用戶在退出應用前給出一個提示是很有必要的,因爲可能是用戶並不真的想退出,而只是一不小心按下了返回鍵,大部分應用也是這麼做的,但也有些應用的做法是在應用退出去前給出一個Dialog,我覺得這樣不太友好,用戶還得移動手指去按dialog中的“確定”按鈕。我覺得再按一次“返回”鍵退出程序是佳的用戶體驗,實現也很簡單,代碼如下:
private long exitTime = 0;
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(keyCode == KeyEvent.KEYCODE_BACK && event.getAction() == KeyEvent.ACTION_DOWN){
if((System.currentTimeMillis()-exitTime) > 2000){
Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();
exitTime = System.currentTimeMillis();
} else {
finish();
System.exit(0);
}
return true;
}
return super.onKeyDown(keyCode, event);
}
</pre><pre name="code" class="java">或者
<span style="white-space:pre"> </span>private long exitTime = 0;
<span style="white-space:pre"> </span>@Override
<span style="white-space:pre"> </span>public boolean onKeyDown(int keyCode, KeyEvent event) {
<span style="white-space:pre"> </span>// TODO Auto-generated method stub
<span style="white-space:pre"> </span>switch (keyCode) {
<span style="white-space:pre"> </span>case KeyEvent.KEYCODE_BACK:
<span style="white-space:pre"> </span>if ((System.currentTimeMillis() - exitTime) > 2000) {
<span style="white-space:pre"> </span>toast("再按一次返回鍵退出程序!");
<span style="white-space:pre"> </span>exitTime = System.currentTimeMillis();
<span style="white-space:pre"> </span>return false;
<span style="white-space:pre"> </span>} else {
<span style="white-space:pre"> </span>finish();
<span style="white-space:pre"> </span>System.exit(0);
<span style="white-space:pre"> </span>}
<span style="white-space:pre"> </span>break;
<span style="white-space:pre"> </span>default:
<span style="white-space:pre"> </span>break;
<span style="white-space:pre"> </span>}
<span style="white-space:pre"> </span>return super.onKeyDown(keyCode, event);
<span style="white-space:pre"> </span>}
</pre><pre name="code" class="java"><span style="font-family:Arial, Helvetica, sans-serif;"><span style="white-space: normal;">
</span></span>