android 返回鍵退出程序

在mainActivity裏寫事件

@Override
    public boolean dispatchKeyEvent(KeyEvent event) {
        System.out.println(KeyEvent.KEYCODE_BACK+"--------------------"+event.getKeyCode()+"---------------------"+event.getAction());
        if(event.getKeyCode()==KeyEvent.KEYCODE_BACK && event.getAction()==KeyEvent.ACTION_DOWN){
        	 // 確認對話框
	    	   final AlertDialog isExit = new AlertDialog.Builder(this).create();
	    	   // 對話框標題
	    	   isExit.setTitle("系統提示");
	    	   // 對話框消息
	    	   isExit.setMessage("確定要退出嗎");
	    	   // 實例化對話框上的按鈕點擊事件監聽
	    	   DialogInterface.OnClickListener listener = new DialogInterface.OnClickListener() {
	    	    @Override
				public void onClick(DialogInterface dialog, int which) {
	    	     switch (which) {
	    	     case DialogInterface.BUTTON1:// "確認"按鈕退出程序
	    	       MainActivity.this.finish();
	    	       android.os.Process.killProcess(android.os.Process.myPid());
	    	       System.exit(0);
	    	      break;
	    	     case DialogInterface.BUTTON2:// "取消"第二個按鈕取消對話框
	    	      isExit.cancel();
	    	      break;
	    	     default:
	    	      break;
	    	     }
	    	    }
	    	   };
	    	   // 註冊監聽
	    	   isExit.setButton("確定", listener);
	    	   isExit.setButton2("取消", listener);
	    	   // 顯示對話框
	    	   isExit.show();
	    	   return true;
        }
        return super.dispatchKeyEvent(event);
    }