到这里音乐播放器该有的功能基本都有了，最后再添加一个通知栏控制功能——当我们后台运行的时候可以在通知栏看到我们的音乐播放状态并且可以控制音乐的暂停/播放/上一首/下一首；点击通知图标即可返回音乐播放器。要实现通知栏的显示功能需要用到Notification,他的视图是通过使用RemoteViews来实现的，Notification的显示和取消需要通过NotificationManager来控制。下面代码实现了通知栏的显示：
public class MainActivity extends Activity {......private NotificationManager nm;private RemoteViews contentViews;private Notification notify;private int NOTIFICATION_ID = 123;private boolean showNotification;......protected void onCreate(Bundle savedInstanceState) { ......initNotification();}private void initNotification() {//NotificationManager的获取nm = (NotificationManager)this.getSystemService(NOTIFICATION_SERVICE);Intent mainIntent = new Intent(MainActivity.this, MainActivity.class); PendingIntent pi = PendingIntent.getActivity(MainActivity.this, 0, mainIntent, 0);notify = new Notification();notify.when = System.currentTimeMillis();notify.icon = R.drawable.music;notify.contentIntent = pi;//点击通知跳转到MainActivitynotify.flags = Notification.FLAG_AUTO_CANCEL; contentViews = new RemoteViews(getPackageName(), R.layout.notification); contentViews.setOnClickPendingIntent(R.id.playtag, pi);contentViews.setOnClickPendingIntent(R.id.currentmusic, pi);//上一首图标添加点击监听Intent previousButtonIntent = new Intent(ACTION_PRE_SONG);PendingIntent pendPreviousButtonIntent = PendingIntent.getBroadcast(this, 0, previousButtonIntent, 0); contentViews.setOnClickPendingIntent(R.id.pre, pendPreviousButtonIntent);//播放/暂停添加点击监听Intent playPauseButtonIntent = new Intent(ACTION_PLAY_AND_PAUSE);PendingIntent playPausePendingIntent = PendingIntent.getBroadcast(this, 0, playPauseButtonIntent, 0); contentViews.setOnClickPendingIntent(R.id.playandpause, playPausePendingIntent);//下一首图标添加监听Intent nextButtonIntent = new Intent(ACTION_NEXT_SONG);PendingIntent pendNextButtonIntent = PendingIntent.getBroadcast(this, 0, nextButtonIntent, 0); contentViews.setOnClickPendingIntent(R.id.next, pendNextButtonIntent); //退出监听Intent exitButton = new Intent(ACTION_EXIT); PendingIntent pendingExitButtonIntent = PendingIntent.getBroadcast(this,0,exitButton,0); contentViews.setOnClickPendingIntent(R.id.close,pendingExitButtonIntent);}private void showNotification() {showNotification = true;if(isPlaying){ contentViews.setImageViewResource(R.id.playandpause,android.R.drawable.ic_media_pause); }else{contentViews.setImageViewResource(R.id.playandpause,android.R.drawable.ic_media_play); }contentViews.setTextViewText(R.id.currentmusic, currentMusicTitle + "—" + currentMusicArtist);String filePath = MainActivity.downloadedPath + "/album/"+ currentMusicTitle + "-" + currentMusicArtist + ".jpg";if (new File(filePath).exists()) {Bitmap bitmap = BitmapUtil.getScropBitmap(filePath, 60, 60);contentViews.setImageViewBitmap(R.id.playtag, bitmap);}notify.contentView = contentViews;nm.notify(NOTIFICATION_ID, notify);//调用notify方法后即可显示通知}private BroadcastReceiver playMusicReceiver = new BroadcastReceiver() {public void onReceive(Context context, Intent intent) {String action = intent.getAction();Log.d(TAG, "action = " + action);if (action.equals(ACTION_NEXT_SONG)) {nextSong();} else if (action.equals(ACTION_PLAY_SONG)) {playMusic(currentMusicPos);} else if (action.equals(ACTION_PAUSE)) {pauseMusic();} else if (action.equals(ACTION_PRE_SONG)) {preSong();} else if (action.equals(ACTION_CONTINUE_PLAYING_SONG)) {continuePlaying();} else if (action.equals(Intent.ACTION_CLOSE_SYSTEM_DIALOGS)) {//在播放器中点击home键时显示通知栏图标showNotification();} else if (action.equals(ACTION_EXIT)) {//通知栏点击退出图标finish();} else if (action.equals(ACTION_PLAY_AND_PAUSE)) {if (pause) {continuePlaying();pause = false;} else if (isPlaying) {pauseMusic();} else {playMusic(currentMusicPos);}}}};@Overrideprotected void onStart() {//回到音乐播放器时关闭通知if (showNotification) {nm.cancel(NOTIFICATION_ID);showNotification = false;}updatePlayMusicInfo();super.onStart();}Notification的显示和关闭主要是通过NotificationManager.notify()和NotificationManager.cancel()实现的。}
Notification的布局文件notification.xml如下：
<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="/apk/res/android"android:id="@+id/notification"android:layout_width="match_parent"android:layout_height="match_parent"android:orientation="horizontal"android:gravity="center_vertical"android:background="#65cb65"android:alpha="0.7"><!--android:background="#65cb65" --><ImageView android:id="@+id/playtag"android:layout_width="0dp"android:layout_height="60dp"android:layout_weight="1"android:src="@drawable/launcher"android:layout_marginLeft="5dp" /><TextView android:id="@+id/currentmusic"android:layout_width="0dp"android:layout_height="match_parent"android:layout_weight="3"android:layout_marginLeft="10dp"android:gravity="center_vertical"android:textSize="16dp"android:textColor="#f00"android:singleLine="true" android:ellipsize="marquee" android:marqueeRepeatLimit="marquee_forever"android:scrollHorizontally = "true" android:focusable ="true"android:focusableInTouchMode="true"/><ImageButton android:id="@+id/pre"android:layout_width="0dp"android:layout_height="wrap_content"android:src="@android:drawable/ic_media_previous"android:layout_weight="1" android:background="#dd00dd"/><ImageButton android:id="@+id/playandpause"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_marginLeft="10dp"android:layout_marginRight="10dp"android:layout_weight="1"android:background="#dd00dd"android:src="@android:drawable/ic_media_play" /><ImageButton android:id="@+id/next"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_marginRight="10dp"android:layout_weight="1"android:background="#dd00dd"android:src="@android:drawable/ic_media_next" /><ImageView android:id="@+id/close"android:layout_width="0dp"android:layout_height="wrap_content"android:layout_weight="1"android:src="@android:drawable/ic_delete" /></LinearLayout>
音乐播放器已完成，下载地址：
Android音乐播放器
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