ios點擊改變uiview背景顏色

ios點擊改變uiview背景顏色是一個再常見不過的需求。第一反應應該不麻煩，於是寫了個第一個版本

@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。但是一會問題來了。發現touchesBegan很延時很嚴重的樣子。於是有了第二個版本。

@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，點擊反應嗖嗖的。一會又發現問題了，有的view需要注冊點擊事件，一個uiView注冊多個UIGestureRecognizer時，總有一個不響應。真是shit。於是又google一通，發現了一個uiview使用多個

UIGestureRecognizer的方法，於是有了第三版。

@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;
    }
}


//下面三個函數用於多個GestureRecognizer 協同作業，避免按下的手勢影響了而別的手勢不響應
- (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

這下感覺整個世界清靜了。順帶提一下

tapRecognizer.cancelsTouchesInView = NO;
這是一個很犀利的屬性。一般ios響應鏈傳遞的順序是先交給UIView的UIGestureRecognizer處理。如果它處理了，就把事件丟掉了，於是UIView上面的touchesBegan和touchesEnded等優先級比較低的UIResponder就沒機會響應了。把cancelsTouchesInView置為NO。於是大家就能和諧相處了。