UIImage Is Not Fitting In UIScrollView At Start

问题:

I have an image like:

When I load the image to uiimageview and then adding as a subview to uiscrollview, at start the image is showing like:

The problem is I want to see all the image fit to screen at start but it is showing already zoomed. Is there a way to handle this please help ...

I have the code like:

[self.view addSubview:scrollView];
UIImageView *tempImageView = 
[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Tree.jpg"]];
self.imageView = tempImageView;
[tempImageView release];
[scrollView setContentMode:UIViewContentModeScaleAspectFit];
[imageView sizeToFit];
scrollView.backgroundColor=[UIColor blackColor];
scrollView.contentSize = imageView.frame.size;
scrollView.minimumZoomScale = scrollView.frame.size.width / imageView.frame.size.width;
scrollView.maximumZoomScale = 4.0;
[scrollView setZoomScale:1.0];
scrollView.clipsToBounds = YES;
scrollView.delegate = self;
[scrollView addSubview:imageView];

回答1:

Probably you are looking for this,

UIImageView *tempImageView = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Watson.jpg"]] autorelease];
tempImageView.frame = scrollView.bounds;
self.imageView = tempImageView;

scrollView.backgroundColor = [UIColor blackColor];
scrollView.minimumZoomScale = 1.0  ;
scrollView.maximumZoomScale = imageView.image.size.width / scrollView.frame.size.width;
scrollView.zoomScale = 1.0;
scrollView.delegate = self;

[scrollView addSubview:imageView];

回答2:

Have a look at the contentMode-Property of UIView (UIImageView also supports this).

imageView.contentMode = UIViewContentModeScaleAspectFit;

This should work...

回答3:

I think the problem is in

UIImageView *tempImageView = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"Tree.jpg"]];

Apple's docs say "This method adjusts the frame of the receiver to match the size of the specified image. It also disables user interactions for the image view by default."
instead use

UIImageView *tempImageView = [[UIImageView alloc] initWithFrame:CGRectMake(0,0,320,480)];
tempImageView.image = [UIImage imageNamed:@"Tree.jpg"];

回答4:

Note that there is also [scrollView zoomToRect:animated:] described here

You can set it to the outer bounds of your image so that it will auto-fit your image in your view. But make sure to setup correctly the maximumZoomScale as per Deepak solution above.

回答5:

I used Deepak's solution and Apples recommendations and subclassed UIScrollView with UIImageView inside it. However, I zoom the image only on first layout of my scrollview subclass and only if frame size is smaller than image size:

- (void)layoutSubviews
{
[super layoutSubviews];

// center the image as it becomes smaller than the size of the screen
CGSize boundsSize = self.bounds.size;
CGRect frameToCenter = _imageView.frame;

// center horizontally
if (frameToCenter.size.width < boundsSize.width)
    frameToCenter.origin.x = (boundsSize.width - frameToCenter.size.width) / 2;
else
    frameToCenter.origin.x = 0;

// center vertically
if (frameToCenter.size.height < boundsSize.height)
    frameToCenter.origin.y = (boundsSize.height - frameToCenter.size.height) / 2;
else
    frameToCenter.origin.y = 0;

_imageView.frame = frameToCenter;

// If image is bigger than frame, we zoom it on first load (zoom value is smaller than 1.0)
if (_firstLayout) {
    _firstLayout = NO;
    self.zoomScale = (self.frame.size.width < _imageView.image.size.width) ? (self.frame.size.width / _imageView.image.size.width) : 1.0;
}
}

This is how I init my subclass:

- (id)initWithFrame:(CGRect)frame image:(UIImage*)image
{
self = [super initWithFrame:frame];
if (self) {

    _firstLayout = YES;

    _imageView = [[UIImageView alloc] initWithImage:image];
    [self addSubview:_imageView];

    self.backgroundColor = [UIColor blackColor];
    self.minimumZoomScale = 0.1;
    self.maximumZoomScale = 10;


    self.delegate = self;
}
return self;
}