NSScrollView 搞乱了 NSGradient （损坏）
我制作了一个自定义框，它是 NSBox 的子类。我重写 drawRect: 方法并在其中绘制渐变，如下所示（假设我已经有 start 和 end 颜色）：
-(void)drawRect:(NSRect)dirtyRect {
NSGradient *gradient = [[NSGradient alloc] initWithStartingColor:start endingColor:end];
[gradient drawInRect:dirtyRect angle:270];
[gradient release];
}
现在这个框被添加为 NSCollectionView 原型视图的子视图。在视图的原始状态下，它看起来像这样：
将视图滚动到视线之外并再次返回后，它看起来像这样：
为什么我的渐变会这样损坏，我该如何修复它？谢谢！
I have a custom box that I've made that is a subclass of NSBox. I override the drawRect: method and draw a gradient in it like this (assuming I already have a start & end color):
-(void)drawRect:(NSRect)dirtyRect {
NSGradient *gradient = [[NSGradient alloc] initWithStartingColor:start endingColor:end];
[gradient drawInRect:dirtyRect angle:270];
[gradient release];
}
Now this box is added as a subview of a prototype view for a NSCollectionView. In the view's original state it looks like this:
And after scrolling the view out of sight and back in again, it looks like this:
Why is my gradient getting corrupted like that, and how can I fix it? Thanks!
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该
dirtyRect参数不一定代表整个盒子。如果 Cocoa 决定只有原始帧的一个子帧需要（重新）绘制，则dirtyRect仅表示该子帧。如果您为整个帧绘制了渐变，然后（重新）为子帧绘制了相同的渐变，则它们可能不匹配。尝试：
相反。
进一步注意：看起来您的渐变对象可以被缓存，而不是在
-drawRect:内创建/释放。That
dirtyRectargument doesn’t necessarily represent the entire box. If Cocoa decides that only a subframe of the original frame needs (re)drawing,dirtyRectrepresents only that subframe. If you’ve drawn a gradient for the entire frame and then (re)draw the same gradient for a subframe, it's likely they won't match.Try:
instead.
One further note: it looks like your gradient object could be cached instead of being created/released inside
-drawRect:.您的问题是您正在
dirtyFrame中绘制，而不是框的整个矩形。我不知道这是否正确，但试试这个：Your problem is you're drawing in
dirtyFrame, not the entire rectangle of the box. I have no idea if this is correct, but try this: