我正在尝试为我的Mac应用程序绘制一个圆圈。守则是:
- (void)mouseMoved:(NSEvent*)theEvent {
NSPoint thePoint = [[self.window contentView] convertPoint:[theEvent locationInWindow] fromView:nil];
NSLog(@"mouse moved: %f % %f",thePoint.x, thePoint.y);
CGRect circleRect = CGRectMake(thePoint.x, thePoint.y, 20, 20);
CGContextRef context = [[NSGraphicsContext currentContext] graphicsPort];
CGContextSetRGBFillColor(context, 0, 0, 255, 1.0);
CGContextSetRGBStrokeColor(context, 0, 0, 255, 0.5);
CGContextFillEllipseInRect(context, CGRectMake(circleRect.origin.x, circleRect.origin.y, 25, 25));
CGContextStrokeEllipseInRect(context, circleRect);
[self needsDisplay];
}
完全调用 - (void)mouseMoved:
,我可以在NSLog中看到正确的x和y坐标。但我没有得到任何圈子......令人惊讶的是:如果我最小化我的应用程序并重新打开它(所以它“更新”NSView)圈子完美绘制!
答案 0 :(得分:4)
mouseMoved
不正确的位置来绘制任何内容,除非您正在绘制到屏幕外缓冲区。如果您要在屏幕上绘图,保存 thePoint 以及任何其他必要数据,请致电[self setNeedsDisplay:YES]
并使用drawRect:(NSRect)rect
方法进行绘制。
另外,在有更多“友好”CGContextRef
的情况下,我无法看到使用NSGraphicsContext
的原因。虽然,这是品味的问题。
绘图代码示例:
- (void)mouseMoved:(NSEvent*)theEvent {
// thePoint must be declared as the class member
thePoint = [[self.window contentView] convertPoint:[theEvent locationInWindow] fromView:nil];
[self setNeedsDisplay:YES];
}
- (void)drawRect:(NSRect)rect
{
NSRect ovalRect = NSMakeRect(thePoint.x - 100, thePoint.y - 100, 200, 200);
NSBezierPath* oval = [NSBezierPath bezierPathWithOvalInRect:ovalRect];
[[NSColor blueColor] set];
[oval fill];
[[NSColor redColor] set];
[oval stroke];
}