Android widget onReceive崩溃

Question

基本上，当我单击小部件上的特定按钮时，我希望获取数据库中的下一条记录。该功能本身的工作很好，因为我在应用程序中使用它。但在小部件中，它崩溃了。我认为问题出在onReceive函数本身，尽管即使我只是设置onReceive来更新textview，它也会崩溃为NullPointerException。

公共静态字符串NEXT_RECORD=“NEXT_RECORD”；

以下是它的名称：

Intent Intent=new Intent（context,myWidgetProvider.class）；
Intent.setaction(NEXT_RECORD)；PendingIntent PendingIntent=PendingIntent.getbroadcast（上下文，0，intent，PendingIntent.flag_update_current)；remoteviews.setonClickPendingIntent(r.id.textview02,pendingIntent）；

  @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)

如果newid=mdbhelper.getnextrecord(1,keyid）；抛出此NPE，则mdbhelper为空。在尝试读取MDBHelper之前，只需实例化它：

@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);
    }

}