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我正在使用此代码绘制一条直线（显然在用户触摸时），我需要从起点显示直线，直到用户从起点开始触摸（未结束触摸），就像橡皮筋一样，跟随手指移动。我可能忽略了一些我需要修改以产生必要效果的东西。任何想法？

注意：我在视图控制器内。

- (void) drawLine:(UIPanGestureRecognizer *)sender
{

    NSLog(@"Sender : %@", sender);
    CGPoint currentPoint;

    //CGAffineTransformMakeScale(lastScale, lastScale);
    if([(UIPanGestureRecognizer *)sender state] == UIGestureRecognizerStateBegan ||                                       [(UIPanGestureRecognizer *)sender state] == UIGestureRecognizerStateChanged)
    {
        currentPoint = [(UIPanGestureRecognizer *)sender locationInView:imgView];

        previousPoint = currentPoint;
    }

    if([(UIPanGestureRecognizer *)sender state] == UIGestureRecognizerStateChanged) 
    { 
        touchedPoint = [(UIPanGestureRecognizer *)sender locationInView:imgView]; 
        [imgView setNeedsDisplay]; 
    }

    if([(UIPanGestureRecognizer *)sender state] == UIGestureRecognizerStateEnded)
    {
        currentPoint = [(UIPanGestureRecognizer *)sender locationInView:imgView];
        imgView.image =  [self drawLineFromPoint:previousPoint toPoint:currentPoint   image:imgView.image];

        previousPoint = currentPoint;

    }

}

这是 [drawline frompoint: topoint:] 方法

UIGraphicsBeginImageContext(imgView.frame.size);
CGContextRef context = UIGraphicsGetCurrentContext();       
CGContextSaveGState(context);

CGContextTranslateCTM(context, 0.0, imgView.frame.size.height);
CGContextScaleCTM(context, 1.0, -1.0);

CGContextSetShouldAntialias(context, YES);
CGContextSetLineWidth(context, 1.0f);
CGContextSetRGBStrokeColor(context, 0.7, 0.7, 0.7, 1.0);

CGContextMoveToPoint(context, fromPoint.x, fromPoint.y);
CGContextAddLineToPoint(context, toPoint.x, toPoint.y);
CGContextDrawPath(context, kCGPathStroke); 

CGContextRestoreGState(context);

NSLog(@"frompoint.x : %f, frompoint.y : %f",fromPoint.x, fromPoint.y );
NSLog(@"topoint.x : %f, topoint.y : %f", toPoint.x, toPoint.y);

UIImage *ret = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
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1 回答 1

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DrawingApp这是我发现的一个示例项目，它可以满足您的需求。

另一种方法是，正如 Lefteris 在评论中建议的那样，在 UIView 内部，覆盖触摸开始、移动和结束。并使用 drawRect 画线。该线将拖动到您当前触摸的任何位置。

于 2012-09-22T04:07:18.060 回答