<pre>
- (void)drawRect:(CGRect)rect {
CGFloat y = 0;
CGContextRef context = UIGraphicsGetCurrentContext(); //高需要變
[self _drawGradientColor:context
rect:CGRectMake(0, y, self.frame.size.width, incrementHeight)
options:kCGGradientDrawsAfterEndLocation
colors:self.colorsArray];
CGContextStrokePath(context);// 描線,即繪制形狀
CGContextFillPath(context);// 填充形狀內(nèi)的顏色
}
/**
02
- 繪制背景色漸變的矩形血崭，p_colors漸變顏色設置腻扇，集合中存儲UIColor對象（創(chuàng)建Color時一定用三原色來創(chuàng)建）
03
**/
-
(void)_drawGradientColor:(CGContextRef)p_context
rect:(CGRect)p_clipRect options:(CGGradientDrawingOptions)p_options colors:(NSArray *)p_colors {CGContextSaveGState(p_context);// 保持住現(xiàn)在的context
CGContextClipToRect(p_context, p_clipRect);// 截取對應的context
NSUInteger colorCount = p_colors.count;
int numOfComponents = 4;
CGColorSpaceRef rgb = CGColorSpaceCreateDeviceRGB();
CGFloat colorComponents[colorCount * numOfComponents];
for (int i = 0; i < colorCount; i++) {
UIColor *color = p_colors[i]; CGColorRef temcolorRef = color.CGColor; const CGFloat *components = CGColorGetComponents(temcolorRef); for (int j = 0; j < numOfComponents; ++j) { colorComponents[i * numOfComponents + j] = components[j]; }}
CGGradientRef gradient = CGGradientCreateWithColorComponents(rgb, colorComponents, NULL, colorCount);
CGColorSpaceRelease(rgb);
CGPoint startPoint = p_clipRect.origin;
CGPoint endPoint = CGPointMake(CGRectGetMinX(p_clipRect), CGRectGetMaxY(p_clipRect));
CGContextDrawLinearGradient(p_context, gradient, startPoint, endPoint, p_options);
CGGradientRelease(gradient);
CGContextRestoreGState(p_context);// 恢復到之前的context
}
</pre>
