用手势画线

Question

我使用以下代码将视图添加为子视图

    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 {
}

当用户用他的两根手指平移和一个 uilabel（绿色的）时，我需要画线，如下图所示

我看过How to draw graphics in iphone gesture?

但我不能将它应用到子视图上，特别是 DrawInRect 方法

在 panRecognizer 函数中（移动）我想画线使用

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

    NSLog(@"End of measuring") ; 

我将使用Points中的点在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];
  }
}

问题是[holderView setNeedsDisplay]；永远不要打电话或解雇 drawRect 任何关于此的建议或帮助

任何建议

Answer 1

作为子视图的图像视图绘制在持有者视图之上。图像视图是不透明的。这意味着在绘制视图时，没有实际可见的持有者视图的任何部分，因此优化了 drawRect 调用。

尝试以相反的方式对视图进行排序，以使持有者视图成为图像视图的子视图。然后 imageview 会绘制，holder view 会在它上面绘制。

另外，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）：

见http://developer.apple.com/library/ios/#documentation/WindowsViews/Conceptual/ViewPG_iPhoneOS/WindowsandViews/WindowsandViews.html%23//apple_ref/doc/uid/TP40009503-CH2-SW1 ，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”

所以，尝试将 imageview 设为父级，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，图像视图被绘制，持有者视图，它的子视图被绘制在它上面。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。这可能在您的视图控制器或您的 MyHolderView 视图子类中；此处的示例将在 MyHolderView 类中，以便 location1 和 location2 实例变量可以轻松地与 drawRect: 方法共享。：

-(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holder视图中drawRect例程：

-(void)drawRect:(CGRect)rect {

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