在视图中拖动视图，将其限制在
我有一段非常简单的用于拖动和绘图的代码。
三个视图：根视图基本上是窗口（带有一些界面控件）。 在其中，我有一个“画布”视图。在画布视图中，我有第三个视图（角色的小图形），用户可以在画布内“拖动”该视图。拖动效果很好。
问题是我似乎无法将我的“角色”限制在画布的范围内。理想情况下，当他跑到画布边缘时，他应该停下来（不要溢出到根视图中）。
画布视图会剪辑子视图；所以一旦他越过边缘，他就会消失——但我不希望他消失，我希望他不能再走得更远。
我还在动画之前调用 CGRectIsWithinRect ，原则上应该可以解决问题。问题在于，动画发生时角色的框架不会更新 - 因此只要他已经在移动，他就会继续在页面右侧移动。
-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UIView * charView = [[canvasView floatingView] retain];
CGPoint pt = [[touches anyObject] locationInView:canvasView];
if (CGRectContainsPoint([canvasView bounds], pt)) {
CGRect charFrame = charView.frame;
CGRect containerFrame = canvasView.frame;
BOOL inTheYard= CGRectContainsRect(containerFrame, charFrame);
if (inTheYard == NO) {
//if we're at the edge, don't go any further
return;
}
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationDuration:.2];
CGFloat x = floatingView.center.x + (pt.x - startPoint.x);
CGFloat y = floatingView.center.y + (pt.y - startPoint.y);
CGPoint middle = CGPointMake(x,y);
floatingView.center = middle;
[UIView commitAnimations];
[floatingView release];
}
}
我怎样才能阻止他超越他的超级视图的边缘？
I have a pretty simple bit of code for dragging and drawing.
Three views: The root view is basically the window (with a few interface controls).
Within it, I have a "canvas" view. Within the canvas view, I have a third view (a small graphic of a character), which the user is meant to "drag" around within the canvas. The dragging works fine.
The problem is that I can't seem to constrain my "character" within the bounds of the canvas. Ideally, when he runs into the edge of the canvas, he should stop (not spill over into the root view)
The canvas view clips subviews; so he does disappear once he goes over the edge - but I don't want him to disappear, I want him to not be able to go any further.
I also call CGRectIsWithinRect before my animation, which in principle should do the trick. The problem is that the frame of the character isn't updated while the animation is occurring - so as long as he's already moving, he'll keep on moving right of the side of the page.
-(void) touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
UIView * charView = [[canvasView floatingView] retain];
CGPoint pt = [[touches anyObject] locationInView:canvasView];
if (CGRectContainsPoint([canvasView bounds], pt)) {
CGRect charFrame = charView.frame;
CGRect containerFrame = canvasView.frame;
BOOL inTheYard= CGRectContainsRect(containerFrame, charFrame);
if (inTheYard == NO) {
//if we're at the edge, don't go any further
return;
}
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
[UIView setAnimationDuration:.2];
CGFloat x = floatingView.center.x + (pt.x - startPoint.x);
CGFloat y = floatingView.center.y + (pt.y - startPoint.y);
CGPoint middle = CGPointMake(x,y);
floatingView.center = middle;
[UIView commitAnimations];
[floatingView release];
}
}
How can I keep him from moving past the edges of his superview?
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您可以将其夹在画布内部，而不是检查触摸事件是否在画布内部。分别检查触摸事件的 x 和 y 点，如果它们位于画布之外，则将角色向上移动到画布那一侧的墙壁上。
这将允许您继续沿画布壁拖动角色，即使触摸事件位于外部（如果您删除 inTheYard 检查）。
Instead of checking if the touch event is inside the canvas you can clamp it to be inside. Check the x and y points for the touch event separately and if they are outside the canvas move the character up to the wall on that side of the canvas.
This will allow you to keep dragging the character along the wall of the canvas even when the touch event is outside (if you remove the inTheYard check).