顯示對話框並開始新的活動onBackPressed - Android

Question

如何顯示確認dialog轉到另一個activity後退按鈕？我得到The constructor Intent(new DialogInterface.OnClickListener(){}, Class<MainActivity>) is undefined 錯誤的new Intent(this, MainActivity.class);

@Override 
     public void onBackPressed() { 
        new AlertDialog.Builder(this).setIcon(android.R.drawable.ic_dialog_alert).setTitle("Confirm Navigation") 
          .setMessage("are you sure you want to goto main menu?") 
          .setPositiveButton("Yes", new DialogInterface.OnClickListener() { 
           @Override 
           public void onClick(DialogInterface dialog, int which) { 

            Intent intent = new Intent(this, MainActivity.class); 
            startActivity(intent); 
           } 
          }).setNegativeButton("No", null).show(); 
       } 

Answer 1

更改此

Intent intent = new Intent(this, MainActivity.class); 

到

Intent intent = new Intent(ActivityName.this, MainActivity.class); 

this是不是一個有效的上下文。