事件运用案例

一、视图遮挡按钮，按钮无法响应点击事件。

如图一所示，红色按钮在蓝色视图的下面，如何来点击蓝色视图，让红色按钮也能响应他的点击事件呢？

图一.png

重写蓝色视图的pointInside方法,使其返回NO.其原理在事件响应原理已经做出了解释。

- (BOOL)pointInside:(CGPoint)point withEvent:(UIEvent *)event{
    NSLog(@"%s",__func__);
    return NO;
    //return [super pointInside:point withEvent:event];
}

二、将按钮添加到scollView上，当按钮出现高亮显示的时候无法滑动scrollView，当滑动scrollView的时候无法显示按钮的高亮状态。

图二.png

1、delaysContentTouches

默认状态下这个属性为YES，当设置为NO的情况下，手指触摸scrollView上的按钮区域，按钮的高亮状态会立马显示，但是scrollView的滑动事件被取消。

2、canCancelContentTouches

默认状态下这个属性为YES，它会自动调用- (BOOL)touchesShouldCancelInContentView:(UIView *)view；这个方法。如果为NO，则不会调用这个方法。如果touchesShouldCancelInContentView返回为NO，scrollView不会传递touch事件给subViews。
要想scrollView上的按钮同时响应scrollView的滑动事件和按钮的高亮事件，必须做如下设置：

//设置为NO，当手指在按钮上的时候，滑动scrollView时，会立马响应按钮的高亮状态，
//如果该属性设置为YES，那么要等手指放在按钮上停留一会按钮才会响应高亮状态。
scrollView.delaysContentTouches = NO;
scrollView.canCancelContentTouches = YES;

重写scrollView方法

- (BOOL)touchesShouldCancelInContentView:(UIView *)view{
    [super touchesShouldCancelInContentView: view];
    return YES;
}

三、如果将scrollView下面的子视图也能响应touch事件，那么必须重写scrollView的touch方法。如下所示:

- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    NSLog(@"%s",__func__);
    [self.nextResponder touchesBegan:touches withEvent:event];
}
- (void)touchesMoved:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    NSLog(@"%s",__func__);
    [self.nextResponder touchesMoved:touches withEvent:event];
}
- (void)touchesCancelled:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    NSLog(@"%s",__func__);
    [self.nextResponder touchesCancelled:touches withEvent:event];
}
- (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
    NSLog(@"%s",__func__);
    [self.nextResponder touchesEnded:touches withEvent:event];
}

四、UIScollView上的触摸案例

2017-04-03 21_57_26.gif

代码如下：

- (void)viewDidLoad {
    [super viewDidLoad];
    self.view.backgroundColor = [UIColor redColor];
    UIScrollView * scrollView = [[UIScrollView alloc] initWithFrame:CGRectMake(20, 100, WIN_WIDTH - 60, (WIN_WIDTH - 60) / 2)];
    scrollView.backgroundColor = [UIColor whiteColor];
    scrollView.pagingEnabled = YES;
    scrollView.clipsToBounds = NO;
    scrollView.contentSize = CGSizeMake(5 * (WIN_WIDTH - 60), (WIN_WIDTH - 60) / 2);
    [self.view addSubview:scrollView];
    NSArray * imageArr = @[@"0",@"1",@"2",@"3",@"4"];
    for (NSInteger i = 0; i < 5; i++) {
        UIImageView * imgView = [[UIImageView alloc] initWithFrame:CGRectMake(i * (WIN_WIDTH - 60) + 20,0, WIN_WIDTH - 80, (WIN_WIDTH - 60) / 2)];
        imgView.image = [UIImage imageNamed:imageArr[i]];
        [scrollView addSubview:imgView];
    }
}

五、UIScreenEdgePanGestureRecognizer

- (void)createScreenGestureView {
    
    UIScreenEdgePanGestureRecognizer *screenEdgePanGesture = [[UIScreenEdgePanGestureRecognizer alloc] initWithTarget:self action:@selector(panAction:)];
    NSArray *gestureArray = self.navigationController.view.gestureRecognizers;
    for (UIGestureRecognizer *gesture in gestureArray) {
        if ([gesture isKindOfClass:[UIScreenEdgePanGestureRecognizer class]]) {
            [gesture requireGestureRecognizerToFail:screenEdgePanGesture];
        }
    }
    screenEdgePanGesture.edges = UIRectEdgeRight;
    [self.showView addGestureRecognizer:screenEdgePanGesture];
}
#pragma mark - event response
- (void)panAction:(UIScreenEdgePanGestureRecognizer *)gesture
{
    //找到手势作用的视图
    UIView *view = [self.view hitTest:[gesture locationInView:gesture.view] withEvent:nil];
    NSLog(@"view.tag %ld, gesture.view %ld", view.tag, gesture.view.tag);
    if (UIGestureRecognizerStateBegan == gesture.state || UIGestureRecognizerStateChanged == gesture.state) {
        CGPoint translationPoint = [gesture translationInView:gesture.view];
        _backgroundView.center = CGPointMake(center_x+translationPoint.x, center_y);
    } else {
        [UIView animateWithDuration:.3f animations:^{
            _backgroundView.center = CGPointMake(center_x, center_y);
        }];
    }
}

六、scrollView上添加UISlider,如果scrollView的contentSize比frame要大，那么滑动UISlider会滑动scrollView。设置delaysContentTouches属性为NO。