Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
1.1k views
in Technique[技术] by (71.8m points)

ajax - UIWebViewDelegate not monitoring XMLHttpRequest?

Is it true that the UIWebViewDelegate does not monitor requests made by using a XMLHttpRequest? If so, is there a way to monitor these kind of requests?

e.g. UIWebViewDelegate does not catch this in -(BOOL) webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSMutableURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType;

var xhr = new XMLHttpRequest();
xhr.open("GET", "http://www.google.com", true);

xhr.onreadystatechange=function() 
{
    if (xhr.readyState==4) 
    {
        alert(xhr.responseText);
    }
}

xhr.send();
Question&Answers:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Answer

0 votes
by (71.8m points)

Interesting question.

There are two parts to make this work: a JavaScript handler and UIWebView delegate methods. In JavaScript, we can modify prototype methods to trigger events when an AJAX request is created. With our UIWebView delegate, we can capture these events.

JavaScript Handler

We need to be notified when an AJAX request is made. I found the solution here.

In our case, to make the code work, I put the following JavaScript in a resource called ajax_handler.js which is bundled with my app.

var s_ajaxListener = new Object();
s_ajaxListener.tempOpen = XMLHttpRequest.prototype.open;
s_ajaxListener.tempSend = XMLHttpRequest.prototype.send;
s_ajaxListener.callback = function () {
    window.location='mpAjaxHandler://' + this.url;
};

XMLHttpRequest.prototype.open = function(a,b) {
  if (!a) var a='';
  if (!b) var b='';
  s_ajaxListener.tempOpen.apply(this, arguments);
  s_ajaxListener.method = a;  
  s_ajaxListener.url = b;
  if (a.toLowerCase() == 'get') {
    s_ajaxListener.data = b.split('?');
    s_ajaxListener.data = s_ajaxListener.data[1];
  }
}

XMLHttpRequest.prototype.send = function(a,b) {
  if (!a) var a='';
  if (!b) var b='';
  s_ajaxListener.tempSend.apply(this, arguments);
  if(s_ajaxListener.method.toLowerCase() == 'post')s_ajaxListener.data = a;
  s_ajaxListener.callback();
}

What this will actually do is change the location of the browser to some made up URL scheme (in this case, mpAjaxHandle) with info about the request made. Don't worry, our delegate with catch this and the location won't change.

UIWebView Delegate

First, we need to read our JavaScript file. I suggest doing storing it in a static variable. I'm in the habit of using +initialize.

static NSString *JSHandler;

+ (void)initialize {
    JSHandler = [[NSString stringWithContentsOfURL:[[NSBundle mainBundle] URLForResource:@"ajax_handler" withExtension:@"js"] encoding:NSUTF8StringEncoding error:nil] retain];
}

Next, we want to inject this JavaScript before a page is done loading so we can receive all events.

- (void)webViewDidStartLoad:(UIWebView *)webView {
    [webView stringByEvaluatingJavaScriptFromString:JSHandler];
}

Finally, we want to capture the event.

Since the URL Scheme is made up, we don't want to actually follow it. We return NO and all is well.

#define CocoaJSHandler          @"mpAjaxHandler"

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
    if ([[[request URL] scheme] isEqual:CocoaJSHandler]) {
        NSString *requestedURLString = [[[request URL] absoluteString] substringFromIndex:[CocoaJSHandler length] + 3];

        NSLog(@"ajax request: %@", requestedURLString);
        return NO;
    }

    return YES;
}

I created a sample project with the solution but have nowhere to host it. You can message me if you can host it and I'll edit this post accordingly.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome to OStack Knowledge Sharing Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...