ios点击改变uiview背景颜色

ios点击改变uiview背景颜色是一个再常见不过的需求。第一反应应该不麻烦，于是写了个第一个版本

@interface RespondentUIView()
{
    UIColor * bgColor;
}
@end

@implementation RespondentUIView
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
 {
    bgColor = self.backgroundColor;
    self.backgroundColor = White_Down;
 }

 - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
    self.backgroundColor = bgColor;
 }

@end

好像也能用。但是一会问题来了。发现touchesBegan很延时很严重的样子。于是有了第二个版本。

@interface RespondentUIView()
{
    UIColor * bgColor;
}
@end

@implementation RespondentUIView

- (void)willMoveToSuperview:(UIView *)newSuperview
{
    UILongPressGestureRecognizer *tapRecognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(changeColor:)];
    tapRecognizer.minimumPressDuration = 0;//Up to you;
    tapRecognizer.cancelsTouchesInView = NO;
    [self addGestureRecognizer:tapRecognizer];
}

-(void) changeColor:(UIGestureRecognizer *)gestureRecognizer{
    
    if (gestureRecognizer.state == UIGestureRecognizerStateBegan)
    {
        bgColor = self.backgroundColor;
        self.backgroundColor = White_Down;
    }
    else if (gestureRecognizer.state == UIGestureRecognizerStateEnded)
    {
        self.backgroundColor = bgColor;
    }
}
@end

用UILongPressGestureRecognizer一下子就好多了，点击反应嗖嗖的。一会又发现问题了，有的view需要注册点击事件，一个uiView注册多个UIGestureRecognizer时，总有一个不响应。真是shit。于是又google一通，发现了一个uiview使用多个

UIGestureRecognizer的方法，于是有了第三版。

@interface RespondentUIView()<UIGestureRecognizerDelegate>
{
    UIColor * bgColor;
}
@end

@implementation RespondentUIView

- (void)willMoveToSuperview:(UIView *)newSuperview
{
    UILongPressGestureRecognizer *tapRecognizer = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(changeColor:)];
    tapRecognizer.minimumPressDuration = 0;//Up to you;
    tapRecognizer.cancelsTouchesInView = NO;
    tapRecognizer.delegate = self;
    [self addGestureRecognizer:tapRecognizer];
}

-(void) changeColor:(UIGestureRecognizer *)gestureRecognizer{
    
    if (gestureRecognizer.state == UIGestureRecognizerStateBegan)
    {
        bgColor = self.backgroundColor;
        self.backgroundColor = White_Down;
    }
    else if (gestureRecognizer.state == UIGestureRecognizerStateEnded)
    {
        self.backgroundColor = bgColor;
    }
}


//下面三个函数用于多个GestureRecognizer 协同作业，避免按下的手势影响了而别的手势不响应
- (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer
{
    return YES;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer
{
    return YES;
}

- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldReceiveTouch:(UITouch *)touch
{
    return YES;
}
@end

这下感觉整个世界清静了。顺带提一下

tapRecognizer.cancelsTouchesInView = NO;
这是一个很犀利的属性。一般ios响应链传递的顺序是先交给UIView的UIGestureRecognizer处理。如果它处理了，就把事件丢掉了，于是UIView上面的touchesBegan和touchesEnded等优先级比较低的UIResponder就没机会响应了。把cancelsTouchesInView置为NO。于是大家就能和谐相处了。