如何在iPhone中用CAShapeLayer绘制45度角直线

Question

我可以使用CAShapeLayer绘制直线，但我尝试仅以45度角绘制一条直线。直线必须以45度角绘制，否则它将从视图中删除，我如何使用CAShapeLayer绘制直线，请帮助。下面是我绘制线条的代码：

- (void)handlePanGesture:(UIPanGestureRecognizer *)gesture
{
 static CGPoint origin;
 CGPoint location ;
 if (gesture.state == UIGestureRecognizerStateBegan)
{
  shapeLayer = [self createShapeLayer:gesture.view];
  origin = [gesture locationInView:gesture.view];
  UIView *tappedView = [gesture.view hitTest:origin withEvent:nil];
  UILabel *tempLabel = (UILabel *)tappedView;
  [valuesArray addObject:tempLabel];

  if(valuesArray)
  {
      [valuesArray removeAllObjects];
  }
  valuesArray = [[NSMutableArray alloc] init];
 }
 else if (gesture.state == UIGestureRecognizerStateChanged)
 {
       path1 = [UIBezierPath bezierPath];
       [path1 moveToPoint:origin];
       location = [gesture locationInView:gesture.view];
      [path1 addLineToPoint:location];
      shapeLayer.path = path1.CGPath;
}
}

- (CAShapeLayer *)createShapeLayer:(UIView *)view
{
shapeLayer = [[CAShapeLayer alloc] init];
shapeLayer.fillColor = [UIColor clearColor].CGColor;
shapeLayer.strokeColor = [UIColor redColor].CGColor;
shapeLayer.lineCap = kCALineCapRound;
shapeLayer.lineJoin = kCALineJoinRound;
shapeLayer.lineWidth = 10.0;
[view.layer addSublayer:shapeLayer];//view.layer

return shapeLayer;
}

Answer 1

据我所知，你只需要检查location和origin之间的角度是否为45度正负。因此，您的代码可能如下所示：

// EPSILON represent the acceptable error in pixels
#define EPISLON 2

// ...

else if (gesture.state == UIGestureRecognizerStateChanged)
{
    path1 = [UIBezierPath bezierPath];
    [path1 moveToPoint:origin];

    location = [gesture locationInView:gesture.view];

    // only add the line if the absolute different is acceptable (means less than EPSILON)
    CGFloat dx = (location.x - origin.x), dy = (location.y - origin.y);
    if (fabs(fabs(dx) - fabs(dy)) <= EPISLON) {
        [path1 addLineToPoint:location];
        shapeLayer.path = path1.CGPath;
    }
}