服务在onCreate上使用nullpointerexception崩溃
我想检查服务中每5分钟的实际时间，并根据时间静音或取消静音。 早些时候我试图在最后使用一段时间（true）和thread.sleep（300000），但它总是用ANR崩溃，所以我试图使用一个计时器任务，但现在它在线AudioManager audioManager = (AudioManager)this.getSystemService(Context.AUDIO_SERVICE);之后崩溃了AudioManager audioManager = (AudioManager)this.getSystemService(Context.AUDIO_SERVICE); 使用NullPointerException
package de.nathan.android.droidschool; import android.app.Service; import android.content.Context; import android.content.Intent; import android.media.AudioManager; import android.os.IBinder; import java.io.File; import java.util.GregorianCalendar; import java.util.Timer; import java.util.TimerTask; /** * Created by nathan on 29.08.13. */ public class MuteService extends Service { Timer myTimer = new Timer(); MyTimerTask myTimerTask= new MyTimerTask(); AudioManager audioManager = (AudioManager)this.getSystemService(Context.AUDIO_SERVICE); public void onCreate() { super.onCreate(); } public int onStartCommand(Intent intent, int i1, int i2) { super.onStartCommand(intent, i1, i2); myTimer.scheduleAtFixedRate(myTimerTask, 0, 600000); //(timertask,delay,period) return START_STICKY; } public MuteService() { } @Override public IBinder onBind(Intent intent) { return null; } private class MyTimerTask extends TimerTask { @Override public void run() { GregorianCalendar cal = new GregorianCalendar(); String tag = null; switch (cal.get(GregorianCalendar.DAY_OF_WEEK)) { case GregorianCalendar.MONDAY: tag = "Montag"; break; case GregorianCalendar.TUESDAY: tag = "Dienstag"; break; case GregorianCalendar.WEDNESDAY: tag = "Mittwoch"; break; case GregorianCalendar.THURSDAY: tag = "Donnerstag"; break; case GregorianCalendar.FRIDAY: tag = "Freitag"; break; } int i = 0; while (i <= 10) { File f = new File("/sdcard/" + i + tag + "fach.txt"); if(!f.exists()) break; i++; } i--; int endHr = 0; int endMin = 0; switch (i) { case 0: endHr = 8; endMin = 30; break; case 1: endHr = 9; endMin = 20; break; case 2: endHr = 10; endMin = 20; break; case 3: endHr = 11; endMin = 10; break; case 4: endHr = 12; endMin = 5; break; case 5: endHr = 12; endMin = 55; break; case 6: endHr = 13; endMin = 55; break; case 7: endHr = 14; endMin = 45; break; case 8: endHr = 15; endMin = 35; break; case 9: endHr = 16; endMin = 25; break; case 10: endHr = 17; endMin = 15; break; } if (cal.get(GregorianCalendar.HOUR_OF_DAY) < endHr) { audioManager.setRingerMode(AudioManager.RINGER_MODE_VIBRATE); } else if (cal.get(GregorianCalendar.HOUR_OF_DAY) == endHr && cal.get(GregorianCalendar.MINUTE) <= endMin + 5) { audioManager.setRingerMode(AudioManager.RINGER_MODE_VIBRATE); } else { int maxVolume = audioManager.getStreamMaxVolume(AudioManager.STREAM_RING); if (audioManager.getRingerMode() == AudioManager.RINGER_MODE_VIBRATE || audioManager.getRingerMode() == AudioManager.RINGER_MODE_SILENT) { audioManager.setRingerMode(AudioManager.RINGER_MODE_NORMAL); audioManager.setStreamVolume(AudioManager.STREAM_RING, maxVolume, AudioManager.FLAG_SHOW_UI + AudioManager.FLAG_PLAY_SOUND); } } } } }
logcat的：
08-30 12:44:04.508 23294-23294/de.nathan.android.droidschool D/AndroidRuntime: Shutting down VM 08-30 12:44:04.508 23294-23294/de.nathan.android.droidschool W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x41ce6700) 08-30 12:44:04.538 23294-23294/de.nathan.android.droidschool E/AndroidRuntime: FATAL EXCEPTION: main java.lang.RuntimeException: Unable to instantiate service de.nathan.android.droidschool.MuteService: java.lang.NullPointerException at android.app.ActivityThread.handleCreateService(ActivityThread.java:2561) at android.app.ActivityThread.access$1600(ActivityThread.java:141) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1338) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5103) 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:737) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.NullPointerException at android.content.ContextWrapper.getSystemService(ContextWrapper.java:519) at de.nathan.android.droidschool.MuteService.(MuteService.java:21) at java.lang.Class.newInstanceImpl(Native Method) at java.lang.Class.newInstance(Class.java:1130) at android.app.ActivityThread.handleCreateService(ActivityThread.java:2558) ... 10 more 08-30 12:44:04.548 440-1477/? W/ActivityManager: Force finishing activity de.nathan.android.droidschool/.MainActivity 08-30 12:44:04.848 440-1477/? I/WindowManager: Screenshot max retries 4 of Token{42d5f4e8 ActivityRecord{42624258 u0 de.nathan.android.droidschool/.MainActivity}} appWin=Window{42cc6e50 u0 Starting de.nathan.android.droidschool} drawState=4 08-30 12:44:05.358 440-458/? W/ActivityManager: Activity pause timeout for ActivityRecord{42624258 u0 de.nathan.android.droidschool/.MainActivity} 08-30 12:44:07.068 440-458/? W/ActivityManager: Timeout executing service: ServiceRecord{4330adf8 u0 de.nathan.android.droidschool/.MuteService} 08-30 12:44:07.068 440-458/? I/ActivityManager: Crashing app skipping ANR: ProcessRecord{42cf6020 23294:de.nathan.android.droidschool/u0a10018} Executing service de.nathan.android.droidschool/.MuteService 08-30 12:44:15.518 440-458/? W/ActivityManager: Activity destroy timeout for ActivityRecord{42624258 u0 de.nathan.android.droidschool/.MainActivity}
Timer myTimer = new Timer(); MyTimerTask myTimerTask= new MyTimerTask(); AudioManager audioManager; public void onCreate() { super.onCreate(); audioManager = (AudioManager)this.getSystemService(Context.AUDIO_SERVICE); }
你需要在onCreate中初始化audioManager。
绝对是这样的：
AudioManager audioManager = (AudioManager)this.getSystemService(Context.AUDIO_SERVICE);
做这个：
AudioManager audioManager = (AudioManager)getApplicationContext().getSystemService(Context.AUDIO_SERVICE);