ios – 我可以在drawRect方法之外绘制圆形,矩形,直线等形状

CGContextRef contextRef = UIGraphicsGetCurrentContext();

CGContextRef contextRef = UIGraphicsGetCurrentContext();
CGContextSetRGBFillColor(contextRef,255,1);
CGContextFillEllipseInRect(contextRef,CGRectMake(theMovedPoint.x,theMovedPoint.y,8,8));

基本上你需要一个上下文来绘制一些东西.您可以将上下文视为白皮书.如果您不在有效的上下文中,UIGraphicsGetCurrentContext将返回null.在drawRect中,您将获得视图的上下文.

话虽如此,你可以在drawRect方法之外绘制.您可以开始使用imageContext绘制内容并将其添加到视图中.

请看下面的例子,取自here,

- (UIImage *)imageByDrawingCircLeonImage:(UIImage *)image
{
    // begin a graphics context of sufficient size
    UIGraphicsBeginImageContext(image.sizE);

    // draw original imagE into the context
    [image drawAtPoint:CGPointZero];

    // get the context for CoreGraphics
    CGContextRef ctx = UIGraphicsGetCurrentContext();

    // set stroking color and draw circle
    [[UIColor redColor] setstroke];

    // make circle rect 5 px from border
    CGRect circleRect = CGRectMake(0,image.size.width,image.size.height);
    circleRect = CGRecTinset(circleRect,5,5);

    // draw circle
    CGContextstrokeEllipseInRect(ctx,circleRect);

    // make image out of bitmap context
    UIImage *retImage = UIGraphicsGetImageFromCurrentImageContext();

    // free the context
    UIGraphicsEndImageContext();

    return retImage;
}