画出背景图

好久没用了。

CGSize imageSize = CGSizeMake(50, 50);

UIGraphicsBeginImageContextWithOptions(imageSize, 0, [UIScreen mainScreen].scale);

[[UIColor colorWithRed:0/255.0 green:0/255.0 blue:0/255.0 alpha:1] set];

UIRectFill(CGRectMake(0, 0, imageSize.width, imageSize.height));

UIImage *pressedColorImg = UIGraphicsGetImageFromCurrentImageContext();

UIGraphicsEndImageContext();

[btn setBackgroundImage:pressedColorImg forState:UIControlStateHighlighted];

无需添加纯色图片文件，为button设置高亮背景，Do it like this . 妈妈再也不用担心了。