如何使用 UIBezierPath 绘制平滑直线？

Question

我希望能够使用 UIBezierPath 在 iPad 屏幕上绘制直线。我该怎么办呢？

我想做的是这样的：双击屏幕来定义起点。一旦我的手指位于屏幕上方，直线就会随着我的手指移动（这应该恰好弄清楚我应该将下一个手指放在哪里，以便它会创建一条直线）。然后，如果我再次双击屏幕，则会定义终点。

此外，如果我双击终点，则应开始新行。

是否有任何可用资源可供我使用以提供指导？

Answer 1

UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:startOfLine];
[path addLineToPoint:endOfLine];
[path stroke];

UIBezierPath 类参考

编辑

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Create an array to store line points
    self.linePoints = [NSMutableArray array];

    // Create double tap gesture recognizer
    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];
    [doubleTap setNumberOfTapsRequired:2];
    [self.view addGestureRecognizer:doubleTap];
}

- (void)handleDoubleTap:(UITapGestureRecognizer *)sender
{
    if (sender.state == UIGestureRecognizerStateRecognized) {

        CGPoint touchPoint = [sender locationInView:sender.view];

        // If touch is within range of previous start/end points, use that point.
        for (NSValue *pointValue in linePoints) {
            CGPoint linePoint = [pointValue CGPointValue];
            CGFloat distanceFromTouch = sqrtf(powf((touchPoint.x - linePoint.x), 2) + powf((touchPoint.y - linePoint.y), 2));
            if (distanceFromTouch < MAX_TOUCH_DISTANCE) {    // Say, MAX_TOUCH_DISTANCE = 20.0f, for example...
                touchPoint = linePoint;
            }
        }

        // Draw the line:
        // If no start point yet specified...
        if (!currentPath) {
            currentPath = [UIBezierPath bezierPath];
            [currentPath moveToPoint:touchPoint];
        }

        // If start point already specified...
        else { 
            [currentPath addLineToPoint:touchPoint];
            [currentPath stroke];
            currentPath = nil;
        }

        // Hold onto this point
        [linePoints addObject:[NSValue valueWithCGPoint:touchPoint]];
    }
}

我不会在没有金钱补偿的情况下编写任何少数派报告式的相机魔法代码。