android - 在android小部件中从数据库获取数据

Question

我已经为我的小部件创建了一个类，它应该从我的应用程序的数据库中获取数据，但我在获取数据时遇到问题...这是我的类

public class AppWidget extends AppWidgetProvider {
private static DBAdapter mDbHelper;
@Override
public void onReceive(Context ctxt, Intent intent)
{
    if(intent.getAction()==null)
    {
        ctxt.startService(new Intent (ctxt,ToggleService.class));
    }
    else
    {
        super.onReceive(ctxt,intent);
    }

}
@Override
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds)
{

    context.startService(new Intent(context,ToggleService.class));
}

public static void updateWidgetContent(Context context,
    AppWidgetManager appWidgetManager, int[] appWidgetIds) {

}
private static DBAdapter getDatabaseHelper(Context context) {
    DBAdapter dbh = null;
    if (dbh == null) {
        dbh = new DBAdapter(context);
        dbh.open();
    }
    return dbh;
}
public static class ToggleService extends IntentService
{
    public ToggleService()
    {
        super("AppWidget$ToggleService");
    }

    @Override
    protected void onHandleIntent(Intent intent)
    {
        ComponentName me= new ComponentName(this,AppWidget.class);
        AppWidgetManager mgr= AppWidgetManager.getInstance(this);
        mgr.updateAppWidget(me,buildUpdate(this));
    }

    private RemoteViews buildUpdate(Context context)
    {
        RemoteViews updateViews= new RemoteViews(context.getPackageName(),R.layout.widget);


        Calendar c = Calendar.getInstance();
        SimpleDateFormat dateFormat= new SimpleDateFormat("yyyyMMdd");
        String dateForButton= dateFormat.format(c.getTime());
        Cursor ce= mDbHelper.fetchReminder(Integer.parseInt(dateForButton));
        ce.moveToFirst();
        //startManagingCursor(ce);

        updateViews.setTextViewText(R.id.dd,ce.getString(ce.getColumnIndexOrThrow(DBAdapter.KEY_de)));
        updateViews.setTextViewText(R.id.tt,"test2");
        updateViews.setTextViewText(R.id.ss,"test1");
        Intent i= new Intent(this, AppWidget.class);
        PendingIntent pi=  PendingIntent.getBroadcast(context, 0, i, 0);
        updateViews.setOnClickPendingIntent(R.id.kr, pi);
        return updateViews;

    }
}
 }

在 list 中，一切都应该是这样，我已经创建了接收器和服务，在我添加带有光标的行之前，小部件显示在主屏幕上，但现在包含光标代码，它会导致应用程序崩溃并抛出空点IntentService 异常

Answer 1

我认为错误的是你应该编写这行代码

      mDbHelper=getDatabaseHelper(this);

之前

   Cursor ce= mDbHelper.fetchReminder(Integer.parseInt(dateForButton));

因为您已经定义了方法 getDatabaseHelper