我不知道从哪里开始。 显然，CGRectIntersectsRect在这种情况下无法使用，您将看到原因。
我有一个UIView的子类，其中包含一个UIImageView，该UIImageView放置在UIView的正中心：
然后我旋转自定义UIView以保持内部UIImageView的框架，同时仍能执行CGAffineRotation。 结果的框架看起来像这样：
我需要防止用户使这些UIImageView相交，但是我不知道如何检查两个UIImageView之间的交点，因为它们的框架不仅不适用于父UIView，而且还会在不影响其框架的情况下旋转。
我的尝试只有失败的结果。
有任何想法吗？
以下算法可用于检查两个（旋转或其他转换的）视图是否重叠：
[view convertPoint:point toView:nil] 将两个视图的 4 个边界点转换为一个公共坐标系（窗口坐标）。这里有另一个描述该算法并包含伪代码的链接：http://www.geometrictools.com/Documentation/MethodOfSeparatingAxes.pdf。通过搜索“分离轴定理”可以找到更多相关信息。
更新：我尝试创建一个 Objective-C 方法来实现“分离轴定理”，以下是我的成果。目前为止，我只进行了一些测试，所以希望没有太多错误。
- (BOOL)convexPolygon:(CGPoint *)poly1 count:(int)count1 intersectsWith:(CGPoint *)poly2 count:(int)count2;
测试两个凸多边形是否相交。两个多边形都作为顶点的 CGPoint 数组给出。
- (BOOL)view:(UIView *)view1 intersectsWith:(UIView *)view2
测试（如上所述）两个任意视图是否相交。
实现：
- (void)projectionOfPolygon:(CGPoint *)poly count:(int)count onto:(CGPoint)perp min:(CGFloat *)minp max:(CGFloat *)maxp
{
CGFloat minproj = MAXFLOAT;
CGFloat maxproj = -MAXFLOAT;
for (int j = 0; j < count; j++) {
CGFloat proj = poly[j].x * perp.x + poly[j].y * perp.y;
if (proj > maxproj)
maxproj = proj;
if (proj < minproj)
minproj = proj;
}
*minp = minproj;
*maxp = maxproj;
}
-(BOOL)convexPolygon:(CGPoint *)poly1 count:(int)count1 intersectsWith:(CGPoint *)poly2 count:(int)count2
{
for (int i = 0; i < count1; i++) {
// Perpendicular vector for one edge of poly1:
CGPoint p1 = poly1[i];
CGPoint p2 = poly1[(i+1) % count1];
CGPoint perp = CGPointMake(- (p2.y - p1.y), p2.x - p1.x);
// Projection intervals of poly1, poly2 onto perpendicular vector:
CGFloat minp1, maxp1, minp2, maxp2;
[self projectionOfPolygon:poly1 count:count1 onto:perp min:&minp1 max:&maxp1];
[self projectionOfPolygon:poly2 count:count1 onto:perp min:&minp2 max:&maxp2];
// If projections do not overlap then we have a "separating axis"
// which means that the polygons do not intersect:
if (maxp1 < minp2 || maxp2 < minp1)
return NO;
}
// And now the other way around with edges from poly2:
for (int i = 0; i < count2; i++) {
CGPoint p1 = poly2[i];
CGPoint p2 = poly2[(i+1) % count2];
CGPoint perp = CGPointMake(- (p2.y - p1.y), p2.x - p1.x);
CGFloat minp1, maxp1, minp2, maxp2;
[self projectionOfPolygon:poly1 count:count1 onto:perp min:&minp1 max:&maxp1];
[self projectionOfPolygon:poly2 count:count1 onto:perp min:&minp2 max:&maxp2];
if (maxp1 < minp2 || maxp2 < minp1)
return NO;
}
// No separating axis found, then the polygons must intersect:
return YES;
}
- (BOOL)view:(UIView *)view1 intersectsWith:(UIView *)view2
{
CGPoint poly1[4];
CGRect bounds1 = view1.bounds;
poly1[0] = [view1 convertPoint:bounds1.origin toView:nil];
poly1[1] = [view1 convertPoint:CGPointMake(bounds1.origin.x + bounds1.size.width, bounds1.origin.y) toView:nil];
poly1[2] = [view1 convertPoint:CGPointMake(bounds1.origin.x + bounds1.size.width, bounds1.origin.y + bounds1.size.height) toView:nil];
poly1[3] = [view1 convertPoint:CGPointMake(bounds1.origin.x, bounds1.origin.y + bounds1.size.height) toView:nil];
CGPoint poly2[4];
CGRect bounds2 = view2.bounds;
poly2[0] = [view2 convertPoint:bounds2.origin toView:nil];
poly2[1] = [view2 convertPoint:CGPointMake(bounds2.origin.x + bounds2.size.width, bounds2.origin.y) toView:nil];
poly2[2] = [view2 convertPoint:CGPointMake(bounds2.origin.x + bounds2.size.width, bounds2.origin.y + bounds2.size.height) toView:nil];
poly2[3] = [view2 convertPoint:CGPointMake(bounds2.origin.x, bounds2.origin.y + bounds2.size.height) toView:nil];
return [self convexPolygon:poly1 count:4 intersectsWith:poly2 count:4];
}
Swift版本。（通过扩展在UIView中添加了此行为）
extension UIView {
func projection(of polygon: [CGPoint], perpendicularVector: CGPoint) -> (CGFloat, CGFloat) {
var minproj = CGFloat.greatestFiniteMagnitude
var maxproj = -CGFloat.greatestFiniteMagnitude
for j in 0..<polygon.count {
let proj = polygon[j].x * perpendicularVector.x + polygon[j].y * perpendicularVector.y
if proj > maxproj {
maxproj = proj
}
if proj < minproj {
minproj = proj
}
}
return (minproj, maxproj)
}
func convex(polygon: [CGPoint], intersectsWith polygon2: [CGPoint]) -> Bool {
//
let count1 = polygon.count
for i in 0..<count1 {
let p1 = polygon[i]
let p2 = polygon[(i+1) % count1]
let perpendicularVector = CGPoint(x: -(p2.y - p1.y), y: p2.x - p1.x)
let m1 = projection(of: polygon, perpendicularVector: perpendicularVector)
let minp1 = m1.0
let maxp1 = m1.1
let m2 = projection(of: polygon2, perpendicularVector: perpendicularVector)
let minp2 = m2.0
let maxp2 = m2.1
if maxp1 < minp2 || maxp2 < minp1 {
return false
}
}
//
let count2 = polygon2.count
for i in 0..<count2 {
let p1 = polygon2[i]
let p2 = polygon2[(i+1) % count2]
let perpendicularVector = CGPoint(x: -(p2.y - p1.y), y: p2.x - p1.x)
let m1 = projection(of: polygon, perpendicularVector: perpendicularVector)
let minp1 = m1.0
let maxp1 = m1.1
let m2 = projection(of: polygon2, perpendicularVector: perpendicularVector)
let minp2 = m2.0
let maxp2 = m1.0
if maxp1 < minp2 || maxp2 < minp1 {
return false
}
}
//
return true
}
func intersects(with someView: UIView) -> Bool {
//
var points1 = [CGPoint]()
let bounds1 = bounds
let p11 = convert(bounds1.origin, to: nil)
let p21 = convert(CGPoint(x: bounds1.origin.x + bounds1.size.width, y: bounds1.origin.y), to: nil)
let p31 = convert(CGPoint(x: bounds1.origin.x + bounds1.size.width, y: bounds1.origin.y + bounds1.size.height) , to: nil)
let p41 = convert(CGPoint(x: bounds1.origin.x, y: bounds1.origin.y + bounds1.size.height), to: nil)
points1.append(p11)
points1.append(p21)
points1.append(p31)
points1.append(p41)
//
var points2 = [CGPoint]()
let bounds2 = someView.bounds
let p12 = someView.convert(bounds2.origin, to: nil)
let p22 = someView.convert(CGPoint(x: bounds2.origin.x + bounds2.size.width, y: bounds2.origin.y), to: nil)
let p32 = someView.convert(CGPoint(x: bounds2.origin.x + bounds2.size.width, y: bounds2.origin.y + bounds2.size.height) , to: nil)
let p42 = someView.convert(CGPoint(x: bounds2.origin.x, y: bounds2.origin.y + bounds2.size.height), to: nil)
points2.append(p12)
points2.append(p22)
points2.append(p32)
points2.append(p42)
//
return convex(polygon: points1, intersectsWith: points2)
}