代码不等待回调函数完成答案

【问题标题】：Code doesn't wait for Callback Function Completion代码不等待回调函数完成
【发布时间】：2012-07-22 08:39:48
【问题描述】：

我是来自 Java 的 Javascript 新手，我想编写一个功能类似于 Java 方法的函数。问题是调用代码不会等待被调用函数完成，而是继续发生错误。我希望你明白我在说什么。也许你可以帮助我

if (Titanium.Facebook.loggedIn) {
        // User is not logged in with his ACS Account but with its Facebook Account
        // now we can check if he has an ACS Account with the same eMail Address
        Titanium.API.info('User seems to be logged in to Facebook');

        gFacebookAccount = gFacebookController.getLoggedInFacebookAccount();
        Titanium.API.info('Logged In Facebook Account is : '+ gFacebookAccount); }

调用的 getLoggedInFacebookAccount 看起来像这样。我试图通过超时循环延迟该方法不起作用。

exports.getLoggedInFacebookAccount = function()
{
Titanium.API.info('Started getLoggedInFacebookAccount');
var lCallBackFinished = false;
var lActualUser = null;
Titanium.Facebook.requestWithGraphPath('me', {}, 'GET', handleGraphRequestCallback);

waitForQueryCallback();


function waitForQueryCallback() {
    if (!lCallBackFinished) {
        Titanium.API.info('Wait for Query Callback Loop');
        setTimeout(waitForQueryCallback, 100);
        //
    }
    else
    {
        return lActualUser;
    }
}


function handleGraphRequestCallback(pGraphCallback) {

// damn callbacks - now here the user is logged in
// and the Graph Request is (sucessfully or not) finished

Titanium.API.info('Start handleGraphRequest-Callback');
if (pGraphCallback.success) {
    Titanium.API.info('Graph Request Callback Sucessful');
    lActualUser = pGraphCallback.result;

} else {
    Titanium.API.info('Graph Request Callback Not Sucessful');

}

lCallBackFinished = true;

}

}

控制台输出是：

[INFO][TiAPI   (  301)] User seems to be logged in to Facebook
[INFO][TiAPI   (  301)] Started getLoggedInFacebookAccount
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][TiAPI   (  301)] Logged In Facebook Account is : undefined
[INFO][TiAPI   (  301)] Function called
[ERROR][TiJSError(  301)] (main) [214,2413] ----- Titanium Javascript Runtime Error -----
[ERROR][TiJSError(  301)] (main) [0,2413] - In undefined:1,1

[ERROR][TiJSError(  301)] (main) [0,2413] - Message: Uncaught SyntaxError: Unexpected token u
[ERROR][TiJSError(  301)] (main) [1,2414] - Source: undefined
[ERROR][V8Exception(  301)] Exception occurred at undefined:1: Uncaught SyntaxError: Unexpected token u
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][TiRootActivity(  301)] (main) [0,0] checkpoint, on root activity resume. activity = de.dosofun.knowitall.Knowitall2Activity@44ede8f8
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][ARMAssembler(   60)] generated scanline__00000077:03515104_00000000_00000000 [ 33 ipp] (47 ins) at [0x3666d0:0x36678c] in 4662744 ns
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][ActivityManager(   60)] Displayed activity de.dosofun.knowitall/.Knowitall2Activity: 5509 ms (total 5509 ms)
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][TiAPI   (  301)] Wait for Query Callback Loop
[INFO][TiAPI   (  301)] Start handleGraphRequest-Callback
[INFO][TiAPI   (  301)] Graph Request Callback Sucessful

行的原因：[INFO][TiAPI (301)] 登录 Facebook 帐户是：未定义您可以看到代码不会等到调用的方法完成。

什么是必要的，这样我的代码才能按预期工作，如果我的代码很糟糕，有什么更好的方法（不会让人难以阅读）

感谢您的帮助

【问题讨论】：

是否直接返回'lActualUser'？

标签： javascript function callback console timeout

【解决方案1】：

wait_var = waitForQueryCallback();
YOU ARE NOT HANDLING THE RETURN FROM waitForQueryCallback() here...

function waitForQueryCallback() {
if (!lCallBackFinished) {
    Titanium.API.info('Wait for Query Callback Loop');
    setTimeout(waitForQueryCallback, 100);
    //
    RETURN SOMETHING HERE?
}
else
{
    return lActualUser;
}
}

尝试处理 waitForQueryCallback() 中的 wait_var 并在回调未完成时返回。

【讨论】：