convertRect

// 将像素point由point所在视图转换到目标视图view中，返回在目标视图view中的像素值
- (CGPoint)convertPoint:(CGPoint)point toView:(UIView *)view;

// 将像素point从view中转换到当前视图中，返回在当前视图中的像素值
- (CGPoint)convertPoint:(CGPoint)point fromView:(UIView *)view;

// 将rect由rect所在视图转换到目标视图view中，返回在目标视图view中的rect
- (CGRect)convertRect:(CGRect)rect toView:(UIView *)view;

// 将rect从view中转换到当前视图中，返回在当前视图中的rect
- (CGRect)convertRect:(CGRect)rect fromView:(UIView *)view;

例子：先创建view1和view2

    UIView *view1 = ({
       
        UIView *view = [[UIView alloc] init];
        view.frame = CGRectMake(20, 100, 300, 200);
        view.backgroundColor = [UIColor redColor];
        
        view;
        
    });
    
    UIView *view2 = ({
        
        UIView *view = [[UIView alloc] init];
        view.frame = CGRectMake(30, 110, 100, 100);
        view.backgroundColor = [UIColor blueColor];
        
        view;
        
    });
    //把view1加在self.view上，把view2加在view1上
    [self.view addSubview:view1];
    [view1 addSubview:view2];

1.png

convertRect

    //目标：算出view2在self.view上frame
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    CGRect view2Rect = view2.frame;
    NSLog(@"%@", NSStringFromCGRect(view2Rect));  //{{30, 110}, {100, 100}}

   //使用convertRect:toView
    //1. 使用view2的superview 来调用，那么要传的rect为view2.frame
    CGRect view2WinodwRect1 = [view2.superview convertRect:view2.frame toView:self.view];
    NSLog(@"%@", NSStringFromCGRect(view2WinodwRect1));//{{50, 210}, {100, 100}}
    
    //2. 使用view2自己来调用，那么要传的rect为view2.bounds；
    //如果传入view2.frame，系统则会多计算出view2在他的superview中的x和y，
    //最后结果就是 x = 2 * view2.superview.x + view2.x , y =  2 * view2.superview.y + view2.y
    CGRect view2WinodwRect2 = [view2 convertRect:view2.bounds toView:self.view];
    NSLog(@"%@", NSStringFromCGRect(view2WinodwRect2));//{{50, 210}, {100, 100}}

    //使用convertRect:fromView
    //3.
    CGRect view2WinodwRect3 = [self.view convertRect:view2.frame fromView:view2.superview];
    NSLog(@"%@", NSStringFromCGRect(view2WinodwRect3));//{{50, 210}, {100, 100}}

    //4.
    CGRect view2WinodwRect4 = [self.view convertRect:view2.bounds fromView:view2];
    NSLog(@"%@", NSStringFromCGRect(view2WinodwRect4));//{{50, 210}, {100, 100}}

  ### 注意点：
   toView: nil 和 fromView:nil  的参数为nil的时候默认是keyWindow，但是要注意keyWindow是否为null，
   当没有在AppDelegate中创建self.window的时候，获取[UIApplication sharedApplication].keyWindow的时候    
   可能为null。