how does one check if UIWebView is empty or not

问题

I need to check if a webview when completed loading has any content or not.

What I require is simple. Its a small webview strip at the bottom of my pages (like an advert)

I call

NSURLRequest *request=[NSURLRequest requestWithURL:adURL];
[gWebView loadRequest:request];

I get the callback

-(void)webViewDidFinishLoad:(UIWebView *)webView {

But in my scenario the webview shall return empty and sometime it shall have data.

I do not want to show the webview if my server php file returned nothing.

How can I verify that I received an empty page in the callback (or any other way)?

回答1:

If you are loading a HTML page:

NSString *string = [myWebView stringByEvaluatingJavaScriptFromString:@"document.getElementsByTagName('html')[0].innerHTML"];
BOOL isEmpty = string==nil || [string length]==0;

Or you could load the content first, test if it is not empty, and then feed it to the webview. See UIWebView's loadHTMLString:baseURL: or loadData:MIMEType:textEncodingName:baseURL:.

回答2:

This is based on Jano's approach but should perform better:

NSString *script = @"document.getElementsByTagName('body')[0].innerHTML.length";
NSString *length = [self.webView stringByEvaluatingJavaScriptFromString:script];

if (length.integerValue > 0) {
    NSLog(@"not empty");
}

回答3:

Just replying to an old post, but maybe new arrivals will find it useful. I struggled with the same problem and found this solution to work in my case:

if (webView.request.URL.absoluteURL == nil) {
        NSLog(@"nil webby");
        NSLog(@"url: %@", webView.request.URL.absoluteURL);
        // Perform some task when the url is nil
    } else {
        NSLog(@"loaded webby");
        NSLog(@"url: %@", webView.request.URL.absoluteURL);
        // Perform some task when the url is loaded
}

You can call it from the webViewDidFinishLoad: method.

回答4:

In my case, I was looking to detect if the PDF was malformed. I.e., the web view would be empty because the PDF could not be loaded. Since with iOS 7.1.1, I wasn't getting the didFailLoadWithError delegate callback, I needed a different way to do this. I ended up using the method below before attempting to load the PDF doc into the web view.

// See https://developer.apple.com/library/ios/documentation/graphicsimaging/conceptual/drawingwithquartz2d/dq_pdf/dq_pdf.html
- (BOOL) isValidPDFDoc: (NSURL *) deviceLocalURL {
    CFStringRef path;
    CFURLRef url;
    CGPDFDocumentRef document;
    size_t count;
    BOOL validDocument = YES;

    // Must use path of URL not absoluteString here.
    path = CFStringCreateWithCString (NULL, [[deviceLocalURL path] cStringUsingEncoding:NSASCIIStringEncoding],
                                      kCFStringEncodingUTF8);
    url = CFURLCreateWithFileSystemPath (NULL, path, // 1
                                         kCFURLPOSIXPathStyle, 0);
    CFRelease (path);
    document = CGPDFDocumentCreateWithURL (url);// 2
    if (!document) {
        validDocument = NO;
    }

    CFRelease(url);
    count = CGPDFDocumentGetNumberOfPages (document);// 3
    if (count == 0) {
        validDocument = NO;
    }

    CGPDFDocumentRelease (document);

    return validDocument;
}

来源：https://stackoverflow.com/questions/7581909/how-does-one-check-if-uiwebview-is-empty-or-not

标签

ios

uiwebview

uiwebviewdelegate