Iphone – How to detect zoom scale of UIWebView

iphoneuiscrollviewuiwebviewzooming

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.

Best Answer

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);

}

Related Solutions

Ios – How to make a UITextField move up when the keyboard is present – on starting to edit

You will only need a ScrollView if the contents you have now do not fit in the iPhone screen. (If you are adding the ScrollView as the superview of the components just to make the TextField scroll up when keyboard comes up, then it's not needed.)
The standard way to prevent the TextFields from being covered by the keyboard is to move the view up/down whenever the keyboard is shown.

Here is some sample code:

#define kOFFSET_FOR_KEYBOARD 80.0

-(void)keyboardWillShow {
    // Animate the current view out of the way
    if (self.view.frame.origin.y >= 0)
    {
        [self setViewMovedUp:YES];
    }
    else if (self.view.frame.origin.y < 0)
    {
        [self setViewMovedUp:NO];
    }
}

-(void)keyboardWillHide {
    if (self.view.frame.origin.y >= 0)
    {
        [self setViewMovedUp:YES];
    }
    else if (self.view.frame.origin.y < 0)
    {
        [self setViewMovedUp:NO];
    }
}

-(void)textFieldDidBeginEditing:(UITextField *)sender
{
    if ([sender isEqual:mailTf])
    {
        //move the main view, so that the keyboard does not hide it.
        if  (self.view.frame.origin.y >= 0)
        {
            [self setViewMovedUp:YES];
        }
    }
}

//method to move the view up/down whenever the keyboard is shown/dismissed
-(void)setViewMovedUp:(BOOL)movedUp
{
    [UIView beginAnimations:nil context:NULL];
    [UIView setAnimationDuration:0.3]; // if you want to slide up the view

    CGRect rect = self.view.frame;
    if (movedUp)
    {
        // 1. move the view's origin up so that the text field that will be hidden come above the keyboard 
        // 2. increase the size of the view so that the area behind the keyboard is covered up.
        rect.origin.y -= kOFFSET_FOR_KEYBOARD;
        rect.size.height += kOFFSET_FOR_KEYBOARD;
    }
    else
    {
        // revert back to the normal state.
        rect.origin.y += kOFFSET_FOR_KEYBOARD;
        rect.size.height -= kOFFSET_FOR_KEYBOARD;
    }
    self.view.frame = rect;

    [UIView commitAnimations];
}


- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    // register for keyboard notifications
    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillShow)
                                             name:UIKeyboardWillShowNotification
                                           object:nil];

    [[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(keyboardWillHide)
                                             name:UIKeyboardWillHideNotification
                                           object:nil];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    // unregister for keyboard notifications while not visible.
    [[NSNotificationCenter defaultCenter] removeObserver:self
                                             name:UIKeyboardWillShowNotification
                                           object:nil];

    [[NSNotificationCenter defaultCenter] removeObserver:self
                                             name:UIKeyboardWillHideNotification
                                           object:nil];
}

Javascript – How to detect page zoom level in all modern browsers

Now it's an even bigger mess than it was when this question was first asked. From reading all the responses and blog posts I could find, here's a summary. I also set up this page to test all these methods of measuring the zoom level.

Edit (2011-12-12): I've added a project that can be cloned: https://github.com/tombigel/detect-zoom

IE8: screen.deviceXDPI / screen.logicalXDPI (or, for the zoom level relative to default zoom, screen.systemXDPI / screen.logicalXDPI)
IE7: var body = document.body,r = body.getBoundingClientRect(); return (r.left-r.right)/body.offsetWidth; (thanks to this example or this answer)
FF3.5 ONLY: screen.width / media query screen width (see below) (takes advantage of the fact that screen.width uses device pixels but MQ width uses CSS pixels--thanks to Quirksmode widths)
FF3.6: no known method
FF4+: media queries binary search (see below)
WebKit: https://www.chromestatus.com/feature/5737866978131968 (thanks to Teo in the comments)
WebKit: measure the preferred size of a div with -webkit-text-size-adjust:none.
WebKit: (broken since r72591) document.width / jQuery(document).width() (thanks to Dirk van Oosterbosch above). To get ratio in terms of device pixels (instead of relative to default zoom), multiply by window.devicePixelRatio.
Old WebKit? (unverified): parseInt(getComputedStyle(document.documentElement,null).width) / document.documentElement.clientWidth (from this answer)
Opera: document.documentElement.offsetWidth / width of a position:fixed; width:100% div. from here (Quirksmode's widths table says it's a bug; innerWidth should be CSS px). We use the position:fixed element to get the width of the viewport including the space where the scrollbars are; document.documentElement.clientWidth excludes this width. This is broken since sometime in 2011; I know no way to get the zoom level in Opera anymore.
Other: Flash solution from Sebastian
Unreliable: listen to mouse events and measure change in screenX / change in clientX

Here's a binary search for Firefox 4, since I don't know of any variable where it is exposed:

<style id=binarysearch></style>
<div id=dummyElement>Dummy element to test media queries.</div>
<script>
var mediaQueryMatches = function(property, r) {
  var style = document.getElementById('binarysearch');
  var dummyElement = document.getElementById('dummyElement');
  style.sheet.insertRule('@media (' + property + ':' + r +
                         ') {#dummyElement ' +
                         '{text-decoration: underline} }', 0);
  var matched = getComputedStyle(dummyElement, null).textDecoration
      == 'underline';
  style.sheet.deleteRule(0);
  return matched;
};
var mediaQueryBinarySearch = function(
    property, unit, a, b, maxIter, epsilon) {
  var mid = (a + b)/2;
  if (maxIter == 0 || b - a < epsilon) return mid;
  if (mediaQueryMatches(property, mid + unit)) {
    return mediaQueryBinarySearch(
        property, unit, mid, b, maxIter-1, epsilon);
  } else {
    return mediaQueryBinarySearch(
        property, unit, a, mid, maxIter-1, epsilon);
  }
};
var mozDevicePixelRatio = mediaQueryBinarySearch(
    'min--moz-device-pixel-ratio', '', a, b, maxIter, epsilon);
var ff35DevicePixelRatio = screen.width / mediaQueryBinarySearch(
    'min-device-width', 'px', 0, 6000, 25, .0001);
</script>

Best Answer

Related Solutions

Ios – How to make a UITextField move up when the keyboard is present – on starting to edit

Javascript – How to detect page zoom level in all modern browsers

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