未调用CATiledlayer委托

Question

我正在尝试使用一个单独的委托类(就像许多示例一样)在CATiledlayer中执行大图像的绘制。平铺图层已添加为单独视图中的子图层。我首先从一个视图控制器开始。

//  ImageInTiledLayerViewController.h

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
#import "MyView.h"
#import "MyDelegate.h"

@interface ImageInTiledLayerViewController : UIViewController {
    MyView *myView;
    MyDelegate *myDelegate;
    CATiledLayer *tiledLayer;
}

@property (nonatomic, retain) MyView *myView;
@property (nonatomic, retain) MyDelegate *myDelegate;
@property (nonatomic, retain) CATiledLayer *tiledLayer;

@end

//  ImageInTiledLayerViewController.m

#import "ImageInTiledLayerViewController.h"

@implementation ImageInTiledLayerViewController

@synthesize myView;
@synthesize myDelegate;
@synthesize tiledLayer;

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {
    [super viewDidLoad];

    // create the view
    myView = [[MyView alloc] initWithFrame:CGRectMake(0.0, 0.0, 1200.0, 800.0)];
    myView.backgroundColor = [UIColor whiteColor];

    // delegate for the titled layer
    myDelegate = [[MyDelegate alloc] init];

    // create the tiled layer
    tiledLayer = [CATiledLayer layer];
    tiledLayer.frame = CGRectMake(0.0, 0.0, 1200.0, 800.0);

    // set the tiled layers delegate for drawing
    tiledLayer.delegate = myDelegate;

    // add the tiled layer to the view
    [myView.layer addSublayer:tiledLayer];

    // add the view to this controllers view
    [self.view addSubview:myView];

    // tile layer needs layout
    [tiledLayer setNeedsLayout];
}

- (void)dealloc {
    [super dealloc];
}

@end

我的观点目前只是一个基本观点。我想把它放在视图中，因为我稍后会把它添加到滚动视图中，它会对触摸事件做出响应。

//  MyView.h

#import <UIKit/UIKit.h>


@interface MyView : UIView {

}

@end

//  MyView.m

#import "MyView.h"


@implementation MyView


- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
        // Initialization code
    }
    return self;
}


- (void)drawRect:(CGRect)rect {
    // Drawing code
}


- (void)dealloc {
    [super dealloc];
}


@end

这就是问题所在。

//  MyDelegate.h

#import <Foundation/Foundation.h>


@interface MyDelegate : NSObject {
    CGImageRef myImageRef;
}

@property (nonatomic) CGImageRef myImageRef;

@end


//  MyDelegate.m

#import "MyDelegate.h"


@implementation MyDelegate

@synthesize myImageRef;

- (id)init {
    // assign the image reference
    myImageRef = [UIImage imageNamed:@"Waterfall.png"].CGImage; 
    return self;
}
// THIS NEVER GETS CALLED
-(void)drawLayer:(CALayer*)layer inContext:(CGContextRef)context {
    // re-orientate the context
    CGContextTranslateCTM(context, 0.0, CGImageGetHeight(myImageRef));
    CGContextScaleCTM(context, 1.0, -1.0);  
    CGContextDrawImage(context, CGRectMake(0.0, 0.0, CGImageGetWidth(myImageRef), CGImageGetHeight(myImageRef)), myImageRef);
}

@end

尽管我为tile层调用了setNeedsLayout，但从未调用过drawLayer方法，因此也从未绘制过图像。

Answer 1

在你的委托的init方法中，你也错过了对super的调用：

if (self = [super init]) {
    // ...
}

Answer 2

你正在重画CATiledLayer，用这个代替，你应该是golen。

-(void)drawLayer:(CATiledLayer*)layer inContext:(CGContextRef)context {
    // re-orientate the context
    CGContextTranslateCTM(context, 0.0, CGImageGetHeight(myImageRef));
    CGContextScaleCTM(context, 1.0, -1.0);      
    CGContextDrawImage(context, CGRectMake(0.0, 0.0, CGImageGetWidth(myImageRef), CGImageGetHeight(myImageRef)), myImageRef);
}