异步任务不执行

对此不熟悉，但我看不到任何问题。在设置中有一个复选框来启动异步任务，因此onCreate中的if语句。我只是在执行任务的行上发生Java null错误。异步任务不执行

代码

ProgressDialog progressDialog; 
double longitude, latitude; 
Location location; 

private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters 


private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute 


protected LocationManager locationManager; 

GPSLocation task = new GPSLocation(); 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_confirm_screen); 
    SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this); 
    Boolean locationCheck = sp.getBoolean("LOCATION", false); 
    if(locationCheck){ 

     task.execute(); 
    } 
    else 
    { 
    sendEmail(); 
    playSound(); 
    } 

} 

public double getLatitude() 
{ 
    if (location != null) 
    { 
     latitude = location.getLatitude(); 
    } 

    return latitude; 
} 

public double getLongitude() 
{ 
    if (location != null) 
    { 
     longitude = location.getLongitude(); 
    } 
    return longitude; 
} 

public class GPSLocation extends AsyncTask<Void, Void, Void> implements LocationListener 
{ 
    boolean running =true; 
      @Override 
      protected void onPreExecute() 
      { 
       super.onPreExecute(); 
       progressDialog = new ProgressDialog(ConfirmScreen.this); 
       progressDialog.setOnCancelListener(new DialogInterface.OnCancelListener(){ 
         public void onCancel(DialogInterface dialog) { 
          //getgps.cancel(true); 
         } 
       }); 

       locationManager.requestLocationUpdates(
         LocationManager.GPS_PROVIDER, 
         MIN_TIME_BW_UPDATES, 
         MIN_DISTANCE_CHANGE_FOR_UPDATES, this); 
       Log.d("GPS Enabled", "GPS Enabled"); 
       if (locationManager != null) { 
        location = locationManager.getLastKnownLocation(LocationManager.GPS_PROVIDER); 
          if (location != null) { 
            latitude = location.getLatitude(); 
            longitude = location.getLongitude(); 
            progressDialog.setCancelable(true); 
            progressDialog.setMessage("Getting GPS Location..."); 
            progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER); 
            progressDialog.setProgress(1); 
            progressDialog.show(); 
          } 
       } 

      } 

      @Override 
      protected void onProgressUpdate(Void... values) { 
       super.onProgressUpdate(values); 
       // Things to be done while execution of long running operation is in progress. For example updating ProgessDialog 
      } 

      @Override 
      protected void onPostExecute(Void result) 
      { 
        progressDialog.cancel(); 
        sendEmail("GPS: ", Double.toString(longitude).trim(), Double.toString(latitude).trim()); 
        playSound(); 
      } 

      @Override 
      protected Void doInBackground(Void... params) { 
       boolean isDataSubmitted = false; 

       while(!isDataSubmitted) 
       { 
        if(longitude !=0 && latitude!=0) 
        { 
         sendEmail(); //Send Email without co-ords 
         playSound(); 
         isDataSubmitted = true; 
        } 
       } 

       return null;  
      } 

      @Override 
      public void onLocationChanged(Location location) { 
       // TODO Auto-generated method stub 

      } 

      @Override 
      public void onProviderDisabled(String provider) { 
       // TODO Auto-generated method stub 

      } 

      @Override 
      public void onProviderEnabled(String provider) { 
       // TODO Auto-generated method stub 

      } 

      @Override 
      public void onStatusChanged(String provider, int status, 
        Bundle extras) { 
       // TODO Auto-generated method stub 

      } 
} 


public void backHome(View view) 
{ 
    Intent intent = new Intent (this, MainScreen.class); 
    startActivity(intent); 
} 

// Method to start playing and looping a sound. 

public void playSound() 
{ 
    MediaPlayer clickSound = MediaPlayer.create(this, R.raw.warning); 
    SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this); 
    Boolean soundCheck = sp.getBoolean("SOUND", false); 
    if (soundCheck) 
    { 
     clickSound.start(); 
    } 



}// method end 

public void sendEmail() 
{ 
    SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this); 
    String nameValue = sp.getString("NAME", "failed to get name"); 
    String emailValue = sp.getString("EMAIL", "failed to get email"); 
    Intent i = new Intent(Intent.ACTION_SEND); 
    i.setType("message/rfc822"); 
    i.putExtra(Intent.EXTRA_EMAIL, new String[]{emailValue}); 
    i.putExtra(Intent.EXTRA_SUBJECT, "Email sent from DON'T PANIC - A Chris O'Brien Project"); 
    i.putExtra(Intent.EXTRA_TEXT, "Hi there\n" + nameValue + " is in mortal danger. They didn't include co-ords as they assume you know where they are..\nKind Regards\nDon't Panic! \n\n\n"); 

    try 
    { startActivity(Intent.createChooser(i, "Send mail....")); 
    } 
    catch (android.content.ActivityNotFoundException ex){ 

     Toast.makeText(ConfirmScreen.this, "There are no email clients installed or set up", Toast.LENGTH_SHORT).show(); 
    } 
} 


public void sendEmail(String a, String b, String c) 
{ 
    SharedPreferences sp = PreferenceManager.getDefaultSharedPreferences(this); 
    String nameValue = sp.getString("NAME", "failed to get name"); 
    String emailValue = sp.getString("EMAIL", "failed to get email"); 
    Intent i = new Intent(Intent.ACTION_SEND); 
    i.setType("message/rfc822"); 
    i.putExtra(Intent.EXTRA_EMAIL, new String[]{emailValue}); 
    i.putExtra(Intent.EXTRA_SUBJECT, "Email sent from DON'T PANIC - A Chris O'Brien Project"); 
    i.putExtra(Intent.EXTRA_TEXT, "Hi there\n" + nameValue + " is in mortal danger. Please see the co-ords attached and run to their rescue!" + 
      " If you don't see any co-ords, they didn't check the box and assume you know where they are.\nKind Regards\nDon't Panic! \n\n\n" + 
      a + b + c); 

    try 
    { startActivity(Intent.createChooser(i, "Send mail....")); 
    } 
    catch (android.content.ActivityNotFoundException ex){ 

     Toast.makeText(ConfirmScreen.this, "There are no email clients installed or set up", Toast.LENGTH_SHORT).show(); 
    } 
} 


@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    getMenuInflater().inflate(R.menu.activity_confirm_screen, menu); 
    return true; 
} 






}

调试信息

10-03 08:38:16.890: D/dalvikvm(27516): Late-enabling CheckJNI 
10-03 08:38:16.990: I/dalvikvm(27516): Turning on JNI app bug workarounds for target SDK version 11... 
10-03 08:38:17.030: E/Trace(27516): error opening trace file: No such file or directory (2) 
10-03 08:38:17.600: D/dalvikvm(27516): GC_FOR_ALLOC freed 58K, 9% free 12206K/13315K, paused 105ms, total 111ms 
10-03 08:38:17.610: I/dalvikvm-heap(27516): Grow heap (frag case) to 13.616MB for 784248-byte allocation 
10-03 08:38:17.755: D/dalvikvm(27516): GC_CONCURRENT freed 1K, 8% free 12971K/14087K, paused 35ms+9ms, total 147ms 
10-03 08:38:17.940: D/dalvikvm(27516): GC_FOR_ALLOC freed 0K, 8% free 12971K/14087K, paused 32ms, total 32ms 
10-03 08:38:17.985: I/dalvikvm-heap(27516): Grow heap (frag case) to 16.606MB for 3136944-byte allocation 
10-03 08:38:18.025: D/dalvikvm(27516): GC_CONCURRENT freed 0K, 7% free 16034K/17159K, paused 24ms+1ms, total 40ms 
10-03 08:38:18.025: D/dalvikvm(27516): WAIT_FOR_CONCURRENT_GC blocked 4ms 
10-03 08:39:44.110: E/SpannableStringBuilder(27516): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length 
10-03 08:39:44.110: E/SpannableStringBuilder(27516): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length 
10-03 08:39:45.145: E/SpannableStringBuilder(27516): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length 
10-03 08:39:45.145: E/SpannableStringBuilder(27516): SPAN_EXCLUSIVE_EXCLUSIVE spans cannot have a zero length 
10-03 08:39:45.910: D/dalvikvm(27516): GC_FOR_ALLOC freed 815K, 11% free 15718K/17543K, paused 9ms, total 9ms 
10-03 08:39:45.910: I/dalvikvm-heap(27516): Grow heap (frag case) to 19.016MB for 2850872-byte allocation 
10-03 08:39:45.925: D/dalvikvm(27516): GC_CONCURRENT freed 10K, 10% free 18492K/20359K, paused 1ms+1ms, total 12ms 
10-03 08:39:45.955: D/dalvikvm(27516): GC_FOR_ALLOC freed 0K, 10% free 18492K/20359K, paused 9ms, total 9ms 
10-03 08:39:45.970: I/dalvikvm-heap(27516): Grow heap (frag case) to 29.882MB for 11403440-byte allocation 
10-03 08:39:45.990: D/dalvikvm(27516): GC_CONCURRENT freed 0K, 7% free 29628K/31559K, paused 11ms+2ms, total 22ms 
10-03 08:39:46.025: D/AndroidRuntime(27516): Shutting down VM 
10-03 08:39:46.025: W/dalvikvm(27516): threadid=1: thread exiting with uncaught exception (group=0x41d77300) 
10-03 08:39:46.035: E/AndroidRuntime(27516): FATAL EXCEPTION: main 
10-03 08:39:46.035: E/AndroidRuntime(27516): java.lang.RuntimeException: Unable to start activity ComponentInfo{cs4084.panic.button/cs4084.panic.button.ConfirmScreen}: java.lang.NullPointerException 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.ActivityThread.access$600(ActivityThread.java:140) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.os.Handler.dispatchMessage(Handler.java:99) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.os.Looper.loop(Looper.java:137) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.ActivityThread.main(ActivityThread.java:4898) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at java.lang.reflect.Method.invokeNative(Native Method) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at java.lang.reflect.Method.invoke(Method.java:511) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at dalvik.system.NativeStart.main(Native Method) 
10-03 08:39:46.035: E/AndroidRuntime(27516): Caused by: java.lang.NullPointerException 
10-03 08:39:46.035: E/AndroidRuntime(27516): at cs4084.panic.button.ConfirmScreen$GPSLocation.onPreExecute(ConfirmScreen.java:89) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.os.AsyncTask.execute(AsyncTask.java:534) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at cs4084.panic.button.ConfirmScreen.onCreate(ConfirmScreen.java:46) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.Activity.performCreate(Activity.java:5184) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1083) 
10-03 08:39:46.035: E/AndroidRuntime(27516): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064) 
10-03 08:39:46.035: E/AndroidRuntime(27516): ... 11 more

来源

2012-10-03 Chris O' Brien

我觉得你越来越在onPreExecute方法一个空指针，所以我猜的LocationManager为空，尝试将其初始化为onCreate（）方法。

locationManager = (LocationManager) this 
      .getSystemService(Context.LOCATION_SERVICE);

希望这可以解决空错误问题。

来源

2012-10-03 07:50:27

我爱你。 :) 它对它进行排序，它现在正在工作，只是进度对话框没有弹出，但我认为这取决于我允许它使用最后一个已知的位置。我会为此努力。 –

看来你还没有实例化你的LocationManager，使用

LocationManager locationManager = (LocationManager) this.getSystemService(Context.LOCATION_SERVICE);

来源

2012-10-03 07:52:53

我也爱你，但我看到他的第一个:) –

您还没有初始化locationManager 要解决这个问题，在您的onCreate方法，你可以这样做：

locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

来源

2012-10-03 07:54:20 Sameer

异步任务不执行

回答

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