我正在尝试制作一个简单的服务来播放mp3文件。下面是我的服务类代码。
public class MyService extends Service {
private IBinder iBinder = new LocalBinder();
private ArrayList<Song> songsList;
private MediaPlayer player;
@Override
public void onCreate() {
player = new MediaPlayer();
player.setAudioStreamType(AudioManager.STREAM_MUSIC);
player.reset();
}
@Override
public IBinder onBind(Intent intent) {
return iBinder;
}
public class LocalBinder extends Binder{
public MyService getService() {
return MyService.this;
}
}
public void setSongsList(ArrayList<Song> songsList) {
this.songsList = songsList;
}
public void playSong(Song song) {
try {
player.setDataSource(getApplicationContext(), Uri.parse(song.getPath()));
player.prepare();
player.start();
} catch (IOException e) {
e.printStackTrace();
}
}
}
这是我的Activity类。
public class MyActivity extends Activity {
private MyService myService;
private boolean mBound;
private ArrayList<Song> songsList = new ArrayList<Song>();
private Uri musicUri;
private ContentResolver musicResolver;
private int count;
ServiceConnection serviceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
mBound = true;
MyService.LocalBinder binder = (MyService.LocalBinder)iBinder;
myService = binder.getService();
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
mBound = false;
//myService = null;
}
};
@Override
protected void onStart() {
super.onStart();
Intent i = new Intent(this, MyService.class);
bindService(i, serviceConnection, BIND_AUTO_CREATE);
}
@Override
protected void onStop() {
super.onStop();
if(mBound) {
myService.unbindService(serviceConnection);
mBound = false;
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
musicResolver = getContentResolver();
prepareListOfSongsAndAlbumMap();
/*for(Song s: songsList) {
Log.i("Song", s.getTitle());
}*/
if(myService == null) {
Log.i("NULL SERVICE", "NULL");
}
myService.setSongsList(songsList);
myService.playSong(songsList.get(3));
}
private void prepareListOfSongsAndAlbumMap() {
this.musicUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
String[] projection = null;
String sortOrder = MediaStore.Audio.Media.TITLE + " ASC";
String selectionMimeType = MediaStore.Audio.Media.IS_MUSIC + " !=0";
Cursor musicCursor = musicResolver.query(musicUri, projection, selectionMimeType, null, sortOrder);
count = musicCursor.getCount();
if(musicCursor != null && musicCursor.moveToFirst()) {
do {
String path = musicCursor.getString(musicCursor.getColumnIndex(MediaStore.Audio.Media.DATA));
String title = musicCursor.getString(musicCursor.getColumnIndex(MediaStore.Audio.Media.TITLE));
String album = musicCursor.getString(musicCursor.getColumnIndex(MediaStore.Audio.Media.ALBUM));
String artist = musicCursor.getString(musicCursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));
int artistId = musicCursor.getInt(musicCursor.getColumnIndex(MediaStore.Audio.Media.ARTIST_ID));
int albumId = musicCursor.getInt(musicCursor.getColumnIndex(MediaStore.Audio.Media.ALBUM_ID));
int trackId = musicCursor.getInt(musicCursor.getColumnIndex(MediaStore.Audio.Media.TRACK));
long duration = musicCursor.getInt(musicCursor.getColumnIndex(MediaStore.Audio.Media.DURATION));
Uri sArtworkUri = Uri
.parse("content://media/external/audio/albumart");
Uri albumArtUri = ContentUris.withAppendedId(sArtworkUri, albumId);
Song song = new Song(path, title, album, artist, albumId, trackId, duration, albumArtUri.toString(), artistId);
songsList.add(song);
}while(musicCursor.moveToNext());
}
musicCursor.close();
}
}
当我尝试运行此代码时，我收到NullPointerException，myService未被创建。我无法弄清楚我在哪里弄错了。
以下是日志详细信息。
java.lang.RuntimeException: Unable to start activity ComponentInfo{music.skumar.com.servicetest/music.skumar.com.servicetest.MyActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2218)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2268)
at android.app.ActivityThread.access$600(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1263)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5162)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
atcom.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:756)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:572)
at miui.dexspy.DexspyInstaller.main(DexspyInstaller.java:171)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at music.skumar.com.servicetest.MyActivity.onCreate(MyActivity.java:76)
at android.app.Activity.performCreate(Activity.java:5135)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
at com.lbe.security.service.core.client.b.x.callActivityOnCreate(Unknown Source)
atandroid.app.ActivityThread.performLaunchActivity(ActivityThread.java:2182) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2268)
at android.app.ActivityThread.access$600(ActivityThread.java:148)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1263)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5162)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:525)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:756)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:572)
at miui.dexspy.DexspyInstaller.main(DexspyInstaller.java:171)
at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：1)
myService中的null将为onCreate()。您不仅要在bindService()之前调用onStart()（在onCreate()之后发生），而且bindService()是异步的。在调用myService之前，请勿尝试使用onServiceConnected()。