Android小部件onReceive崩潰

Question

基本上，當我單擊窗口小部件上的特定按鈕時，我想獲取數據庫中的下一條記錄。 當我在應用程序中使用該功能時，該功能本身可以正常工作。 但是在小部件中它崩潰了。 我以為是onReceive函數本身就是問題所在，盡管即使我只是將onReceive設置為更新文本視圖，它也會由於nullpointerexception崩潰而崩潰。

公共靜態字符串NEXT_RECORD =“ next_record”;

這是它的調用位置：

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

並在收到

  @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); 拋出該NPE，則mDbHelper為null。 只需實例化mDbHelper然后再嘗試從中讀取：

@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);
    }

}