在 NSView-drawRect: 方法中绘制线条的首选/推荐方法是什么？

Question

我在 Cocoa 的 NSView 级别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？还是还有其他我没发现的方法？

Answer 1

NSBezierPath 正是您应该使用的。如果您只想从一个点到另一个点绘制一条直线，请使用类方法：

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

Answer 2

Cocoa 使用隐式绘图堆栈和失效模型。在你的 NSView 中，当状态改变导致视图以不同的方式绘制时，你调用 -[self setNeedsDisplay:] 来告诉绘图系统你需要重新绘制。在不久的将来的某个时刻，实际上是当前事件循环的结束，您的视图的drawRect：方法将被调用。这是你画任何你想画的东西的机会。

有一个隐式焦点堆栈，这意味着当调用视图的drawRect:时，绘图将集中在其所在窗口中的视图边界上并剪切到视图的边界。然后，您可以调用诸如 [[NSColor redColor] set]; 之类的函数和 NSRectFill([自身边界]);

下面是一个示例：

@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

视图应绘制一条对角线，每次单击该对角线时，该线都应改变颜色。

Answer 3

我尝试了 Jon 给出的示例，发现我需要对上面的代码示例添加 2 个小修复。

1. 将 NSColor 的分配器插入 init 块中，
2. 更改第二个 moveToPoint ，使其成为 lineToPoint

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

只是为了添加一些信息，我养成了确保在绘制之前和之后保存和恢复图形状态的习惯，以保持工作顺利。

- (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]

}