How to detect zoom scale of UIWebView - iphone

Question

I want to increase height of UIWebView while user zoom in (like default mail app in iPhone).
So, I have tried the code below to find scrollview in webview and add UIScrollViewDelegate to use scrollViewDidZoom for detecting zoom scale to increase height of webview on this method.
// MessageAppDelegate.h
#interface MessageAppDelegate : NSObject <UIApplicationDelegate,UIWebViewDelegate,UIScrollViewDelegate> {
UIWebView *webview;
UIScrollView *scrollview;
}
//MessageAppDelegate.m
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{
[self.window makeKeyAndVisible];
webview = [[UIWebView alloc] initWithFrame:CGRectMake(0, 150, 320, 100)];
webview.delegate = self;
webview.scalesPageToFit = YES;
webview.userInteractionEnabled = YES;
[webview loadHTMLString:#"<meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0, maximum-scale=6.0 user-scalable=yes\">test test" baseURL:nil];
[self.window addSubview:webview];
// Find scrollview in webview
for (UIView *view in webview.subviews) {
if ([view isKindOfClass:[UIScrollView class]]) {
// Get UIScrollView object
scrollview = (UIScrollView *) view;
scrollview.delegate = self;
}
}
return YES;
}
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale{
NSLog(#"scale %f",scale);
}
- (void)scrollViewDidZoom:(UIScrollView *)scrollView{
NSLog(#"scrollViewDidZoom %f",scrollview.zoomScale);
}
The problem is I cannot zoom in/out on the webview
but NSLog on scrollViewDisEndZooming method showed
scale 1.0
when I ended zooming
and scrollViewDidZoom method didn't show anything.
I want to detect zoom scale of webview for calculating its height on scrollViewDidZoom.
What I've done wrong?
Please help.
Thanks in advance.

Answer 1

I have done well for your code up,do following modificaitons:
you just get the scrollview class point ,then can get the scrollview.contentSize.width,which can change when you zoom in out,but scrollview.zoomScale always remains 1.so have to use contensize.width to calculate scale.
#interface dictViewController : UIViewController<UIWebViewDelegate,UITextFieldDelegate,UIGestureRecognizerDelegate,UIScrollViewDelegate>{
UIScrollView *scrollview;
......................
//scrollview.delegate = self;
for (UIView *view in webViewM.subviews) {
if ([view isKindOfClass:[UIScrollView class]]) {
// Get UIScrollView object
scrollview = (UIScrollView *) view;
//scrollview.delegate = self;
}
}
/*
- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale{
//NSLog(#"scale zooming %f",scale);
}
- (void)scrollViewDidZoom:(UIScrollView *)scrollView{
//NSLog(#"scrollViewDidZoom %f",scrollview.zoomScale);
}*/
- (void)swipeRightAction:(id)ignored
{
NSLog(#"wid=%f", scrollview.contentSize.width);
NSLog(#"zoomscale=%f", scrollview.zoomScale);
}

Answer 2

I don't think there's a proper way to do it from the exposed APIs, but there is a hacky way.
A UIWebView contains a UIScrollView which can be given a delegate. Then when zooming changes, you (the delegate) get a callback called scrollViewDidZoom:.
In order to find the scroll view, you can get the subviews collection from the web view and iterate to see which one isKindOfClass:[UIScrollView class].
Now, UIWebView also conforms to UIScrollViewDelegate. So that may mean you are changing the web view's implementation, and that could be a Bad Idea. Test well.