为什么我的 CATiledLayer 在缩放后不会在 UIScrollView 中滚动？

Question

我目前在使用 CATiledLayer 时遇到以下问题：当视图首次加载时，滚动效果很好，但是当您缩放一次时，视图会捕捉到锚点（左上角）并且无法再滚动一点也不。缩放的工作原理是它会放大和缩小，但它只会放大到左上角。

我的代码如下：

#import <QuartzCore/QuartzCore.h>
#import "PracticeViewController.h"

@implementation practiceViewController
//@synthesize image;

- (void)viewDidLoad
{


    NSString *path = [[NSBundle mainBundle] pathForResource:@"H-5" ofType:@"jpg"]; 
    NSData *data = [NSData dataWithContentsOfFile:path];
    image = [UIImage imageWithData:data];

    CGRect pageRect = CGRectMake(0,  0,  image.size.width, image.size.height);  


    CATiledLayer *tiledLayer = [CATiledLayer layer];
    tiledLayer.anchorPoint = CGPointMake(0.0f, 1.0f);
    tiledLayer.delegate = self;
    tiledLayer.tileSize = CGSizeMake(1000, 1000);
    tiledLayer.levelsOfDetail = 6; 
    tiledLayer.levelsOfDetailBias = 0;
    tiledLayer.bounds = pageRect; 
    tiledLayer.transform = CATransform3DMakeScale(1.0f, -1.0f, 0.3f);

    myContentView = [[UIView alloc] initWithFrame:self.view.bounds];
    [myContentView.layer addSublayer:tiledLayer];

    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
    scrollView.delegate = self;
    scrollView.contentSize = pageRect.size;
    scrollView.minimumZoomScale = .2;   
    scrollView.maximumZoomScale = 1; 
    [scrollView addSubview:myContentView];
    [self.view addSubview:scrollView];


}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return myContentView;
}

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx
{
    NSString *path = [[NSBundle mainBundle] pathForResource:@"H-5" ofType:@"jpg"]; 
    NSData *data = [NSData dataWithContentsOfFile:path];
    image = [UIImage imageWithData:data];

    CGRect imageRect = CGRectMake (0.0, 0.0, image.size.width, image.size.height);
    CGContextDrawImage (ctx, imageRect, [image CGImage]);
}

@end

Answer 1

这是我修复明显错误的第一步：

#import <QuartzCore/QuartzCore.h>
#import "PracticeViewController.h"

@implementation PracticeViewController
@synthesize image;

- (void)viewDidLoad
{
    [super viewDidLoad];

    // You do not need to and must not autorelease [NSBundle mainBundle]
    NSString *path = [[NSBundle mainBundle] pathForResource:@"H-5" ofType:@"jpg"]; 
    NSData *data = [NSData dataWithContentsOfFile:path];
    image = [UIImage imageWithData:data];

    CGRect pageRect = CGRectMake(0,  0,  1600, 2400);

    CATiledLayer *tiledLayer = [CATiledLayer layer];
    tiledLayer.delegate = self;
    tiledLayer.tileSize = CGSizeMake(1024.0, 1024.0);
    tiledLayer.levelsOfDetail = 5; // was 1000, which makes no sense. Each level of detail is a power of 2.
    tiledLayer.levelsOfDetailBias = 0; // was 1000, which also makes no sense. 
    // Do not change the tiledLayer.frame.
    tiledLayer.bounds = pageRect; // I think you meant bounds instead of frame.
    // Flip the image vertically.
    tiledLayer.transform = CATransform3DMakeScale(zoom, -zoom, 1.0f);

    myContentView = [[UIView alloc] initWithFrame:self.view.bounds];
    [myContentView.layer addSublayer:tiledLayer];

    UIScrollView *scrollView = [[UIScrollView alloc] initWithFrame:self.view.bounds];
    scrollView.delegate = self;
    scrollView.contentSize = pageRect.size;
    scrollView.maximumZoomScale = 32; // = 2 ^ 5
    [scrollView addSubview:myContentView];

    [self.view addSubview:scrollView];
}

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView
{
    return myContentView;
}

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx
{
    NSString *path = [[NSBundle mainBundle] pathForResource:@"H-5" ofType:@"jpg"]; 
    NSData *data = [NSData dataWithContentsOfFile:path];
    image = [UIImage imageWithData:data];
    CGRect imageRect = CGRectMake (0.0, 0.0, image.size.width, image.size.height);
    CGContextDrawImage (context, imageRect, [image CGImage]);
}

@end