說到iOS中的觸摸事件不得不提到兩個內(nèi)容：一個是UIResponder起愈、一個是事件的響應(yīng)鏈

什么UIResponser敞峭？

Responsder objects是UIResponder的實例化對象铛铁，他組成了事件處理的骨架赶撰，許多關(guān)鍵對象都是UIResponder對象包括UIApplication月帝、UIViewController阱扬、UIView也包括UIWindow。
也就是說只要繼承UIResponder的類都可以相應(yīng)事件捻撑。

一般我們通過重寫UIResponder的四個方法來處理事件

// 一根或者多根手指開始觸摸view
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
// 一根或者多根手指在view上移動磨隘，【會多次調(diào)用】
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
// 一根或者多根手指離開view
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
// 觸摸結(jié)束前，某個系統(tǒng)事件(例如電話呼入)會打斷觸摸過程
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
// 提示：touches中存放的都是UITouch對象

響應(yīng)鏈

一個觸摸事件是從用戶點擊屏幕開始 由UIApplication向下分發(fā) 經(jīng)由 UIWindow 在向下傳遞給UIViewController和UIVIew
那么 我們一個UIViewController有那么多View到底事件應(yīng)該交給誰消費掉呢顾患？
有兩個重要的方法

• hitTest:withEvent:
• pointInside:withEvent:

他們的作用分別是
hitTest:withEvent:尋找并返回最合適的view番捂、
pointInside:withEvent: 判斷點是否在當(dāng)前的View上

• 兩個方法調(diào)用順序
  我們通過實例驗證一下 新建四個View并重寫他們的touchesXXX方法、hitTest:withEvent: 方法江解、以及pointInside:withEvent:方法并打印方法名和類名

  
  
  views

//示例 其他View以此為模板
#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中添加他們
//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];

運行后的效果圖

運行圖

當(dāng)我們點擊灰色View時设预，控制臺打印如下信息

console

有幾點回影響hitTest流程當(dāng)

• alpha<=0.01
• userInterActionEnabled = NO
• hidden = YES;
  pointInside都會返回NO

我們可以根據(jù)上面的結(jié)論自己寫一下hitTest的內(nèi)部邏輯驗證推論是否正確

//GrayView.m
- (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
{
   
    NSLog(@"%s",__func__);
    //逆序遍歷子VIew看觸摸點是否在子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]) {
        //點不在子View中而在自己身上
        return self;
    } else {
        //觸摸點不在當(dāng)前View上
        return nil;
        
    }
    

}

我們依然點擊GrayView發(fā)現(xiàn)依然可以找到正確被點擊的View

console

現(xiàn)在我們給RedView的hitTest方法打一個斷點看并點擊RedView查看調(diào)用層級

responder_chain