UIWebView 使用要注意的几点

UIWebView 使用要注意的几点

最近有客户希望将移动端统一使用HTML5来完成，在iOS端就要用到UIWebView。遇到了以下三个主要问题：

加载HTTPS页面

不像Safari可以弹出弹框问用户是否忽略证书，在UIWebView中只会得到一个空白页。由于UIWebView并没有提供HTTPS相关的接口，所以不能直接在UIWebView中进行操作。经过stackoverflow知道，原来可以先通过NSURLConnection通过HTTPS验证，然后再用UIWebView加载页面，这样就达到了想要的目的。

#pragma mark - Webview delegate

- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType;
{
    NSLog(@"Did start loading: %@ auth:%d", [[request URL] absoluteString], _authenticated);

    if (!_authenticated) {
        _authenticated = NO;

        _urlConnection = [[NSURLCoNnection alloc] initWithRequest:_request delegate:self];

        [_urlConnection start];

        return NO;
    }

    return YES;
}

#pragma mark - NURLConnection delegate

- (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge;
{
    NSLog(@"WebController Got auth challange via NSURLConnection");

    if ([challenge previousFailureCount] == 0)
    {
        _authenticated = YES;

        NSURLCredential *credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];

        [challenge.sender useCredential:credential forAuthenticationChallenge:challenge];

    } else
    {
        [[challenge sender] cancelAuthenticationChallenge:challenge];
    }
}

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
{
    NSLog(@"WebController received response via NSURLConnection");

    // remake a webview call now that authentication has passed ok.
    _authenticated = YES;

    [_web loadRequest:_request];

    // Cancel the URL connection otherwise we double up (webview + url connection, same url = no good!)
    [_urlConnection cancel];
}

// We use this method is to accept an untrusted site which unfortunately we need to do, as our PVM servers are self signed.
- (BOOL)connection:(NSURLConnection *)connection canAuthenticateAgainstProtectionSpace:(NSURLProtectionSpace *)protectionSpace
{
    return [protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust];
}

中文乱码

由于服务器端使用的编码是GBK，UIWebView默认的是UTF-8编码，导致加载时出现乱码。将UIWebView的loadRequest方法用loadData方法来代替，具体代码如下：

NSURL *url = [NSURL URLWithString:_address.text];
NSData *data = [NSData dataWithContentsOfURL:url];
[_web loadData:data MIMEType:@"text/html" textEncodingName:@"GBK" baseURL:url];

旋转自适应

当iOS设备从Portrait旋转为Landscape时，UIWebView的宽度只占屏幕的一半。发现是autoResize的相关参数没有进行设置，应该设置如下：

webview.scalesPageToFit = YES;
webview.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

又由于不同的Orientation，其缩放参数不一样，所以在旋转时应对scrollView的zoomScale进行设置，如下：

- (void)willRotateToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {

    NSLog(@"willRotateToInterfaceOrientation");

    CGFloat ratioAspect = _web.bounds.size.width/_web.bounds.size.height;
    switch (toInterfaceOrientation) {
        case UIInterfaceOrientationPortraitUpsideDown:
        case UIInterfaceOrientationPortrait:
            // Going to Portrait mode
            NSLog(@"Portrait mode");
            for (UIScrollView *scroll in [_web subviews]) { //we get the scrollview
                // Make sure it really is a scroll view and reset the zoom scale.
                if ([scroll respondsToSelector:@selector(setZoomScale:)]){
                    scroll.minimumZoomScale = scroll.minimumZoomScale/ratioAspect;
                    scroll.maximumZoomScale = scroll.maximumZoomScale/ratioAspect;
                    [scroll setZoomScale:(scroll.zoomScale/ratioAspect) animated:YES];
                }
            }
            break;
        default:
            // Going to Landscape mode
            NSLog(@"Landscape mode");
            for (UIScrollView *scroll in [_web subviews]) { //we get the scrollview
                // Make sure it really is a scroll view and reset the zoom scale.
                if ([scroll respondsToSelector:@selector(setZoomScale:)]){
                    scroll.minimumZoomScale = scroll.minimumZoomScale *ratioAspect;
                    scroll.maximumZoomScale = scroll.maximumZoomScale *ratioAspect;
                    [scroll setZoomScale:(scroll.zoomScale*ratioAspect) animated:YES];
                }
            }
            break;
    }
}