突出显示时更改 UIButton 的背景颜色 [英] Change background color of UIButton when Highlighted

问题描述

您好，我想更改用户点击按钮的 UIButton 背景颜色.

Hi I want to change the UIButton background color which user Tap on the button.

我正在使用渐变显示背景颜色，当用户点击时我需要更改渐变颜色.

I am showing background color using gradient, when user tap I need to change the gradient color.

[btn setTitle: @"Next" forState:UIControlStateNormal];
CAGradientLayer *gradient = [CAGradientLayer layer];            
gradient.frame = btn.bounds;
gradient.cornerRadius = 10.0f;
locations = [[NSArray alloc] initWithObjects: 0.0f, 0.0f, 0.0f,0.0f, nil]; 
[gradient setLocations:locations];
colorNext = [[NSArray alloc] initWithObjects:…., nil]; 
gradient.colors = colorNext;
[locations release];
[btn.layer insertSublayer:gradient atIndex:0];
btn.titleLabel.textColor = [UIColor blackColor];

推荐答案

不建议更改 UIButton 的内部层级，因为它可能会在未来的 iOS 更新中中断.此外，它可能会导致 Apple 拒绝您的申请.更好的解决方案是创建一个按钮子类.这是一个如何做的例子:

Changing the internal layer hierarchy of a UIButton is not recommended since it may break in a future update of the iOS. Also, it may cause Apple to reject your application. A better solution would be to create a button subclass. Here is an example of how to do it:

@interface MyButton : UIButton
@end

@implementation MyButton

- (id)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame])
    {
        [self addObserver:self forKeyPath:@"highlighted" options:NSKeyValueObservingOptionNew context:NULL];
    }

    return self;
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
    [self setNeedsDisplay];
}

- (void)drawRect:(CGRect)rect
{
    [super drawRect:rect];

    if (self.highlighted == YES)
    {
        CGContextRef ctx = UIGraphicsGetCurrentContext();

        CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();

        const CGFloat *topGradientColorComponents = CGColorGetComponents([UIColor whiteColor].CGColor);
        const CGFloat *bottomGradientColorComponents = CGColorGetComponents([UIColor blackColor].CGColor);

        CGFloat colors[] =
        {
            topGradientColorComponents[0], topGradientColorComponents[1], topGradientColorComponents[2], topGradientColorComponents[3],
            bottomGradientColorComponents[0], bottomGradientColorComponents[1], bottomGradientColorComponents[2], bottomGradientColorComponents[3]
        };
        CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colors, NULL, sizeof(colors) / (sizeof(colors[0]) * 4));
        CGColorSpaceRelease(rgb);

        CGContextDrawLinearGradient(ctx, gradient, CGPointMake(0, 0), CGPointMake(0, self.bounds.size.height), 0);
        CGGradientRelease(gradient);
    }
    else
    {
        // Do custom drawing for normal state
    }
}

- (void)dealloc
{
    [self removeObserver:self forKeyPath:@"highlighted"];

    [super dealloc];
}

@end

您可能需要对其进行一些修改以使其执行您想要的操作，但我认为您已了解基本概念.

You may need to modify it a bit to get it to do what you want but I think you get the basic idea.

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