在NSView-drawRect：方法中绘制直线的首选/推荐方法是什么？

Question

我无法在NSView级别的可可中找到任何线条绘制图元。我唯一发现的是NSBezierPath。这是一个首选的方式？还是有另一种我无法发现的方式？

Answer 1

Cocoa使用隐式绘图堆栈和无效模型。在你的NSView中，当状态改变会导致视图绘制不同时，你调用 - [self setNeedsDisplay：]告诉绘图系统你需要重画。在不久的将来，实际上是当前事件循环的结尾，您的视图的drawRect：方法将被调用。这是你绘制任何你想要的东西的机会。

有一个隐含的焦点堆栈，这意味着当您调用view的drawRect：时，绘图会聚焦在您的视图的边界上并将其剪裁到其所在的窗口中。然后可以调用函数，如[[NSColor redColor]组];和NSRectFill（[自我界限]）;

下面是一个例子：

@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 

的视图应该绘制一条对角线，它被点击，每次行应该改变颜色。

Answer 2

NSBezierPath正是你应该使用的。如果你只是想从一个点绘制一条直线到另一个，使用类方法：

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

Answer 3

我试图通过乔恩给出的例子，我发现我需要2条小的修改添加到代码示例以上。

1. ，使之成为一个lineToPoint

一旦我固定这一点，我发现代码片段非常有用的插入NSColor的分配器到初始块

改变第二moveToPoint。 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，我习惯于确保图形状态在绘制之前和之后保存和恢复，以保持活动的活力。

- (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] 

}