserService#onLoadChildren}; * <li> In onCreate, start a new {@link android.media.session.MediaSession} and notify its parent * with the session's token {@link android.service.media.MediaBrowserService#setSessionToken}; * * <li> Set a callback on the * {@link android.media.session.MediaSession#setCallback(android.media.session.MediaSession.Callback)}. * The callback will receive all the user's actions, like play, pause, etc; * * <li> Handle all the actual music playing using any method your app prefers (for example, * {@link android.media.MediaPlayer}) * * <li> Update playbackState, "now playing" metadata and queue, using MediaSession proper methods * {@link android.media.session.MediaSession#setPlaybackState(android.media.session.PlaybackState)} * {@link android.media.session.MediaSession#setMetadata(android.media.MediaMetadata)} and * {@link android.media.session.MediaSession#setQueue(java.util.List)}) * * <li> Declare and export the service in AndroidManifest with an intent receiver for the action * android.media.browse.MediaBrowserService * * </ul> * * To make your app compatible with Android Auto, you also need to: * * <ul> * * <li> Declare a meta-data tag in AndroidManifest.xml linking to a xml resource * with a <automotiveApp> root element. For a media app, this must include * an <uses name="media"/> element as a child. * For example, in AndroidManifest.xml: * <meta-data android:name="com.google.android.gms.car.application" * android:resource="@xml/automotive_app_desc"/> * And in res/values/automotive_app_desc.xml: * <automotiveApp> * <uses name="media"/> * </automotiveApp> * * </ul> * @see <a href="README.md">README.md</a> for more details. * */ public class MusicService extends MediaBrowserServiceCompat implements PlaybackManager.PlaybackServiceCallback { private static final String TAG = "zhanglei";//LogHelper.makeLogTag(MusicService.class); // Extra on MediaSession that contains the Cast device name currently connected to public static final String EXTRA_CONNECTED_CAST = "com.example.android.uamp.CAST_NAME"; // The action of the incoming Intent indicating that it contains a command // to be executed (see {@link #onStartCommand}) public static final String ACTION_CMD = "com.example.android.uamp.ACTION_CMD"; // The key in the extras of the incoming Intent indicating the command that // should be executed (see {@link #onStartCommand}) public static final String CMD_NAME = "CMD_NAME"; // A value of a CMD_NAME key in the extras of the incoming Intent that // indicates that the music playback should be paused (see {@link #onStartCommand}) public static final String CMD_PAUSE = "CMD_PAUSE"; // A value of a CMD_NAME key that indicates that the music playback should switch // to local playback from cast playback. public static final String CMD_STOP_CASTING = "CMD_STOP_CASTING"; // Delay stopSelf by using a handler. private static final int STOP_DELAY = 30000; private MusicProvider mMusicProvider; private PlaybackManager mPlaybackManager; private MediaSessionCompat mSession; private MediaNotificationManager mMediaNotificationManager; private Bundle mSessionExtras; private final DelayedStopHandler mDelayedStopHandler = new DelayedStopHandler(this); private PackageValidator mPackageValidator; /* * (non-Javadoc) * @see android.app.Service#onCreate() */ @Override public void onCreate() { super.onCreate(); LogHelper.d(TAG, "onCreate"); mMusicProvider = new MusicProvider(); // To make the app more responsive, fetch and cache catalog information now. // This can help improve the response time in the method // {@link #onLoadChildren(String, Result<List<MediaItem>>) onLoadChildren()}. // mMusicProvider.retrieveMediaAsync(null /* Callback */); mPackageValidator = new PackageValidator(this); QueueManager queueManager = new QueueManager(mMusicProvider, getResources(), new QueueManager.MetadataUpdateListener() { @Override public void onMetadataChanged(MediaMetadataCompat metadata) { mSession.setMetadata(metadata); } @Override public void onMetadataRetrieveError() { mPlaybackManager.updatePlaybackState(getString(R.string.error_no_metadata)); } @Override public void onCurrentQueueIndexUpdated(int queueIndex) { mPlaybackManager.handlePlayRequest(); } @Override public void onQueueUpdated(String title, List<MediaSessionCompat.QueueItem> newQueue) { mSession.setQueue(newQueue); mSession.setQueueTitle(title); } }); LocalPlayback playback = new LocalPlayback(this, mMusicProvider); mPlaybackManager = new PlaybackManager(this, getResources(), mMusicProvider, queueManager, playback); // Start a new MediaSession mSession = new MediaSessionCompat(this, "MusicService"); setSessionToken(mSession.getSessionToken()); mSession.setCallback(mPlaybackManager.getMediaSessionCallback()); mSession.setFlags( MediaSessionCompat.FLAG_HANDLES_MEDIA_BUTTONS | MediaSessionCompat.FLAG_HANDLES_TRANSPORT_CONTROLS); Context context = getApplicationContext(); Intent intent = new Intent(context, MusicPlayerActivity.class); PendingIntent pi = PendingIntent.getActivity(context, 99 /*request code*/, intent, PendingIntent.FLAG_UPDATE_CURRENT); mSession.setSessionActivity(pi); mSessionExtras = new Bundle(); mSession.setExtras(mSessionExtras); mPlaybackManager.updatePlaybackState(null); try { mMediaNotificationManager = new MediaNotificationManager(this); } catch (RemoteException e) { throw new IllegalStateException("Could not create a MediaNotificationManager", e); } } /** * (non-Javadoc) * @see android.app.Service#onStartCommand(android.content.Intent, int, int) */ @Override public int onStartCommand(Intent startIntent, int flags, int startId) { if (startIntent != null) { String action = startIntent.getAction(); String command = startIntent.getStringExtra(CMD_NAME); if (ACTION_CMD.equals(action)) { if (CMD_PAUSE.equals(command)) { mPlaybackManager.handlePauseRequest(); } else if (CMD_STOP_CASTING.equals(command)) { // CastContext.getSharedInstance(this).getSessionManager().endCurrentSession(true); } } else { // Try to handle the intent as a media button event wrapped by MediaButtonReceiver MediaButtonReceiver.handleIntent(mSession, startIntent); } } // Reset the delay handler to enqueue a message to stop the service if // nothing is playing. mDelayedStopHandler.removeCallbacksAndMessages(null); mDelayedStopHandler.sendEmptyMessageDelayed(0, STOP_DELAY); return START_STICKY; } /** * (non-Javadoc) * @see android.app.Service#onDestroy() */ @Override public void onDestroy() { LogHelper.d(TAG, "onDestroy"); // Service is being killed, so make sure we release our resources mPlaybackManager.handleStopRequest(null); mMediaNotificationManager.stopNotification(); mDelayedStopHandler.removeCallbacksAndMessages(null); mSession.release(); } @Override public BrowserRoot onGetRoot(@NonNull String clientPackageName, int clientUid, Bundle rootHints) { LogHelper.d(TAG, "OnGetRoot: clientPackageName=" + clientPackageName, "; clientUid=" + clientUid + " ; rootHints=", rootHints); // To ensure you are not allowing any arbitrary app to browse your app's contents, you // need to check the origin: if (!mPackageValidator.isCallerAllowed(this, clientPackageName, clientUid)) { // If the request comes from an untrusted package, return an empty browser root. // If you return null, then the media browser will not be able to connect and // no further calls will be made to other media browsing methods. LogHelper.i(TAG, "OnGetRoot: Browsing NOT ALLOWED for unknown caller. " + "Returning empty browser root so all apps can use MediaController." + clientPackageName); // return new MediaBrowserServiceCompat.BrowserRoot(MEDIA_ID_EMPTY_ROOT, null); } return new BrowserRoot(MEDIA_ID_ROOT, null); } @Override public void onLoadChildren(@NonNull final String parentMediaId, @NonNull final Result<List<MediaItem>> result) { LogHelper.d(TAG, "OnLoadChildren: parentMediaId=", parentMediaId); if (MEDIA_ID_EMPTY_ROOT.equals(parentMediaId)) { result.sendResult(new ArrayList<MediaItem>()); } else if (mMusicProvider.isInitialized()) { // if music library is ready, return immediately // result.sendResult(mMusicProvider.getChildren(parentMediaId, getResources())); result.sendResult(MusicProviderV2.getInstance().mMusicItemList); } else { // otherwise, only return results when the music library is retrieved result.detach(); mMusicProvider.retrieveMediaAsync(new MusicProvider.Callback() { @Override public void onMusicCatalogReady(boolean success) { result.sendResult(mMusicProvider.getChildren(parentMediaId, getResources())); } }); } } /** * Callback method called from PlaybackManager whenever the music is about to play. */ @Override public void onPlaybackStart() { mSession.setActive(true); mDelayedStopHandler.removeCallbacksAndMessages(null); // The service needs to continue running even after the bound client (usually a // MediaController) disconnects, otherwise the music playback will stop. // Calling startService(Intent) will keep the service running until it is explicitly killed. startService(new Intent(getApplicationContext(), MusicService.class)); } /** * Callback method called from PlaybackManager whenever the music stops playing. */ @Override public void onPlaybackStop() { mSession.setActive(false); // Reset the delayed stop handler, so after STOP_DELAY it will be executed again, // potentially stopping the service. mDelayedStopHandler.removeCallbacksAndMessages(null); mDelayedStopHandler.sendEmptyMessageDelayed(0, STOP_DELAY); stopForeground(true); } @Override public void onNotificationRequired() { mMediaNotificationManager.startNotification(); } @Override public void onPlaybackStateUpdated(PlaybackStateCompat newState) { mSession.setPlaybackState(newState); } /** * A simple handler that stops the service if playback is not active (playing) */ private static class DelayedStopHandler extends Handler { private final WeakReference<MusicService> mWeakReference; private DelayedStopHandler(MusicService service) { mWeakReference = new WeakReference<>(service); } @Override public void handleMessage(Message msg) { MusicService service = mWeakReference.get(); if (service != null && service.mPlaybackManager.getPlayback() != null) { if (service.mPlaybackManager.getPlayback().isPlaying()) { LogHelper.d(TAG, "Ignoring delayed stop since the media player is in use."); return; } LogHelper.d(TAG, "Stopping service with delay handler."); service.stopSelf(); } } } }