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两段代码，首先是使用方法
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CGContextRef context = UIGraphicsGetCurrentContext(); |
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NSArray *colors = [NSArray arrayWithObjects: |
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[UIColor colorWithRed:225.0 / 255.0 green:225.0 / 255.0 blue:225.0 / 255.0 alpha:1.0], |
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[UIColor colorWithRed:168.0 / 255.0 green:168.0 / 255.0 blue:168.0 / 255.0 alpha:1.0], |
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nil]; |
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[self _drawGradientColor:context |
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rect:CGRectMake(rX, rY, rW, rH) |
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options:kCGGradientDrawsAfterEndLocation |
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colors:colors]; |
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CGContextStrokePath(context);// 描线,即绘制形状 |
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CGContextFillPath(context);// 填充形状内的颜色 |
在一段就是绘制背景色渐变的矩形
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/** |
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* 绘制背景色渐变的矩形，p_colors渐变颜色设置，集合中存储UIColor对象（创建Color时一定用三原色来创建） |
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**/ |
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- (void)_drawGradientColor:(CGContextRef)p_context |
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rect:(CGRect)p_clipRect |
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options:(CGGradientDrawingOptions)p_options |
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colors:(NSArray *)p_colors { |
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CGContextSaveGState(p_context);// 保持住现在的context |
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CGContextClipToRect(p_context, p_clipRect);// 截取对应的context |
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int colorCount = p_colors.count; |
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int numOfComponents = 4; |
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CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB(); |
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CGFloat colorComponents[colorCount * numOfComponents]; |
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for (int i = 0; i < colorCount; i++) { |
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UIColor *color = p_colors[i]; |
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CGColorRef temcolorRef = color.CGColor; |
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const CGFloat *components = CGColorGetComponents(temcolorRef); |
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for (int j = 0; j < numOfComponents; ++j) { |
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colorComponents[i * numOfComponents + j] = components[j]; |
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} |
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} |
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CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colorComponents, NULL, colorCount); |
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CGColorSpaceRelease(rgb); |
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CGPoint startPoint = p_clipRect.origin; |
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CGPoint endPoint = CGPointMake(CGRectGetMinX(p_clipRect), CGRectGetMaxY(p_clipRect)); |
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CGContextDrawLinearGradient(p_context, gradient, startPoint, endPoint, p_options); |
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CGGradientRelease(gradient); |
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CGContextRestoreGState(p_context);// 恢复到之前的context |
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} |
还有一种实现方式
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CAGradientLayer *gradient = [CAGradientLayer layer]; |
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gradient.frame = CGRectMake(rX, rY, rW, rH); |
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gradient.colors = [NSArray arrayWithObjects: |
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(id)[UIColor blackColor].CGColor, |
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(id)[UIColor grayColor].CGColor, |
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(id)[UIColor blackColor].CGColor, |
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nil]; |
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[self.view.layer insertSublayer:gradient atIndex:0]; |
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原文地址：http://my.oschina.net/hejunbinlan/blog/469797
