说到iOS中的触摸事件不得不提到两个内容：一个是UIResponder、一个是事件的响应链
什么UIResponser？
Responsder objects是UIResponder的实例化对象，他组成了事件处理的骨架，许多关键对象都是UIResponder对象包括UIApplication、UIViewController、UIView也包括UIWindow。
也就是说只要继承UIResponder的类都可以相应事件。
一般我们通过重写UIResponder的四个方法来处理事件
// 一根或者多根手指开始触摸view
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
// 一根或者多根手指在view上移动，【会多次调用】
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
// 一根或者多根手指离开view
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
// 触摸结束前，某个系统事件(例如电话呼入)会打断触摸过程
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
// 提示：touches中存放的都是UITouch对象
响应链
一个触摸事件是从用户点击屏幕开始 由UIApplication向下分发 经由 UIWindow 在向下传递给UIViewController和UIVIew
那么 我们一个UIViewController有那么多View到底事件应该交给谁消费掉呢？
有两个重要的方法
- hitTest:withEvent:
- pointInside:withEvent:
他们的作用分别是
hitTest:withEvent:寻找并返回最合适的view、
pointInside:withEvent: 判断点是否在当前的View上
-
两个方法调用顺序
我们通过实例验证一下 新建四个View并重写他们的touchesXXX方法、hitTest:withEvent: 方法、以及pointInside:withEvent:方法并打印方法名和类名
views
//示例 其他View以此为模板
#import "GrayView.h"
@implementation GrayView
- (void)layoutSubviews
{
self.backgroundColor = [UIColor grayColor];
}
- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event
{
NSLog(@"%@ pointInside", NSStringFromClass([self class]));
return [super pointInside:point withEvent:event];
}
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
NSLog(@"%@ hitTest", NSStringFromClass([self class]));
return [super hitTest:point withEvent:event];
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
NSLog(@"%@ touchBegan", NSStringFromClass([self class]));
[super touchesBegan:touches withEvent:event];
}
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
NSLog(@"%@ touchesMoved",NSStringFromClass([self class]));
[super touchesMoved:touches withEvent:event];
}
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
NSLog(@"%@ touchesEnded", NSStringFromClass([self class]));
[super touchesEnded:touches withEvent:event];
}
- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
NSLog(@"%@ touchesCancelled", NSStringFromClass([self class]));
[super touchesCancelled:touches withEvent:event];
}
@end
//在ViewController中添加他们
//ViewController.m
GrayView *grayView = [[GrayView alloc] initWithFrame:CGRectMake(50.f, 100.f, 260.f, 200.f)];
RedView *redView = [[RedView alloc] initWithFrame:CGRectMake(0.f, 0.f, 120.f, 100.f)];
BlueView *blueView = [[BlueView alloc] initWithFrame:CGRectMake(140.f, 100.f, 100.f, 100.f)];
YellowView *yellowView = [[YellowView alloc] initWithFrame:CGRectMake(50.f, 360.f, 200.f, 200.f)];
[self.view addSubview:grayView];
[grayView addSubview:redView];
[grayView addSubview:blueView];
[self.view addSubview:yellowView];
运行后的效果图
运行图
当我们点击灰色View时，控制台打印如下信息
console
我们看到最先调用了YellowView的hitTest方法而后调用pointInside方法，如果pointInside返回NO说明这个触摸点不在这个View上就遍历跟他同一级的下一个View，如果pointInside返回YES说明触摸点在这个View的范围内，则逆序遍历他的子View，如果子View的pointInside都返回NO那么说明这个触摸点在当前返回YES的这个View上
有几点回影响hitTest流程当
- alpha<=0.01
- userInterActionEnabled = NO
- hidden = YES;
pointInside都会返回NO
我们可以根据上面的结论自己写一下hitTest的内部逻辑验证推论是否正确
//GrayView.m
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
NSLog(@"%s",__func__);
//逆序遍历子VIew看触摸点是否在子View中
NSArray *subViews = [[self.subviews reverseObjectEnumerator] allObjects];
UIView *tmpView = nil;
for (UIView *view in subViews) {
CGPoint convertedPoint = [self convertPoint:point toView:view];
if ([view pointInside:convertedPoint withEvent:event]) {
tmpView = view;
break;
}
}
if (tmpView) {
//在子View中
return tmpView;
} else if([self pointInside:point withEvent:event]) {
//点不在子View中而在自己身上
return self;
} else {
//触摸点不在当前View上
return nil;
}
}
我们依然点击GrayView发现依然可以找到正确被点击的View
console
现在我们给RedView的hitTest方法打一个断点看并点击RedView查看调用层级
responder_chain
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