我有一个带有透明背景和白色标题的自定义UIButton
。
我正在寻找一个简单的解决方案,在高亮(白色背景和透明标题)上将其反转,因为它在系统UISegmentedControl
上实现。
是否比在用作CALayer
掩码的快照上反转alpha更简单?
如果没有,你能告诉我如何反转CALayer
alpha?
答案 0 :(得分:5)
您可以使用Destination Out作为混合模式在CGContext上绘制文本。
此代码似乎有效:
- (void)viewDidLoad
{
[super viewDidLoad];
self.view.backgroundColor = [UIColor greenColor];
UIFont* font = [UIFont fontWithName:@"Helvetica-Bold" size:18];
NSString* buttonText = @"BUTTON";
CGSize buttonSize = CGSizeMake(200, 50);
NSDictionary* textAttributes = @{NSFontAttributeName:font};
CGSize textSize = [buttonText sizeWithAttributes:textAttributes];
UIGraphicsBeginImageContextWithOptions(buttonSize, NO, [[UIScreen mainScreen] scale]);
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(ctx, [UIColor redColor].CGColor);
UIBezierPath *path = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, buttonSize.width, buttonSize.height)];
CGContextAddPath(ctx, path.CGPath);
CGContextFillPath(ctx);
CGContextSetBlendMode(ctx, kCGBlendModeDestinationOut);
CGPoint center = CGPointMake(buttonSize.width/2-textSize.width/2, buttonSize.height/2-textSize.height/2);
[@"BUTTON" drawAtPoint:center withAttributes:textAttributes];
UIImage* viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView* imgView = [[UIImageView alloc] initWithImage:viewImage];
[self.view addSubview:imgView];
}
顺便说一句,如果你想在UIButton中设置UIImage而不是只是将它添加到视图中:
UIButton* boton = [[UIButton alloc] initWithFrame:CGRectMake(50, 50, viewImage.size.width, viewImage.size.height)];
[boton setBackgroundColor:[UIColor clearColor]];
[boton setTitleColor:[UIColor redColor] forState:UIControlStateNormal];
boton.titleLabel.font = font;
[boton setTitle:buttonText forState:UIControlStateNormal];
[boton setImage:viewImage forState:UIControlStateHighlighted];
[self.view addSubview:boton];
答案 1 :(得分:0)
你可以设置
-(void)viewDidload: {
[yourButton setTitleColor:(UIColor *)color
forState:UIControlStateHighlighted];
[yourButton addTarget:self
action:@selector(changeButtonBackGroundColor:)
forControlEvents:UIControlEventTouchDown];
}
-(void)changeButtonBackGroundColor:(UIButton *)button {
[button setBackgroundColor:[UIColor yourColor]];
}
请记住使用以下事件进行更改:UIControlEventTouchUpInside
和UIControlEventTouchOutSide
:)