在 NSView-drawRect: 方法中画线的首选/推荐方法是什么？

Question

我在 NSView 级别的 Cocoa 中找不到任何线条绘制原语。我唯一找到的是NSBezierPath。这是首选方式吗？还是有其他我没发现的方法？

Answer 1

NSBezierPath 正是您应该使用的。如果你只是想从一个点到另一个点画一条直线，使用类方法：

+strokeLineFromPoint:(NSPoint)point1 toPoint:(NSPoint)point2

Answer 2

Cocoa 使用隐式绘图堆栈和失效模型。在您的 NSView 中，当状态更改会导致视图以不同方式绘制时，您调用 -[self setNeedsDisplay:] 来告诉绘图系统您需要重绘。在不久的将来，实际上是当前事件循环结束时，您的视图的 drawRect: 方法将被调用。这是你画任何你喜欢的东西的机会。

有一个隐式焦点堆栈，这意味着当您的视图的 drawRect: 被调用时，绘图将被聚焦并剪切到您所在窗口中视图的边界。然后您可以调用诸如 [[NSColor redColor] set 之类的函数];和 NSRectFill([self bounds]);

这是一个例子：

@interface MyView : NSView {
    @private
    NSColor *lineColor; 
    NSInteger clickCount;
}
@end

@implementation MyView
- (void)setLineColor:(NSColor *)color {
    if (color != lineColor) {
        [lineColor release];
        lineColor = [color copy];
        [self setNeedsDisplay:YES]; /// We changed what we'd draw, invalidate our drawing.
    }
}
- (void)mouseDown:(NSEvent *)mouseDown {
    clickCount = (clickCount == 6) ? 0 : (clickCount + 1);
    CGFloat hue = clickCount / 6.0; 
    [self setLineColor:[NSColor colorWithCalibratedHue:hue saturation:1.0 brightness:1.0 alpha:1.0]];
}

- (void)drawRect:(NSRect)dirtyRect {
    NSBezierPath *line = [NSBezierPath bezierPath];
    [line moveToPoint:NSMakePoint(NSMinX([self bounds]), NSMinY([self bounds]))];
    [line lineToPoint:NSMakePoint(NSMaxX([self bounds]), NSMaxY([self bounds]))];
    [line setLineWidth:5.0]; /// Make it easy to see
    [[self lineColor] set]; /// Make future drawing the color of lineColor.
    [line stroke];
}
@end

视图应该画一条对角线，并且每次点击它都会改变颜色。

Answer 3

我尝试了 Jon 给出的示例，发现我需要在上面的代码示例中添加 2 个小修复。

1. 将 NSColor 的分配器插入到 init 块中
2. 更改第二个 moveToPoint 使其变为 lineToPoint

一旦我解决了这个问题，我发现代码片段非常有用。 注意：您可能还需要释放 NSColor。

@interface PropertyPropagateView : NSView {
@private
    NSColor *lineColor; 
    NSInteger clickCount;  
}

@end


@implementation PropertyPropagateView

- (id)initWithFrame:(NSRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        lineColor=[NSColor blueColor];
    }

    return self;
}

- (void)dealloc
{
    [super dealloc];
}

- (void)setLineColor:(NSColor *)color {
    if (color != lineColor) {
        [lineColor release];
        lineColor = [color copy];
        [self setNeedsDisplay:YES]; /// We changed what we'd draw, invalidate our drawing.
    }
}
- (void)mouseDown:(NSEvent *)mouseDown {
    clickCount = (clickCount == 6) ? 0 : (clickCount + 1);
    CGFloat hue = clickCount / 6.0; 
    [self setLineColor:[NSColor colorWithCalibratedHue:hue saturation:1.0 brightness:1.0 alpha:1.0]];
}

- (void)drawRect:(NSRect)dirtyRect
{

    NSBezierPath *line = [NSBezierPath bezierPath];
    [line moveToPoint:NSMakePoint(NSMinX([self bounds]), NSMinY([self bounds]))];
    [line lineToPoint:NSMakePoint(NSMaxX([self bounds]), NSMaxY([self bounds]))];
    [line setLineWidth:5.0]; /// Make it easy to see
    [lineColor set]; /// Make future drawing the color of lineColor.

    [line stroke];
}

@end

Answer 4

只是为了补充一些信息，我养成了确保图形状态在绘制前后保存和恢复的习惯，以保持流畅。

- (void)drawRect:(NSRect)dirtyRect {

    [[NSGraphicsContext currentContext] saveGraphicsState]

    NSBezierPath *line = [NSBezierPath bezierPath];
    [line moveToPoint:NSMakePoint(NSMinX([self bounds]), NSMinY([self bounds]))];
    [line lineToPoint:NSMakePoint(NSMaxX([self bounds]), NSMaxY([self bounds]))];
    [line setLineWidth:5.0]; /// Make it easy to see
    [[self lineColor] set]; /// Make future drawing the color of lineColor.
    [line stroke];

    [[NSGraphicsContext currentContext] restoreGraphicsState]

}