Android alertdialogで終了確認

package com.example.alertdialog;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.view.Menu;
import android.view.View;
import android.widget.Toast;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

//     onBackPressed,             ，      。
    public void onBackPressed1(View v) { 
        new AlertDialog.Builder(this).setTitle("     ？") 
            .setIcon(android.R.drawable.ic_dialog_info) 
            .setPositiveButton("  ", new DialogInterface.OnClickListener() { 
         
                @Override 
                public void onClick(DialogInterface dialog, int which) { 
                //   “  ”     
                    MainActivity.this.finish(); 
         
                } 
            }) 
            .setNegativeButton("  ", new DialogInterface.OnClickListener() { 
         
                @Override 
                public void onClick(DialogInterface dialog, int which) { 
                //   “  ”    ,            
                    Toast.makeText(MainActivity.this, "       ", Toast.LENGTH_LONG).show();
                } 
            }).show(); 
           }
    
}