我正在尝试创建一个能在Android后台播放音乐的服务 但是在服务开始时我得到了NPE 谁能告诉我我做错了什么？
Log cat：
12-28 12:07:19.602: W/System.err(3768): java.lang.IllegalStateException
12-28 12:07:19.722: W/System.err(3768): at android.media.MediaPlayer.prepare(Native Method)
12-28 12:07:19.722: W/System.err(3768): at com.darkovski.quran.myPlayService.playMedia(myPlayService.java:413)
12-28 12:07:19.722: W/System.err(3768): at com.darkovski.quran.myPlayService.onPrepared(myPlayService.java:390)
12-28 12:07:19.722: W/System.err(3768): at android.media.MediaPlayer$EventHandler.handleMessage(MediaPlayer.java:1523)
12-28 12:07:19.722: W/System.err(3768): at android.os.Handler.dispatchMessage(Handler.java:99)
12-28 12:07:19.722: W/System.err(3768): at android.os.Looper.loop(Looper.java:137)
12-28 12:07:19.722: W/System.err(3768): at android.app.ActivityThread.main(ActivityThread.java:4441)
12-28 12:07:19.722: W/System.err(3768): at java.lang.reflect.Method.invokeNative(Native Method)
12-28 12:07:19.722: W/System.err(3768): at java.lang.reflect.Method.invoke(Method.java:511)
12-28 12:07:19.722: W/System.err(3768): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-28 12:07:19.722: W/System.err(3768): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-28 12:07:19.722: W/System.err(3768): at dalvik.system.NativeStart.main(Native Method)
我的代码：
public class myPlayService extends Service implements OnCompletionListener,
OnPreparedListener, OnErrorListener, OnSeekCompleteListener,
OnInfoListener, OnBufferingUpdateListener {
private static final String TAG = "TELSERVICE";
private MediaPlayer mediaPlayer = new MediaPlayer();
// songs
private ArrayList<Songs> songs;
private int position;
// Set up the notification ID
private static final int NOTIFICATION_ID = 1;
private boolean isPausedInCall = false;
private PhoneStateListener phoneStateListener;
private TelephonyManager telephonyManager;
// ---Variables for seekbar processing---
String sntSeekPos;
int intSeekPos;
int mediaPosition;
int mediaMax;
// Intent intent;
private final Handler handler = new Handler();
private static int songEnded;
public static final String BROADCAST_ACTION = "com.darkovski.quran.seekprogress";
// Set up broadcast identifier and intent
public static final String BROADCAST_BUFFER = "com.darkovski.quran.broadcastbuffer";
Intent bufferIntent;
Intent seekIntent;
// Declare headsetSwitch variable
private int headsetSwitch = 1;
// OnCreate
@Override
public void onCreate() {
Log.v(TAG, "Creating Service");
// android.os.Debug.waitForDebugger();
// Instantiate bufferIntent to communicate with Activity for progress
// dialogue
songs = new ArrayList<Songs>();
bufferIntent = new Intent(BROADCAST_BUFFER);
// ---Set up intent for seekbar broadcast ---
seekIntent = new Intent(BROADCAST_ACTION);
mediaPlayer.setOnCompletionListener(this);
mediaPlayer.setOnErrorListener(this);
mediaPlayer.setOnPreparedListener(this);
mediaPlayer.setOnBufferingUpdateListener(this);
mediaPlayer.setOnSeekCompleteListener(this);
mediaPlayer.setOnInfoListener(this);
mediaPlayer.reset();
// Register headset receiver
registerReceiver(headsetReceiver, new IntentFilter(
Intent.ACTION_HEADSET_PLUG));
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
// get songs and position
songs = (ArrayList<Songs>) intent.getSerializableExtra("songs");
position = intent.getIntExtra("position", -1);
try {
mediaPlayer.setDataSource(songs.get(position).getLink());
} catch (IllegalArgumentException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (SecurityException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IllegalStateException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
// ---Set up receiver for seekbar change ---
registerReceiver(broadcastReceiver, new IntentFilter(
Player.BROADCAST_SEEKBAR));
// Manage incoming phone calls during playback. Pause mp on incoming,
// resume on hangup.
// -----------------------------------------------------------------------------------
// Get the telephony manager
Log.v(TAG, "Starting telephony");
telephonyManager = (TelephonyManager) getSystemService(Context.TELEPHONY_SERVICE);
Log.v(TAG, "Starting listener");
phoneStateListener = new PhoneStateListener() {
@Override
public void onCallStateChanged(int state, String incomingNumber) {
// String stateString = "N/A";
Log.v(TAG, "Starting CallStateChange");
switch (state) {
case TelephonyManager.CALL_STATE_OFFHOOK:
case TelephonyManager.CALL_STATE_RINGING:
if (mediaPlayer != null) {
pauseMedia();
isPausedInCall = true;
}
break;
case TelephonyManager.CALL_STATE_IDLE:
// Phone idle. Start playing.
if (mediaPlayer != null) {
if (isPausedInCall) {
isPausedInCall = false;
playMedia();
}
}
break;
}
}
};
// Register the listener with the telephony manager
telephonyManager.listen(phoneStateListener,
PhoneStateListener.LISTEN_CALL_STATE);
// Insert notification start
initNotification();
mediaPlayer.reset();
// Set up the MediaPlayer data source using the strAudioLink value
if (!mediaPlayer.isPlaying()) {
try {
// Send message to Activity to display progress dialogue
sendBufferingBroadcast();
mediaPlayer.setDataSource(songs.get(position).getLink());
;
// Prepare mediaplayer
mediaPlayer.prepare();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalStateException e) {
e.printStackTrace();
} catch (IOException e) {
}
}
// --- Set up seekbar handler ---
setupHandler();
return START_STICKY;
}
// ---Send seekbar info to activity----
private void setupHandler() {
handler.removeCallbacks(sendUpdatesToUI);
handler.postDelayed(sendUpdatesToUI, 1000); // 1 second
}
private Runnable sendUpdatesToUI = new Runnable() {
public void run() {
// // Log.d(TAG, "entered sendUpdatesToUI");
LogMediaPosition();
handler.postDelayed(this, 1000); // 2 seconds
}
};
private void LogMediaPosition() {
// // Log.d(TAG, "entered LogMediaPosition");
if (mediaPlayer.isPlaying()) {
mediaPosition = mediaPlayer.getCurrentPosition();
// if (mediaPosition < 1) {
// Toast.makeText(this, "Buffering...", Toast.LENGTH_SHORT).show();
// }
mediaMax = mediaPlayer.getDuration();
// seekIntent.putExtra("time", new Date().toLocaleString());
seekIntent.putExtra("counter", String.valueOf(mediaPosition));
seekIntent.putExtra("mediamax", String.valueOf(mediaMax));
seekIntent.putExtra("song_ended", String.valueOf(songEnded));
sendBroadcast(seekIntent);
}
}
// --Receive seekbar position if it has been changed by the user in the
// activity
private BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
updateSeekPos(intent);
}
};
// Update seek position from Activity
public void updateSeekPos(Intent intent) {
int seekPos = intent.getIntExtra("seekpos", 0);
if (mediaPlayer.isPlaying()) {
handler.removeCallbacks(sendUpdatesToUI);
mediaPlayer.seekTo(seekPos);
setupHandler();
}
}
// ---End of seekbar code
// If headset gets unplugged, stop music and service.
private BroadcastReceiver headsetReceiver = new BroadcastReceiver() {
private boolean headsetConnected = false;
@Override
public void onReceive(Context context, Intent intent) {
// TODO Auto-generated method stub
// Log.v(TAG, "ACTION_HEADSET_PLUG Intent received");
if (intent.hasExtra("state")) {
if (headsetConnected && intent.getIntExtra("state", 0) == 0) {
headsetConnected = false;
headsetSwitch = 0;
// Log.v(TAG, "State = Headset disconnected");
// headsetDisconnected();
} else if (!headsetConnected
&& intent.getIntExtra("state", 0) == 1) {
headsetConnected = true;
headsetSwitch = 1;
// Log.v(TAG, "State = Headset connected");
}
}
switch (headsetSwitch) {
case (0):
headsetDisconnected();
break;
case (1):
break;
}
}
};
private void headsetDisconnected() {
stopMedia();
stopSelf();
}
// --- onDestroy, stop media player and release. Also stop
// phoneStateListener, notification, receivers...---
@Override
public void onDestroy() {
super.onDestroy();
if (mediaPlayer != null) {
if (mediaPlayer.isPlaying()) {
mediaPlayer.stop();
}
mediaPlayer.release();
}
if (phoneStateListener != null) {
telephonyManager.listen(phoneStateListener,
PhoneStateListener.LISTEN_NONE);
}
// Cancel the notification
cancelNotification();
// Unregister headsetReceiver
unregisterReceiver(headsetReceiver);
// Unregister seekbar receiver
unregisterReceiver(broadcastReceiver);
// Stop the seekbar handler from sending updates to UI
handler.removeCallbacks(sendUpdatesToUI);
// Service ends, need to tell activity to display "Play" button
resetButtonPlayStopBroadcast();
}
// Send a message to Activity that audio is being prepared and buffering
// started.
private void sendBufferingBroadcast() {
// Log.v(TAG, "BufferStartedSent");
bufferIntent.putExtra("buffering", "1");
sendBroadcast(bufferIntent);
}
// Send a message to Activity that audio is prepared and ready to start
// playing.
private void sendBufferCompleteBroadcast() {
// Log.v(TAG, "BufferCompleteSent");
bufferIntent.putExtra("buffering", "0");
sendBroadcast(bufferIntent);
}
// Send a message to Activity to reset the play button.
private void resetButtonPlayStopBroadcast() {
// Log.v(TAG, "BufferCompleteSent");
bufferIntent.putExtra("buffering", "2");
sendBroadcast(bufferIntent);
}
@Override
public void onBufferingUpdate(MediaPlayer arg0, int arg1) {
// TODO Auto-generated method stub
}
@Override
public boolean onInfo(MediaPlayer arg0, int arg1, int arg2) {
// TODO Auto-generated method stub
return false;
}
@Override
public void onSeekComplete(MediaPlayer mp) {
if (!mediaPlayer.isPlaying()) {
playMedia();
Toast.makeText(this, "SeekComplete", Toast.LENGTH_SHORT).show();
}
}
// ---Error processing ---
@Override
public boolean onError(MediaPlayer mp, int what, int extra) {
switch (what) {
case MediaPlayer.MEDIA_ERROR_NOT_VALID_FOR_PROGRESSIVE_PLAYBACK:
Toast.makeText(this,
"MEDIA ERROR NOT VALID FOR PROGRESSIVE PLAYBACK " + extra,
Toast.LENGTH_SHORT).show();
break;
case MediaPlayer.MEDIA_ERROR_SERVER_DIED:
Toast.makeText(this, "MEDIA ERROR SERVER DIED " + extra,
Toast.LENGTH_SHORT).show();
break;
case MediaPlayer.MEDIA_ERROR_UNKNOWN:
Toast.makeText(this, "MEDIA ERROR UNKNOWN " + extra,
Toast.LENGTH_SHORT).show();
break;
}
return false;
}
@Override
public void onPrepared(MediaPlayer arg0) {
// Send a message to activity to end progress dialogue
sendBufferCompleteBroadcast();
playMedia();
}
@Override
public void onCompletion(MediaPlayer mp) {
// When song ends, need to tell activity to display "Play" button
position += 1;
stopMedia();
playMedia();
// stopSelf();
}
@Override
public IBinder onBind(Intent arg0) {
// TODO Auto-generated method stub
return null;
}
public void playMedia() {
if (!mediaPlayer.isPlaying()) {
try {
//line 413
mediaPlayer.prepare();
} catch (IllegalStateException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
// Add for Telephony Manager
public void pauseMedia() {
// Log.v(TAG, "Pause Media");
if (mediaPlayer.isPlaying()) {
mediaPlayer.pause();
}
}
public void stopMedia() {
if (mediaPlayer.isPlaying()) {
mediaPlayer.stop();
}
mediaPlayer.release();
}
// Create Notification
private void initNotification() {
String ns = Context.NOTIFICATION_SERVICE;
NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);
int icon = R.drawable.ic_launcher;
CharSequence tickerText = "Tutorial: Music In Service";
long when = System.currentTimeMillis();
Notification notification = new Notification(icon, tickerText, when);
notification.flags = Notification.FLAG_ONGOING_EVENT;
Context context = getApplicationContext();
CharSequence contentTitle = "Music In Service App Tutorial";
CharSequence contentText = "Listen To Music While Performing Other Tasks";
Intent notificationIntent = new Intent(this, Player.class);
PendingIntent contentIntent = PendingIntent.getActivity(context, 0,
notificationIntent, 0);
notification.setLatestEventInfo(context, contentTitle, contentText,
contentIntent);
mNotificationManager.notify(NOTIFICATION_ID, notification);
}
// Cancel Notification
private void cancelNotification() {
String ns = Context.NOTIFICATION_SERVICE;
NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns);
mNotificationManager.cancel(NOTIFICATION_ID);
}
}
谁能告诉我我做错了什么？
答案 0 :(得分：0)
首先，这不是NPE（空指针异常）。
其次，您经常过于频繁地调用playMedia方法。考虑到它调用MediaPlayer.prepare，它在我看到它被调用的几个地方没有意义。特别是，您在onPrepared回调中调用它。 MediaPlayer的状态机正在为您提供IllegalStateException，因为您无法从准备好的状态调用prepare。您也不应该从prepare回调中拨打onCompletion。 MediaPlayer有一个严格的state machine，您应该更加关注它。