iOS事件传递底层实现

1、iOS事件传递主要依靠下面两个方法实现：

• (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event

• (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event

2、-hitText方法的底层实现：

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
    // 1.判断能否接收触摸事件
    if (self.userInteractionEnabled == NO || self.hidden == YES || self.alpha <= 0.01) return nil;

    // 2.判断点在不在视图上
    if (![self pointInside:point withEvent:event]) return nil;

    // 3.遍历子控件
    int count = (int)self.subviews.count;
    for (int i = count - 1; i >= 0; i--) {
        UIView *childView = self.subviews[i];
    
        CGPoint childViewP = [self convertPoint:point toView:childView];
    
        UIView *fitView = [childView hitTest:childViewP withEvent:event];
        if (fitView) {
            return fitView;
        }
    }  
     // 如果都没有找到返回本身
     return self;
}

3、利用-hitTest方法来实现点击穿透效果

- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
    UIView *hitView = [super hitTest:point withEvent:event];
    if (self.canTouch) {
        return hitView;
    }
    if (hitView == self)
    {
        return nil;
    }
    else
    {
        return hitView;
    }
}

只要canTouch属性为NO，点击实现该方法的view时，将穿透该view而到达其下面的view，从而触发下层view的触摸事件。

4、pointInside方法实现穿透效果

23D3D8F9-328B-4E4E-AD3C-77B6C5B208C2.png

图中橙色按钮位于浅绿色view的下面，当点击橙色区域时，点击事件将穿透浅绿色view而响应橙色按钮。

下面给出实现代码：
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
CGPoint btnP = [self convertPoint:point toView:_btn];
BOOL flag = [_btn pointInside:btnP withEvent:event];
if (flag) {
return NO;
}
return [super pointInside:point withEvent:event];

}