用手势画线

Question

我使用以下代码添加一个视图作为子视图

    imageview = [[UIImageView alloc] initWithFrame:[holderView frame]];
    [imageview setImage:cppobject->OutputImage];
    imageview.contentMode = UIViewContentModeScaleAspectFit;

    [holderView addSubview:imageview];
    holderView.contentMode = UIViewContentModeScaleAspectFit ;

    UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(scale:)];
    [pinchRecognizer setDelegate:self];
    [holderView addGestureRecognizer:pinchRecognizer];
    [pinchRecognizer release];

    UIRotationGestureRecognizer *rotationRecognizer = [[UIRotationGestureRecognizer alloc] initWithTarget:self action:@selector(rotate:)];
    [rotationRecognizer setDelegate:self];
    [holderView addGestureRecognizer:rotationRecognizer];
    [rotationRecognizer release];

    UIPanGestureRecognizer *panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(move:)];
    [panRecognizer setMinimumNumberOfTouches:1];
    [panRecognizer setMaximumNumberOfTouches:1];
    [panRecognizer setDelegate:self];
    [holderView addGestureRecognizer:panRecognizer];
    [panRecognizer release];

-(void)scale:(id)sender {
}

-(void)rotate:(id)sender {
}

-(void)move:(id)sender {
}

-(void)tapped:(id)sender {
}

，当用户使用两根手指平移时，我需要画线和一个 uilabel （绿色的），如下图所示，

我在 如何在 iPhone 手势中绘制图形？

但我无法将其应用于子视图，特别是 DrawInRect 方法

中的 panRecognizer 函数（移动） 我想使用画线

    UIPanGestureRecognizer *gR = (UIPanGestureRecognizer *) sender ; 
    NSValue *value = [NSValue valueWithCGPoint: [gR locationInView:gR.view]]; 
    [Points addObject:value];
    [holderView setNeedsDisplay];

    NSLog(@"End of measuring") ; 

中的所有子视图上方画线

-(void)drawRect:(CGRect)rect { 
  NSLog(@"Entered Draw In Rect");
  if (Measuring) {
    [[UIColor redColor] setStroke];
    UIBezierPath *pathToDraw = [UIBezierPath bezierPath]; 

    for (int n = 1; n < [Points count] - 1 ; n++) { 
      NSValue * value = [Points objectAtIndex:(NSInteger)n];
      CGPoint  point = [value CGPointValue]; 
      [pathToDraw moveToPoint:point];
      value = [Points objectAtIndex:(NSInteger)n+1];
      point = [value CGPointValue];
      [pathToDraw addLineToPoint:point];
    }
    [pathToDraw stroke];
  }
}

，我将使用 Points 中的点在问题 是 [holderView setNeedsDisplay];切勿致电或触发任何建议或有关

任何建议的帮助

Answer 1

作为子视图的图像视图绘制在持有者视图的顶部。图像视图是不透明的。这意味着当绘制视图时，持有者视图的任何部分实际上都不可见，因此它的 drawRect 调用被优化了。

尝试以相反的方式对视图进行排序，以便持有者视图是图像视图的子视图。然后将绘制图像视图，并在其顶部绘制持有者视图。

另请注意，您应该使用父视图的边界作为子视图的框架。

UIView* subview = [[UIView alloc] initWithFrame:[parentview bounds]];

编辑（添加）：

请参阅http://developer.apple.com/library/ios/#documentation/WindowsViews/Conceptual/ViewPG_iPhoneOS/WindowsandViews/WindowsandViews.html%23//apple_ref/doc/uid/TP40009503-CH2-SW1< /a>
，特别是在“视图层次结构和子视图管理”部分下：

“从视觉上看，子视图的内容掩盖了其父视图的全部或部分内容”

因此，尝试使 imageview 成为父视图，像这样进行初始化：

// instance variables:
UIImageView* imageView;
MyHolderView* holderView;

imageView = [[UIImageView alloc] initWithFrame:mainRect];
holderView = [[MyHolderView alloc] initWithFrame:[imageView bounds]];
holderView.opaque = NO;
holderView.backgroundColor = [UIColor clearColor];
[imageView addSubview:holderView];

UIPinchGestureRecognizer *pinchRecognizer = [[UIPinchGestureRecognizer alloc] initWithTarget:holderView action:@selector(scale:)];
[pinchRecognizer setDelegate:self];
[holderView addGestureRecognizer:pinchRecognizer];
[pinchRecognizer release];

// etc...

现在，绘制图像视图，并在其之上绘制持有者视图及其子视图。现在，当您在 HolderView 上调用 setNeedsDisplay 时，它将收到 drawRect: 调用。

例如，像这样跟踪手势。这可能位于您的视图控制器或 MyHolderView 视图子类中；这里的示例位于 MyHolderView 类中，以便可以使用 drawRect: 方法轻松共享 location1 和 location2 实例变量。

-(void)scale:(id)sender {
  if (sender == pinchRecognizer) { // this allows the responder to work with multiple gestures if required
    // get position of touches, for example:
    NSUInteger num_touches = [pinchRecognizer numberOfTouches];

    // save locations to some instance variables, like `CGPoint location1, location2;`
    if (num_touches >= 1) {
      location1 = [pinchRecognizer locationOfTouch:0 inView:holderView];
    }
    if (num_touches >= 2) {
      location2 = [pinchRecognizer locationOfTouch:1 inView:holderView];
    }

    // tell the view to redraw.
    [holderView setNeedsDisplay];
  }
}

：然后在持有者视图中绘制矩形例程：

-(void)drawRect:(CGRect)rect {

  // use instance variables location1 and location2 to draw the line.
}