Question

我在NSView级别的Cocoa中找不到任何线条图原语。我找到的唯一一件事是NSBezierPath。这是首选方式吗？还是有另一种我无法发现的方式？

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NSView中，当状态更改会导致视图绘制方式不同时，您调用 - [self setNeedsDisplay：]告诉绘图系统您需要重绘。在不久的将来的某个时刻，实际上是当前事件循环的结束，将调用您的视图的drawRect：方法。这是你抽出任何你想要的东西的机会。

有一个隐含的焦点堆栈，这意味着当你的视图的drawRect：被调用时，绘图会聚焦并剪切到你所在窗口中视图的边界。然后你可以调用像[[NSColor redColor] set]这样的函数;和NSRectFill（[self bounds]）;

以下是一个例子：

@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

视图应绘制一条对角线，每次单击该线条时，该线条应改变颜色。

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个小修补程序。

将NSColor的分配器插入init块
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snippit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

只是为了添加一些信息，我养成了确保在绘图前后保存和恢复图形状态的习惯，以保持活力。

- (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]

}

在NSView-drawRect：方法中绘制直线的首选/推荐方法是什么？

4 个答案: