[Android] 뒤로가기 버튼을 누를시 경고창

public boolean onKeyDown(int keyCode, KeyEvent event){
	     switch(keyCode){
	     case KeyEvent.KEYCODE_BACK:
	      String alertTitle = getResources().getString(R.string.app_name);
	      String buttonMessage = "어플을 종료하시겠습니까?";
	      String buttonYes = "Yes";
	      String buttonNo = "No";
	         
	      new AlertDialog.Builder(WriteActivity.this)
	      .setTitle(alertTitle)
	      .setMessage(buttonMessage)
	      .setPositiveButton(buttonYes, new DialogInterface.OnClickListener() {
	       
	       @Override
	       public void onClick(DialogInterface dialog, int which) {
	        // TODO Auto-generated method stub
	        moveTaskToBack(true);
	        finish();
	       }
	      })
	      .setNegativeButton(buttonNo, null)
	      .show();
	     }
	    return true; 

     }

이 메소드를 추가시켜주면 됩니다.