6

我并没有真正用 Core Graphics 做过很多编程。而且我现在倾向于坚持使用 QuartzCore，因为它通过 layer 属性做了很多我需要的事情:)

但是，我有一个 UIView，它目前是渐变的。我想为这个 UIView 添加圆角，当我绘制渐变时，图层属性不会这样做：

- (void)drawRect:(CGRect)rect {
    CGContextRef currentContext = UIGraphicsGetCurrentContext();

    CGGradientRef glossGradient;
    CGColorSpaceRef rgbColorspace;
    size_t num_locations = 2;
    CGFloat locations[2] = { 0.0, 1.0 };
    CGFloat components[8] = { 1.0, 1.0, 1.0, 0.95,  // Start color
                            1.0, 1.0, 1.0, 0.60 }; // End color

    rgbColorspace = CGColorSpaceCreateDeviceRGB();
    glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);

    CGRect currentBounds = self.bounds;
    CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
    CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMaxY(currentBounds));
    CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);

    CGGradientRelease(glossGradient);
    CGColorSpaceRelease(rgbColorspace);
}

我不确定在 drawRect 方法中应该在哪里舍入。谢谢。

4

2 回答 2

7

你检查过以前的问题帖子吗？不久前我读过一篇关于屏蔽 UIViews 的文章。我认为这几乎适用于所有使用 drawRect 的对象

如何在 iPhone SDK 中将方形图像屏蔽为圆角图像？

这就是我所做的，据我所知，它工作得很好。

首先，我从上面提到的帖子中借用了NilObject先生的代码片段。

我对其进行了修改以适合对象（因为他将其编写为 C 函数而不是方法）

我继承 UIView 来创建我自己的自定义视图。我重载 initWithRect: 以使我的背景透明。

所以基本上：

  • 设置透明背景（在 init 中），否则剪辑会很丑
  • 在drawRect中，先剪辑，然后在剪辑区域内绘制

以下是一个工作示例：

//
//  TeleView.m
//

#import "TeleView.h"


@implementation TeleView
/**** in init methods, set background to transparent,
      otherwise, clipping shows a black background ****/

- (id) initWithFrame:(CGRect)frame {
    if((self = [super initWithFrame:frame])) {
        [self setBackgroundColor:[UIColor colorWithWhite:0.0f alpha:0.0f]];
    }
    return self;
}
- (void) clipCornersToOvalWidth:(float)ovalWidth height:(float)ovalHeight
{
    float fw, fh;
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect rect = CGRectMake(0.0f, 0.0f, self.frame.size.width, self.frame.size.height);

    if (ovalWidth == 0 || ovalHeight == 0) {
        CGContextAddRect(context, rect);
        return;
    }
    CGContextSaveGState(context);
    CGContextTranslateCTM (context, CGRectGetMinX(rect), CGRectGetMinY(rect));
    CGContextScaleCTM (context, ovalWidth, ovalHeight);
    fw = CGRectGetWidth (rect) / ovalWidth;
    fh = CGRectGetHeight (rect) / ovalHeight;
    CGContextMoveToPoint(context, fw, fh/2);
    CGContextAddArcToPoint(context, fw, fh, fw/2, fh, 1);
    CGContextAddArcToPoint(context, 0, fh, 0, fh/2, 1);
    CGContextAddArcToPoint(context, 0, 0, fw/2, 0, 1);
    CGContextAddArcToPoint(context, fw, 0, fw, fh/2, 1);
    CGContextClosePath(context);
    CGContextRestoreGState(context);
}

-(void)drawRect:(CGRect)rect {
    CGContextRef currentContext = UIGraphicsGetCurrentContext();
    /**** here is what I modified. ****/
    [self clipCornersToOvalWidth:20.0f height:20.0f];
    CGContextClip(currentContext);

    /**** below this is your own code ****/
    CGGradientRef glossGradient;
    CGColorSpaceRef rgbColorspace;
    size_t num_locations = 2;
    CGFloat locations[2] = { 0.0, 1.0 };
    CGFloat components[8] = { 1.0, 0.0, 0.0, 0.60,  // Start color
    0.0, 1.0, 0.0, 0.40 }; // End color

    rgbColorspace = CGColorSpaceCreateDeviceRGB();
    glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);

    CGRect currentBounds = self.bounds;
    CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
    CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMaxY(currentBounds));
    CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);

    CGGradientRelease(glossGradient);
    CGColorSpaceRelease(rgbColorspace); 

}

@end
于 2009-12-14T21:09:11.757 回答
7 
NSArray *colors = [NSArray arrayWithObjects:fromColor.CGColor,toColor.CGColor, nil];

NSNumber *stopOne = [NSNumber numberWithFloat:0.0];
NSNumber *stopTwo = [NSNumber numberWithFloat:1.0];

NSArray *locations = [NSArray arrayWithObjects:stopOne, stopTwo, nil];

CAGradientLayer *headerLayer = [CAGradientLayer layer];
headerLayer.colors = colors;
headerLayer.locations = locations;

headerLayer.borderColor = borderColor.CGColor; // border line color**strong text**
headerLayer.borderWidth = width;// For Thickness of border line
headerLayer.cornerRadius = radius;//For Rounded Corner if You want to make rounded Corner

headerLayer.frame = frame;

[view.layer  insertSublayer:headerLayer atIndex:0];

还要确保导入“QuartzCore”框架

于 2013-06-14T14:35:13.877 回答