CAayer - (void)drawInContext:(CGContextRef)ctx 永远不会被调用

Posted 2023-03-13

【中文标题】CAayer - (void)drawInContext:(CGContextRef)ctx 永远不会被调用

【英文标题】：CAayer - (void)drawInContext:(CGContextRef)ctx is never called

【发布时间】：2013-03-09 15:04:00

【问题描述】：

我试图通过子类化使用 CALayer 进行绘制。我知道有一些关于我已经看过其中大部分的帖子并遵循了给出的解决方案但没有成功。比如设置帧大小。这是代码。需要一些帮助提前谢谢

//
//  NewView.m
//  layerPractise


#import "NewView.h"
#import "QuartzCore/QuartzCore.h"
#import "NewLayer.h"
#import "NewLayer2.h"

@interface NewView() 
//  NSMutableArray *_normalizedValues;


@end

@implementation NewView
@synthesize _containerLayer;

@synthesize layer,shouldAddNewLayer;

-(void)doInitialSetup 
    self._containerLayer = [CALayer layer];
    [_containerLayer setFrame:self.frame];
    [self.layer addSublayer:self._containerLayer];
//    [_containerLayer retain];


- (id)initWithFrame:(CGRect)frame

    self = [super initWithFrame:frame];
    if (self) 
        [self doInitialSetup];
    

    return self;


-(id)initWithCoder:(NSCoder *)aDecoder 
    if (self = [super initWithCoder:aDecoder]) 
        [self doInitialSetup];
    

    return self;



- (void)addCustomLayer



    NewLayer *newLayer = [NewLayer layer];

    newLayer.frame = self.bounds;

    [_containerLayer addSublayer:newLayer];
    [newLayer setNeedsDisplay];






// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.

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


@end

和 NewLayer 类

- (id)initWithLayer:(id)layer

    self = [super initWithLayer:layer];
    if (self) 

    

    return self;


- (id)init 
    self = [super init];
    if (self) 

        self.frame = CGRectMake(0, 0, 500, 500);
        self.delegate = self;
        CGRect r = self.frame;
        [self setNeedsDisplay];
    

    return self;


+ (BOOL)needsDisplayForKey:(NSString *)key 

    [super needsDisplayForKey:key];



- (void)drawInContext:(CGContextRef)ctx

    CGContextMoveToPoint(ctx, 100, 100);
    CGContextAddLineToPoint(ctx, 500, 800);
    CGContextSetStrokeColorWithColor(ctx, [UIColor blackColor].CGColor);

    CGContextDrawPath(ctx, kCGPathStroke);

【参考方案1】：

addCustomLayer 方法永远不会被调用。在doInitialSetup 中创建了一个层，但它的类型是CALayer，而不是您的自定义子类NewLayer。