Iphone – How to get the current zoom level in a UIScrollView

centeriphoneuiscrollviewzooming

In an attempt to create a workaround for centering an image in a UIScrollView and make it behave as Apple's Photos app does, I need to get the current zoom level and use the number to calculate the amount the image should be inset at each zoom level.

(Note: I am aware that some programmers are centering an image in a scrollview by centering the image in a UIView that is the same size as the scrollview. This does not give good results and I am trying to find out how apple made it work in the photos app.)

So, anyone know how to get the current zoom level of the content in a UIScrollView?

Best Answer

Yep I got your problem's answer. I think you should use this method in your scrollViewController Class.

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale{
    NSLog(@"Zoomscale %f",scale);
        NSLog(@"Zoom End!");
}

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];
}

R – How to make a UIScrollView zoom to size of UIImage

I tracked down the sample code you were pulling from. It was the TapToZoom project in the ScrollViewSuite available at http://developer.apple.com/iphone.

I changed the line that calculates the newScale to be the ratio between the size of Scroll View's frame, and the size of the Image View's Image. This has the effect you desire of zooming-in until the image is shown at 1:1 resolution.

Note: I also had make sure the UIImageView named imageView was a class variable. In the original sample code, it was declared locally in the viewDidLoad: method.

The caveat here is that the scroll view and the image have the same x/y ratio. I ony did math on the width.

- (void)tapDetectingImageView:(TapDetectingImageView *)view gotDoubleTapAtPoint:(CGPoint)tapPoint {
    // double tap zooms in on them image to a 1:1 resolution (based on width)
    float newScale =  imageView.image.size.width / imageScrollView.frame.size.width;
    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:tapPoint];
    [imageScrollView zoomToRect:zoomRect animated:YES];
}

Best Answer

Related Solutions

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

R – How to make a UIScrollView zoom to size of UIImage

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