objective-c - iOS 在部分 View 中绘制渐变

Question

我创建了一个自定义进度条，它继承了 UIView 并实现了 drawRect。我设法在整个 View 上绘制了一个渐变。但是，我想绘制几个不同的渐变，每个渐变都在不同的位置。如何限制 CGContextDrawLinearGradient在我的视野中缩小矩形？

glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);
CGPoint topCenter = CGPointMake(start + (CGRectGetMidX(currentBounds)/currentBounds.size.width), 0.0f);`
        CGPoint midCenter = CGPointMake(start + (CGRectGetMidX(currentBounds)/currentBounds.size.width), currentBounds.size.height);
        CGContextDrawLinearGradient(currentContext, glossGradient, topCenter, midCenter, 0);
        start = start + (values[i] / currentBounds.size.width);
        CGGradientRelease(glossGradient);
    }

Answer 1

您可以使用 CGContectClipToRect限制绘图区域

然后对每个梯度做:

CGContextSaveGState(currentContext);
CGContextClipToRect(theRect); // theRect should be the area where you want to draw the gradient
... // gradient drawing code
CGContextRestoreGState(currentContext);