我正在尝试将图像加载到滚动视图中并将手势识别器添加到图像中，以便可以放大和滚动。但不知何故，我无法让这个工作。我已经使用 xib 文件构建了应用程序。起初我将滚动视图放在 xib 文件中的视图顶部，但因为它没有成功（给了我一个空白的黑屏）然后我尝试以编程方式将滚动视图放在 .m 文件上。但现在它给了我一个空白的白色屏幕。我正在使用 SDWebImage 下载图像。这是我的代码：
#import "ZoomAndPanViewController.h"
#import "UIImageView+WebCache.h"
@interface ZoomAndPanViewController ()
@property (nonatomic, strong) UIImageView *imageView;
@property (nonatomic, strong) UIImage *image;
- (void)centerScrollViewContents;
- (void)scrollViewDoubleTapped:(UITapGestureRecognizer*)recognizer;
- (void)scrollViewTwoFingerTapped:(UITapGestureRecognizer*)recognizer;
@end
@implementation ZoomAndPanViewController
@synthesize scrollView = _scrollView;
@synthesize imageView = _imageView;
- (void)centerScrollViewContents {
CGSize boundsSize = self.scrollView.bounds.size;
CGRect contentsFrame = self.imageView.frame;
if (contentsFrame.size.width < boundsSize.width) {
contentsFrame.origin.x = (boundsSize.width - contentsFrame.size.width) / 2.0f;
} else {
contentsFrame.origin.x = 0.0f;
}
if (contentsFrame.size.height < boundsSize.height) {
contentsFrame.origin.y = (boundsSize.height - contentsFrame.size.height) / 2.0f;
} else {
contentsFrame.origin.y = 0.0f;
}
self.imageView.frame = contentsFrame;
}
- (void)scrollViewDoubleTapped:(UITapGestureRecognizer*)recognizer {
// Get the location within the image view where we tapped
CGPoint pointInView = [recognizer locationInView:self.imageView];
// Get a zoom scale that's zoomed in slightly, capped at the maximum zoom scale specified by the scroll view
CGFloat newZoomScale = self.scrollView.zoomScale * 1.5f;
newZoomScale = MIN(newZoomScale, self.scrollView.maximumZoomScale);
// Figure out the rect we want to zoom to, then zoom to it
CGSize scrollViewSize = self.scrollView.bounds.size;
CGFloat w = scrollViewSize.width / newZoomScale;
CGFloat h = scrollViewSize.height / newZoomScale;
CGFloat x = pointInView.x - (w / 2.0f);
CGFloat y = pointInView.y - (h / 2.0f);
CGRect rectToZoomTo = CGRectMake(x, y, w, h);
[self.scrollView zoomToRect:rectToZoomTo animated:YES];
}
- (void)scrollViewTwoFingerTapped:(UITapGestureRecognizer*)recognizer {
// Zoom out slightly, capping at the minimum zoom scale specified by the scroll view
CGFloat newZoomScale = self.scrollView.zoomScale / 1.5f;
newZoomScale = MAX(newZoomScale, self.scrollView.minimumZoomScale);
[self.scrollView setZoomScale:newZoomScale animated:YES];
}
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
CGRect scrollFrame = [[UIScreen mainScreen]applicationFrame];
self.scrollView = [[UIScrollView alloc]initWithFrame:scrollFrame];
self.scrollView.delegate = self;
// Set a nice title
self.title = @"Image";
self.imageView = [[UIImageView alloc] init];
self.image = [[UIImage alloc]init];
__block UIActivityIndicatorView *activityIndicator;
[self.imageView setImageWithURL:[NSURL URLWithString:@"http://blablabla"] placeholderImage:nil options:SDWebImageProgressiveDownload progress:^(NSUInteger receivedSize, long long expectedSize)
{
if (!activityIndicator)
{
NSLog(@"setting up the indicator");
[self.imageView addSubview:activityIndicator = [UIActivityIndicatorView.alloc initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleGray]];
activityIndicator.center = self.imageView.center;
[activityIndicator startAnimating];
NSLog(@"indicator start animating");
}
}
completed:^(UIImage *uiimage, NSError *error, SDImageCacheType cacheType)
{
NSLog(@"download image completed");
[activityIndicator removeFromSuperview];
activityIndicator = nil;
self.image = uiimage;
[self.imageView setImage:self.image];
NSLog(@"image vs uiimage : %f x %f vs %f vs %f", self.image.size.width, self.image.size.height, uiimage.size.width, uiimage.size.height);
}];
// Set up the image we want to scroll & zoom and add it to the scroll view
self.imageView.frame = (CGRect){.origin=CGPointMake(0.0f, 0.0f), .size=self.image.size};
[self.scrollView addSubview:self.imageView];
// Tell the scroll view the size of the contents
self.scrollView.contentSize = self.image.size;
NSLog(@"scrollview contentsize %f x %f", self.image.size.width, self.scrollView.contentSize.height);
UITapGestureRecognizer *doubleTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(scrollViewDoubleTapped:)];
doubleTapRecognizer.numberOfTapsRequired = 2;
doubleTapRecognizer.numberOfTouchesRequired = 1;
[self.scrollView addGestureRecognizer:doubleTapRecognizer];
UITapGestureRecognizer *twoFingerTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(scrollViewTwoFingerTapped:)];
twoFingerTapRecognizer.numberOfTapsRequired = 1;
twoFingerTapRecognizer.numberOfTouchesRequired = 2;
[self.scrollView addGestureRecognizer:twoFingerTapRecognizer];
//[self.view addSubview:self.scrollView];
[SDWebImageManager.sharedManager.imageDownloader setValue:@"SDWebImage Demo" forHTTPHeaderField:@"AppName"];
SDWebImageManager.sharedManager.imageDownloader.queueMode = SDWebImageDownloaderLIFOQueueMode;
}
- (void)viewDidUnload
{
[super viewDidUnload];
// Release any retained subviews of the main view.
}
- (void)viewWillAppear:(BOOL)animated {
[super viewWillAppear:animated];
// Set up the minimum & maximum zoom scales
CGRect scrollViewFrame = self.scrollView.frame;
CGFloat scaleWidth = scrollViewFrame.size.width / self.scrollView.contentSize.width;
CGFloat scaleHeight = scrollViewFrame.size.height / self.scrollView.contentSize.height;
CGFloat minScale = MIN(scaleWidth, scaleHeight);
self.scrollView.minimumZoomScale = minScale;
self.scrollView.maximumZoomScale = 1.0f;
self.scrollView.zoomScale = minScale;
[self centerScrollViewContents];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return (interfaceOrientation != UIInterfaceOrientationPortraitUpsideDown);
}
- (UIView*)viewForZoomingInScrollView:(UIScrollView *)scrollView {
// Return the view that we want to zoom
return self.imageView;
}
- (void)scrollViewDidZoom:(UIScrollView *)scrollView {
// The scroll view has zoomed, so we need to re-center the contents
[self centerScrollViewContents];
}
@end
任何关于我在代码中做错的线索和任何帮助都将不胜感激。
谢谢！