重寫dispatchKeyEvent方法 按返回鍵back 執行兩次的解決方法

@Override
	public boolean dispatchKeyEvent(KeyEvent event) {
		if(event.getKeyCode() == KeyEvent.KEYCODE_BACK && event.getAction() != KeyEvent.ACTION_UP) {//不響應按鍵擡起時的動作 
			//TODO 代碼  
			System.out.println("Back pressed. event.getKeyCode() => " + event.getKeyCode() + ", event.getKeyCode() => " + event.getAction());
            return true;//注意這兒返回值爲true時該事件將不會繼續往下傳遞，false時反之。根據程序的需要調整
		}
		return super.dispatchKeyEvent(event);
	}