Question

我尝试根据用户触摸在两个点之间添加线（起点将是用户的第一个触摸和终点将是用户在视图上的第二次触摸）.I能够使用下面的代码绘制它。

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    UITouch *touch = [touches anyObject];
    if ([touch tapCount] == 2)
    {
        NSLog(@"touch count 2");
        return;
    }
    if(isOdd)//View already has user's start point
    {
        nextPoint = [touch locationInView:self.view];
        point2 = nextPoint;
        //nextPoint.y -= 20;
        [self drawLineFromPoint:currentPoint toPoint:nextPoint];
        currentPoint = nextPoint;
        NSLog(@"x:%f,y:%f",currentPoint.x,currentPoint.y);
        isOdd = YES;
    }
    else
    {
        currentPoint = [touch locationInView:self.view];
        point1 = currentPoint;
        NSLog(@"x:%f,y:%f",currentPoint.x,currentPoint.y);
        isOdd = YES;
    }
}
-(void)drawLineFromPoint:(CGPoint)start toPoint:(CGPoint)end
{
    UIBezierPath *path = [UIBezierPath new];
    [path moveToPoint:start];
    [path addLineToPoint:end];
    CAShapeLayer *shapeLayer = [CAShapeLayer new];
    shapeLayer.path = path.CGPath;
    shapeLayer.strokeColor = [UIColor greenColor].CGColor;
    shapeLayer.lineWidth = 3.0;
    [self.myView.layer addSublayer:shapeLayer];
}

现在我的问题是，当用户尝试使用手指拖动/移动该线时，是否可以弯曲该线？

Answer 1

如果您的问题是绘制已经绘制的线条，那么您可以尝试以下方法：

如您所知，该线的起点和终点，您可以在手指移动时重绘曲线

  current => head_ref
  prev    => NULL;
  current => head_ref;
  next    => null;
  while (current != NULL)
  {
        next  = current->next;  
        current->next = prev;   
        prev = current;
        current = next;
  }
 *head_ref = prev;

UIBezierPath的功能，其中控制点将是移动期间的当前触摸点。在使用

调用此函数之前，您必须移动到起点

- addQuadCurveToPoint:controlPoint:

并将终点作为上述曲线函数的目标点。

Answer 2

使用CAShapeLayer在A点（startingPoint）和B点（endingPoint）之间画一条直线。

@interface ViewController()
{
   CGFloat startingPoint,endingPoint;
}
@end

@implementation ViewController()

    - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
    {
        UITouch *touch = [[event allTouches] anyObject];
        //Take the first point A from touch began
        startingPoint = [touch locationInView:baseHolderView];

    }
    - (void)touchesEnded:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
    {
        UITouch *touch = [touches anyObject];
        endingPoint = [touch locationInView:baseHolderView];
        //Take the Second point b from touch Ended
        [self makeLineLayer:baseHolderView.layer lineFromPointA:startingPoint toPointB:endingPoint];
    }

    -(void)makeLineLayer:(CALayer *)layer lineFromPointA:(CGPoint)pointA toPointB:(CGPoint)pointB
    {
        CAShapeLayer *line = [CAShapeLayer layer];
        UIBezierPath *linePath=[UIBezierPath bezierPath];
        [linePath moveToPoint: pointA];
        [linePath addLineToPoint:pointB];
        line.path=linePath.CGPath;
        line.fillColor = nil;
        line.opacity = 2.0;
        line.strokeColor = [UIColor blackColor].CGColor;
        [layer addSublayer:line];
    }

@end

在iOS中绘制两条点之间的线并使用手指拖动/曲线该线？

2 个答案: