android - 使用AlertDialog时捕获异常？

Question

我试图将我的alertdialog与我的主类放在一个单独的类中，并且当它被调用时它也会得到并且错误并且应用程序停止，我想知道我将如何捕获异常或如何在代码中发现错误像这样。

这是警报对话框的代码:

import android.app.AlertDialog;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

public class PlacepinDialog extends AlertDialog{

    AlertDialog.Builder builder;
    AlertDialog alertDialog;
    TextView text;
    ImageView image;
    Button place;
    Button cancel;
    LayoutInflater inflater;
    View layout;

    public PlacepinDialog(Context context) {
        super(context);
        //Setting up View and Inflater
        LayoutInflater inflater = (LayoutInflater)getLayoutInflater();
        View layout = inflater.inflate(R.layout.placepin_dialog,
                (ViewGroup) findViewById(R.id.mvMain));

        //Text Views
        TextView text = (TextView) layout.findViewById(R.id.Placetext);
        text.setText("Do you want to place a pin at the location you pressed?");

        //Image Views
        ImageView image = (ImageView) layout.findViewById(R.id.Placeimage);
        image.setImageResource(R.drawable.icon);

        //Building the Dialog
        builder = new AlertDialog.Builder(context);
        builder.setView(layout);
        alertDialog.setTitle("Place Pin");
        alertDialog = builder.create();
    }
    }

这是调用alertdialog的地方(此onTouchEvent在与主类不同的其他类中，所以我不能只做main.this):

public boolean onTouchEvent(MotionEvent e, MapView mv){
        int i = e.getAction();

        switch(i){

        case MotionEvent.ACTION_DOWN:
            //When your finger touches the screen
            Log.d("ACTION DOWN", "Finger touched screen");

            break;

        case MotionEvent.ACTION_UP:
            //When your finger stop touching the screen
            Log.d("ACTION UP", "Finger was removed from screen");
            try{
            PlacepinDialog alertDialog = new PlacepinDialog(null);
            }
            catch(){

            }
            break;

        case MotionEvent.ACTION_MOVE:
            //When your finger moves around the screen
            Log.d("ACTION MOVE", "Finger was moved around the screen");

            break;
        }

        return false;
    }

Answer 1

您将上下文传递为null，这就是问题所在。给出一些适当的值，您可能不会得到它。

    PlacepinDialog alertDialog = new PlacepinDialog(null);

public PlacepinDialog(Context context)

builder = new AlertDialog.Builder(context); // context is null.

这些行是从您的代码中选择的。这引起了问题。