iOS AnchorPoint 引起的坐标问题

这里主要讨论设置AnchorPoint 改变时，会影响我们预期的布局问题；

一、初始代码布局

//参照页面

UIView *aView = [[UIView alloc]initWithFrame:CGRectMake(50, 50, 100, 100)];

aView.backgroundColor = [UIColor redColor];

[self.view addSubview:aView];

UIView *bView = [[UIView alloc]initWithFrame:CGRectMake(150, 50, 100, 100)];

bView.backgroundColor = [UIColor blueColor];

[self.view addSubview:bView];

运行效果如下（默认anchorPoint(0.5,0.5)）

其中 B 坐标信息 :

frame : (origin = (x = 150, y = 50), size = (width = 100, height = 100))

center :(x = 200, y = 100)

二、更改B页面 anchorPoint为（0,0.5）

    bView.layer.anchorPoint = CGPointMake(0.0, 0.5);

运行，结果如下：

B 坐标信息如下

frame : (origin = (x = 200, y = 50), size = (width = 100, height = 100))

center : (x = 200, y = 100)

和“一 ”中结果相比发现，center不变， x坐标向右移动了50pt；

三、更改B页面 anchorPoint为（0.0,0.0）

    bView.layer.anchorPoint = CGPointMake(0.0, 0.0);

运行，结果如下：

B 坐标信息如下

frame : (origin = (x = 200, y = 100), size = (width = 100, height = 100))

center : (x = 200, y = 100)

此时发现 origin 和center重叠了

四、结论

我们设置anchorPoint 时已经改变了我们的布局，这不是我们所期望的；

从二、三运行结果可以发现一下结论：

center坐标的值都未改变。
center 点即使我们的锚点
我们改变锚点值时，页面会相对于原中心点进行相应改变

五、解决方案

那么我们如何想要得到：只设定anchorPoint值，而不影响页面布局呢？答案是，重新计算frame值；

代码如下：

/**设置锚点，且不影响之前的预期布局@param anchorPoint 锚点值如：{1,0.5}@param view 要更改的view*/
- (void)setViewAnchorPoint:(CGPoint)anchorPoint forView:(UIView*)view {CGPoint originAnchorPoint = view.layer.anchorPoint;CGPoint offetPoint = CGPointMake(anchorPoint.x - originAnchorPoint.x, anchorPoint.y - originAnchorPoint.y);CGFloat offetX =  (offetPoint.x)*view.frame.size.width;CGFloat offetY =  (offetPoint.y)*view.frame.size.height;view.layer.anchorPoint = anchorPoint;//设置这个值 说明已经改变了便宜量view.layer.position = CGPointMake(view.layer.position.x + offetX, view.layer.position.y + offetY);//将指定的偏宜量更改回来
}

那么我们设置需要更改的B页面如下调用即可：

    UIView *bView = [[UIView alloc]initWithFrame:CGRectMake(150, 50, 100, 100)];_bView = bView;bView.backgroundColor = [UIColor blueColor];   [self setViewAnchorPoint:CGPointMake(1, 1) forView:bView];//只是测试多次连续设置结果[self setViewAnchorPoint:CGPointMake(0, 0.5) forView:bView];[self.view addSubview:bView];

完美结局

转载于:https://www.cnblogs.com/kingbo/p/7162364.html