Android小部件onReceive崩溃

Question

Basically when I click a particular button on the widget I want to fetch the next record in the database. The function itself works fine as I use it in the app. But in the widget it's crashing. I'm thinking it's the onReceive function itself that is the problem though as even I just set the onReceive to update a textview it crashes as nullpointerexception.

public static String NEXT_RECORD = "next_record";

Here is where it gets called:

Intent intent = new Intent(context, MyWidgetProvider.class);
intent.setAction(NEXT_RECORD); PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT); remoteViews.setOnClickPendingIntent(R.id.TextView02, pendingIntent);

and onreceive

  @Override
  public void onReceive(Context context, Intent intent) {
   super.onReceive(context, intent);
   if(NEXT_RECORD.equals(intent.getAction())){
       newid = mDbHelper.getNextRecord(1, keyid);
    }

  }



04-12 14:47:57.591: E/AndroidRuntime(30633): FATAL EXCEPTION: main
04-12 14:47:57.591: E/AndroidRuntime(30633): java.lang.RuntimeException: Unable to start receiver com.example.app.hs.MyWidgetProvider: java.lang.NullPointerException
04-12 14:47:57.591: E/AndroidRuntime(30633):    at android.app.ActivityThread.handleReceiver(ActivityThread.java:2362)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at android.app.ActivityThread.access$1500(ActivityThread.java:142)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1284)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at android.os.Handler.dispatchMessage(Handler.java:99)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at android.os.Looper.loop(Looper.java:137)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at android.app.ActivityThread.main(ActivityThread.java:4931)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at java.lang.reflect.Method.invokeNative(Native Method)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at java.lang.reflect.Method.invoke(Method.java:511)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:558)
04-12 14:47:57.591: E/AndroidRuntime(30633):    at dalvik.system.NativeStart.main(Native Method)
04-12 14:47:57.591: E/AndroidRuntime(30633): Caused by: java.lang.NullPointerException
04-12 14:47:57.591: E/AndroidRuntime(30633):    at com.example.app.hs.MyWidgetProvider.onReceive(MyWidgetProvider.java:100)

Answer 1

Caused by: java.lang.NullPointerException
    at com.example.app.hs.MyWidgetProvider.onReceive(MyWidgetProvider.java:100)

If newid = mDbHelper.getNextRecord(1, keyid); throws this NPE then mDbHelper is null. Simply instantiate mDbHelper before trying to read from it:

@Override
public void onReceive(Context context, Intent intent) {
    super.onReceive(context, intent);
    if (NEXT_RECORD.equals(intent.getAction())) {
        mDbHelper = new DbHelper(context); // I guessed at the constructor's parameters
        newid = mDbHelper.getNextRecord(1, keyid);
    }

}