如何等待异步HTTP继续之前结束？ [英] How to wait for async http to end before continuing?

问题描述

在GWT有没有什么办法来等待异步调用完成？
我需要应对不断（这是一个登录屏幕，以便更迭意味着改变到实际的游戏和失败意味着停留在登录屏幕）。结果
这里是调用：

In GWT is there any way to wait for asynchronous call to complete? I need the response to continue (It's a login screen so succes means changing to the actual game and failure means staying in the login screen).
Here is the call:

private void execRequest(RequestBuilder builder)
{
    try
    {
        builder.sendRequest(null, new RequestCallback()
        {
            public void onError(Request request, Throwable exception)
            {
                s = exception.getMessage();
            }

            public void onResponseReceived(Request request,
                    Response response)
            {
                s = response.getText();
            }
        });
    } catch (RequestException e)
    {
        s = e.getMessage();
    }
}

这里是调用方法：`

And here is the calling method:`

public String check()
{
    s = null;
    RequestBuilder builder = new RequestBuilder(RequestBuilder.GET, baseUrl
            + "check&user=" + user + "&password=" + password);
    execRequest(builder);
    return s;
}

我需要的检查方法返回的响应（或错误），而不是返回null。结果
我试着写的脑死亡的解决方案：`

I need the check method to return the response (or error) and not to return null.
I tried the brain-dead solution of writing:`

while (s == null);

要等待调用完成，但只是压在发展方式上。结果
（铬说，页面不响应，并建议将其杀死）

To wait for the call to finish but that just crushed the page in development mode.
(chrome said page is unresponsive and suggested to kill it)

推荐答案

拥抱不同步，不打了！

在换句话说：让你的检查异步方法也传递一个回调参数，而不是返回值;并通过回调 execRequest （简单地回调的调用替换每一个分配给取值）。
你不一定需要触发一个应用程序范围的事件总线上的事件，如洁建议：它有助于解耦，但是这并不总是你需要/想干什么

In other words: make your check method asynchronous too, passing a callback argument instead of returning a value; and pass a callback to execRequest (simply replace every assignment to s with a call to the callback). You don't necessarily need to fire an event on an application-wide event bus, as Jai suggested: it helps in decoupling, but that's not always what you need/want.

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