在NSView-drawRect:方法中绘制直线的首选/推荐方法是什么？

Question

我在NSView级别的Cocoa中找不到任何线条图原语.我唯一能找到的是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正是你应该使用的.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,将调用视图的drawRect:方法.这是你画出任何你喜欢的东西的机会.

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它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]);

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

视图应绘制一条对角线,每次单击该线时,该线应改变颜色.