問題一、cookie同步問題

有一個需求，在android中需要通過webview開啟h5頁面，並且需要把登入狀態帶到h5頁面中，可以通過給webview要載入的url設定cookie的方式，同步登入狀態。程式碼如下：

public void synCookies(Context context, String url) {
        CookieManager cookieManager = CookieManager.getInstance();
        cookieManager.setAcceptCookie(true);
        cookieManager.setCookie
 
(url, cookies);//cookies是在HttpClient中獲得的cookie
        String c = cookieManager.getCookie(url);
        Log.v(TAG,"=======cookies"+c);
        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {

            CookieSyncManager.createInstance(getApplicationContext());
            CookieSyncManager.getInstance
 
().sync();
        } else {
            cookieManager.flush();
        }
    }

這裡當時遇到一個問題，看別人寫的會在setCookie(url,cookies)之前呼叫cookieManager.removeSessionCookies()方法清除cookie。
這種情況下在android4.3的真機和模擬器上均會出現登入狀態同步失敗的問題。
去檢視原始碼發現，cookieManager.removeSessionCookie();

 /**
     * Removes all session cookies, which are cookies without
 
 an expiration
     * date.
     * <p>
     * This method is asynchronous.
     * If a {@link ValueCallback} is provided,
     * {@link ValueCallback#onReceiveValue(T) onReceiveValue()} will be called on the current
     * thread's {@link android.os.Looper} once the operation is complete.
     * The value provided to the callback indicates whether any cookies were removed.
     * You can pass {@code null} as the callback if you don't need to know when the operation
     * completes or whether any cookie were removed, and in this case it is safe to call the
     * method from a thread without a Looper.
     * @param callback a callback which is executed when the session cookies have been removed
     */
    public abstract void removeSessionCookies(ValueCallback<Boolean> callback);

此方法會清除沒有過期時間的cookie，（至於為什麼沒有同步成功，還沒弄清楚）如果想清除cookie可以呼叫removeAllCookie()，這時就可以同步成功了。

另外也可以不呼叫此方法，因為呼叫setCookie()的時候,會把原來的相同的cookie替換掉。