同時開啓GPS，我得到空指針異常

你好，我是第一次用的LocationManager檢查GPS是否啓用或不同時開啓GPS，我得到空指針異常

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

     // getting GPS status 
     isGPSEnabled = locationManager 
       .isProviderEnabled(LocationManager.GPS_PROVIDER);

和我一樣使用

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />

現在的權限，如果GPS不可啓用比我打開一個對話框說，你想啓用GPS？

 final AlertDialog.Builder builder = new AlertDialog.Builder(this); 
builder.setMessage("Yout GPS seems to be disabled, do you want to enable it?") 
     .setCancelable(false) 
     .setPositiveButton("Yes", new DialogInterface.OnClickListener() { 
      public void onClick(@SuppressWarnings("unused") final DialogInterface dialog, @SuppressWarnings("unused") final int id) { 
       startActivity(new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS)); 
      } 
     }) 
     .setNegativeButton("No", new DialogInterface.OnClickListener() { 
      public void onClick(final DialogInterface dialog, @SuppressWarnings("unused") final int id) { 
       dialog.cancel(); 
      } 
     }); 
final AlertDialog alert = builder.create(); 
alert.show();

，但我在我的logcat獲得空指針異常是）低於

09-09 09:46:04.599: W/System.err(935): java.lang.NullPointerException 
    09-09 09:46:04.599: W/System.err(935): at android.content.ContextWrapper.getSystemService(ContextWrapper.java:363) 
    09-09 09:46:04.599: W/System.err(935): at com.android.internal.app.AlertController$AlertParams.<init>(AlertController.java:742) 
    09-09 09:46:04.599: W/System.err(935): at android.app.AlertDialog$Builder.<init>(AlertDialog.java:283) 
    09-09 09:46:04.599: W/System.err(935): at android.app.AlertDialog$Builder.<init>(AlertDialog.java:274) 
    09-09 09:46:04.599: W/System.err(935): at com.eheuristics.android.diegodeals.googleplacesandmaps.GPSTracker.turnGPSOn(GPSTracker.java:110) 
    09-09 09:46:04.599: W/System.err(935): at com.eheuristics.android.diegodeals.googleplacesandmaps.GPSTracker.getLocation(GPSTracker.java:63) 
    09-09 09:46:04.599: W/System.err(935): at com.eheuristics.android.diegodeals.googleplacesandmaps.GPSTracker.<init>(GPSTracker.java:45) 
    09-09 09:46:04.599: W/System.err(935):  at com.eheuristics.android.diegodeals.NearestLocation.onCreate(NearestLocation.java:79) 
    09-09 09:46:04.599: W/System.err(935): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 
    09-09 09:46:04.599: W/System.err(935): at android app.ActivityThread.performLaunchActivity(ActivityThread.java:1722) 
    09-09 09:46:04.599: W/System.err(935): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1784) 
    09-09 09:46:04.599: W/System.err(935): at android.app.ActivityThread.access$1500(ActivityThread.java:123) 
    09-09 09:46:04.599: W/System.err(935): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:939) 
    09-09 09:46:04.599: W/System.err(935): at android.os.Handler.dispatchMessage(Handler.java:99) 
    09-09 09:46:04.599: W/System.err(935): at android.os.Looper.loop(Looper.java:130) 
    09-09 09:46:04.609: W/System.err(935): at android.app.ActivityThread.main(ActivityThread.java:3835) 
    09-09 09:46:04.609: W/System.err(935): at java.lang.reflect.Method.invokeNative(Native Method) 
    09-09 09:46:04.609: W/System.err(935): at java.lang.reflect.Method.invoke(Method.java:507) 
    09-09 09:46:04.609: W/System.err(935): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:864)

來源

2012-09-09 Siddhpura Amit

mContext爲空，我猜 – Braj

你的mContext可能爲null。確保你的mContext不爲null –

如果mContext爲空，那麼我得到的錯誤是行na！ –

嘗試使用getApplicationContext（而不是mContext。

來源

2012-09-09 06:36:36 Sandeep

同時開啓GPS，我得到空指針異常

回答

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