两种方法给View添加渐变颜色
一.CAGradientLayer添加渐变颜色
该方法我是写在了UIView的一个分类当中，所以self就是指的view，
Direction为自定义枚举，用来判断是横向渐变还是竖向渐变。
任何继承UIView的子类都可以直接调用。
/*
*colors：渐变颜色数组
*locations：变化位置 0 -- 1，和颜色数组元素个数对应
*direction：方向 横 竖
*/
- (void)setCAGradientLayerGradualColorWithColors:(NSArray<UIColor *> *)colors locations:(NSArray<NSNumber *> *)locations direction:(Direction)direction{
CAGradientLayer * gradientLayer = [CAGradientLayer layer];
NSMutableArray * colorsM = @[].mutableCopy;
for (int i = 0; i < colors.count; i ++) {
UIColor * color = colors[i];
[colorsM addObject:(__bridge id)color.CGColor];
}
gradientLayer.colors = colorsM;
gradientLayer.locations = locations;
gradientLayer.startPoint = CGPointMake(0, 0);
gradientLayer.endPoint = CGPointMake(0, 1.0);
if (direction == DirectionHorizontal) {
gradientLayer.endPoint = CGPointMake(1.0, 0);
}
gradientLayer.frame = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
[self.layer addSublayer:gradientLayer];
}
二. Core Graphics相关方法添加渐变颜色
/*
*colors：渐变颜色数组
*locations：变化位置 0 -- 1，和颜色数组元素个数对应
*direction：方向 横 竖
*/
- (void)setGraphicsColorWithColors:(NSArray<UIColor *>*)colors locations:(NSArray<NSNumber *> *)locations direction:(Direction)direction{
//创建CGContextRef
UIGraphicsBeginImageContext(self.bounds.size);
CGContextRef gc = UIGraphicsGetCurrentContext();
//创建CGMutablePathRef
CGMutablePathRef path = CGPathCreateMutable();
//绘制path
CGRect rect = CGRectMake(0, 0, self.frame.size.width, self.frame.size.height);
CGPathMoveToPoint(path, NULL, CGRectGetMinX(rect), CGRectGetMinY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMaxX(rect), CGRectGetMinY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMaxX(rect), CGRectGetMaxY(rect));
CGPathAddLineToPoint(path, NULL, CGRectGetMinX(rect), CGRectGetMaxY(rect));
CGPathCloseSubpath(path);
//绘制渐变
[self drawLinearGradient:gc path:path colors:colors locations:locations direction:direction];
//注意释放CGMutablePathRef
CGPathRelease(path);
//从Context中获取图像，并显示在界面上
UIImage * img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
UIImageView * imageView = [[UIImageView alloc] initWithImage:img];
[self addSubview:imageView];
}
//线性
- (void)drawLinearGradient:(CGContextRef)context path:(CGPathRef)path colors:(NSArray<UIColor *> *)colors locations:(NSArray<NSNumber *> *)locations direction:(Direction)direction{
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGFloat floatLocations[locations.count];
for (int i = 0; i < locations.count; i ++) {
floatLocations[i] = [locations[i] floatValue];
}
NSMutableArray * colorsM = @[].mutableCopy;
for (int i = 0; i < colors.count; i ++) {
UIColor * color = colors[i];
[colorsM addObject:(__bridge id)color.CGColor];
}
CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)colorsM, floatLocations);
CGRect pathRect = CGPathGetBoundingBox(path);
//具体方向可根据需求修改
CGPoint startPoint = CGPointMake(CGRectGetMinX(pathRect), CGRectGetMidY(pathRect));
CGPoint endPoint = CGPointMake(CGRectGetMaxX(pathRect), CGRectGetMidY(pathRect));
if (direction == DirectionVertical) {
startPoint = CGPointMake(CGRectGetMinX(pathRect), CGRectGetMinY(pathRect));
endPoint = CGPointMake(CGRectGetMinX(pathRect), CGRectGetMaxY(pathRect));
}
CGContextSaveGState(context);
CGContextAddPath(context, path);
CGContextClip(context);
CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, 0);
CGContextRestoreGState(context);
CGGradientRelease(gradient);
CGColorSpaceRelease(colorSpace);
}
Demo中还有一个圆形半径方向的渐变效果可以下载下来进行查看。