objective-c - 自定义 NSSliderCell

Question

我已经完成了一个自定义 slider 单元格的实现，该单元格可以使用滚动条和旋钮的图像进行绘制。现在唯一的障碍是，当我快速拖动旋钮时，图像会变得困惑。我已经发布了一个屏幕截图。

代码如下:

#import "customSliderCell.h"
@implementation customSliderCell
- (void)drawKnob:(NSRect)knobRect {

    NSImage * knob = knobImage;
 [[self controlView] lockFocus];
 [knob
 compositeToPoint:NSMakePoint(knobRect.origin.x,knobRect.origin.y+knobRect.size.height)
 operation:NSCompositeSourceOver];

[[self controlView] unlockFocus];
}
- (void)drawBarInside:(NSRect)rect flipped:(BOOL)flipped {
rect.size.height = 8;

    NSRect leftRect = rect;
    leftRect.origin.x=0;
    leftRect.origin.y=2;
    leftRect.size.width = knobrect.origin.x + (knobrect.size.width);
    [leftBarImage setSize:leftRect.size];
    [leftBarImage drawInRect:leftRect fromRect: NSZeroRect operation: NSCompositeSourceOver fraction:1];

    NSRect rightRect = rect;
    rightRect.origin.x=0;
    rightRect.origin.y=2;
    rightRect.origin.x = knobrect.origin.x;
    [rightBarImage setSize:rightRect.size];
    [rightBarImage drawInRect:rightRect fromRect: NSZeroRect operation: NSCompositeSourceOver fraction:1];
}

啊，我太接近了。任何关于为什么会发生这种情况以及如何解决它的帮助将不胜感激，谢谢!

Answer 1

好的，所以它想通了。显然， slider 试图变得聪明，只在旋钮所在的位置绘制。所以显然我必须通过覆盖 slider 类中的 setNeedsDisplayInRect 来始终使矩形无效。

#import "customSlider.h"

@implementation customSlider
-(void)setNeedsDisplayInRect:(NSRect)invalidRect{
    [super setNeedsDisplayInRect:[self bounds]];
}
@end