UI视图相关

1.事件传递及相应

(1)UIView及CALayer

截图1.png

UIView为其提供内容，以及负责触摸等事件，参与视图事件相应链。
CALayer负责显示内容contents

(2)事件传递及视图相应链

截图2.png

a.事件传递

 - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event;
 - (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event;

事件传递的流程

截图3.png

hitTest:withEvent:系统实现

截图4.png

代码实战
方形按钮指定区域接受事件相应

截图5.png

#import 

@interface CustomButton : UIButton

@end
#import "CustomButton.h"

@implementation CustomButton

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event{
    if (!self.userInteractionEnabled || [self isHidden] || self.alpha <= 0.01) {
        return nil;
    }
    if ([self pointInside:point withEvent:event]) {
        //遍历当前对象的子视图
        __block UIView *hit = nil;
        [self.subviews enumerateObjectsUsingBlock:^(__kindof UIView * _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
            CGPoint vonvertPoint = [self convertPoint:point toView:obj];
            //调用子视图的hittest方法
            hit = [obj hitTest:vonvertPoint withEvent:event];
            //如果找到了接受事件的对象，则停止遍历
            if (hit) {
                *stop = YES;
            }
        }];
        if (hit) {
            return hit;
        }else{
            return self;
        }
    }else{
        return nil;
    }
}
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
    CGFloat x1 = point.x;
    CGFloat y1 = point.y;
  
    CGFloat x2 = self.frame.size.width/2;
    CGFloat y2 = self.frame.size.height/2;
    
    double dis = sqrt((x1-x2) * (x1-x2) + (y1-y2) * (y1-y2));
    
    //以当前控件中心为圆心半径为当前控件宽度的圆内
    if (dis <= self.frame.size.width/2) {
        return YES;
    }else{
       return NO;
    }
}
@end

b.事件相应

截图6.png

视图相应事件

- (void)touchesBegan:(NSSet *)touches withEvent:(nullable UIEvent *)event;
- (void)touchesMoved:(NSSet *)touches withEvent:(nullable UIEvent *)event;
- (void)touchesEnded:(NSSet *)touches withEvent:(nullable UIEvent *)event;

截图7.png