Android studio 3.3.2-音乐播放器

package com.edu.sicnu.cs.zzy.mywork; import android.app.NotificationChannel; import android.app.NotificationManager; import android.app.PendingIntent; import android.app.Service; import android.content.ContentResolver; import android.content.Context; import android.content.Intent; import android.database.Cursor; import android.media.MediaPlayer; import android.os.IBinder; import android.provider.MediaStore; import android.support.v4.app.NotificationCompat; import android.text.TextUtils; import android.widget.RemoteViews; import java.io.IOException; import java.util.ArrayList; public class MusicService extends Service implements MediaPlayer.OnPreparedListener{ int current = -1; boolean isfirst; NotificationManager manager; RemoteViews mRemoteViews; NotificationCompat.Builder builder; ArrayList<Music> musiclist = new ArrayList<>(); static MediaPlayer mediaPlayer; final static String myChannel = "mymusicplayer"; public MusicService() { } @Override public IBinder onBind(Intent intent) { // TODO: Return the communication channel to the service. throw new UnsupportedOperationException("Not yet implemented"); } @Override public void onCreate() { super.onCreate(); mediaPlayer = new MediaPlayer(); mediaPlayer.setOnPreparedListener(this); getMusiclist(); //sendNotification(); //创建一个RemoteView实例 mRemoteViews = new RemoteViews(getPackageName(), R.layout.notification_window_layout); } @Override public int onStartCommand(Intent intent, int flags, int startId) { //由于每次都要先获取position,可能导致发送pause等命令时拿不到"position" int position = intent.getIntExtra("position",-1); if(position == -1){ //position为-1时代表没有接受到PlayerActivity发来的信息，说明 position= current; } if(position != current){ isfirst = true; } initRemoteView(); initNotification(); //第一次进入PlayerActivity时直接播放 if(isfirst){ isfirst = false; current = position; playNew(); }else { //之后可以接受其他命令 int operate = intent.getIntExtra("operate",-1); switch (operate){ case 0: goPlay(); break; case 1: play(); break; case 2: stop(); break; case 3: pause(); break; case 4: next(); break; case 5: prev(); break; } } String action = intent.getAction(); int intExtra = intent.getIntExtra("index",-1); //校验action if(TextUtils.equals(action, "ntf")){ switch (intExtra){ case 1: playNew(); break; case 4: next(); break; case 5: prev(); break; } } return super.onStartCommand(intent, flags, startId); } @Override public void onDestroy() { super.onDestroy(); mediaPlayer.release(); } // public void sendNotification(){ // NotificationManager manager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE); // // //判断安卓版本是否大于API-26 // if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) { // NotificationChannel channel = new NotificationChannel(myChannel,"my music notification", NotificationManager.IMPORTANCE_DEFAULT); // manager.createNotificationChannel(channel); // // builder = new NotificationCompat.Builder(this,myChannel); // builder.setSmallIcon(R.mipmap.ic_launcher).setContentTitle("MyMusicDemo:"); // // //设置延时意图，点击通知进入界面 // Intent intent = new Intent(this,MainActivity.class); // PendingIntent pendingIntent = PendingIntent.getActivity(this,0,intent,PendingIntent.FLAG_UPDATE_CURRENT); // builder.setContentIntent(pendingIntent); // startForeground(1,builder.build()); // } // } public void getMusiclist(){ ContentResolver resolver = getContentResolver(); Cursor cursor = resolver.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,null,null,null,null); while(cursor.moveToNext()){ String musicName = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE)); String musicPath = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA)); String musicArtist = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)); int duration = cursor.getInt(cursor.getColumnIndexOrThrow(MediaStore.Audio.Media.DURATION)); musiclist.add(new Music(musicName,musicPath,musicArtist,duration)); } } private void playNew() { try { mediaPlayer.reset(); mediaPlayer.setDataSource(musiclist.get(current).getMusicPath()); mediaPlayer.prepareAsync(); //异步调用，防止阻塞 mediaPlayer.setOnCompletionListener(new MediaPlayer.OnCompletionListener() { public void onCompletion(MediaPlayer arg0) { //如果当前歌曲播放完毕,自动播放下一首. next(); } }); } catch (IOException e) { e.printStackTrace(); } } private void play(){ playNew(); } private void stop(){ if(mediaPlayer.isPlaying()) mediaPlayer.stop(); } private void pause(){ if(mediaPlayer.isPlaying()) { mediaPlayer.pause(); } } //继续播放 public void goPlay(){ int position = getCurrentProgress(); mediaPlayer.seekTo(position);//设置当前MediaPlayer的播放位置，单位是毫秒。 try { mediaPlayer.prepare();// 同步的方式装载流媒体文件。 } catch (Exception e) { e.printStackTrace(); } mediaPlayer.start(); } // 获取当前进度 public static int getCurrentProgress() { if (mediaPlayer != null & mediaPlayer.isPlaying()) { return mediaPlayer.getCurrentPosition(); } else if (mediaPlayer != null & (!mediaPlayer.isPlaying())) { return mediaPlayer.getCurrentPosition(); } return 0; } private void next(){ current++; current = current % musiclist.size(); playNew(); } private void prev(){ current--; if(current<0) current = musiclist.size()-1; playNew(); } private void initRemoteView() { //实例化一个指向MusicService的intent Intent intent = new Intent(this, MusicService.class); intent.setAction("ntf"); //设置play按钮的点击事件 intent.putExtra("index", 1); PendingIntent pendingIntent_play = PendingIntent.getService(this, 1, intent, PendingIntent.FLAG_CANCEL_CURRENT); mRemoteViews.setOnClickPendingIntent(R.id.ntf_btn_play, pendingIntent_play); //设置next按钮的点击事件 intent.putExtra("index", 4); PendingIntent pendingIntent_next = PendingIntent.getService(this, 4, intent, Pendin