macOSNSView改变frame后会出现黑色残留，应付的办法是不在drawRect上修改重新initWithFrame一下就行

黑色部分就是残留。是因为绘制后保留了轨迹。

解决办法是不在drawRect中做处理重新写NSView，新增方法 initWithFrame

- (void)drawRect:(NSRect)dirtyRect {
[super drawRect:dirtyRect];
//cocoa方法的改变背景颜色
[[NSColor redColor] setFill];
NSRectFill(dirtyRect);
// Drawing code here.
// CGFloat lineWidth = 2.0;
// // Drawing code here.
// NSBezierPath* bgPath = [NSBezierPath bezierPathWithRoundedRect:NSInsetRect(dirtyRect, 10.0f, 10.0f) xRadius:3.0 yRadius:3.0];
// [bgPath setLineWidth:lineWidth];
// [bgPath setClip];
// [[NSColor purpleColor] setFill];
// [bgPath fill];
}
- (instancetype)initWithFrame:(NSRect)frame
{
self = [super initWithFrame:frame];
if (self) {
[self setWantsLayer:YES];
self.layer.backgroundColor = CGColorCreateGenericRGB(1.0, 0, 0, 1.0);
// NSShadow *shadow = [[NSShadow alloc] init];
// [shadow setShadowColor: [NSColor redColor]];
// [shadow setShadowBlurRadius:4.0];
// [self setShadow:shadow];
// [self addSubview:self.klineVC.view];
// [self.klineVC.view mas_makeConstraints:^(MASConstraintMaker *make) {
// (void)make.edges;
// }];
}
return self;
}

效果如图所示