在mainView上应用变换后如何获取子视图的框架? [英] How to get frame of subview after apply transform on mainView?

问题描述

我已经创建了 UIView 的 mainView 对象并在其上添加了一个子视图.我在 mainView 上应用了变换以减小帧大小.但是mainView的subview的frame没有减少.如何减小此子视图的大小.

I have created mainView objcet of UIView and added one subview on it. I applied transform on mainView for reducing frame size. But frame of subview of mainView was not reduced. How to reduce the size of this subview.

- (void)viewDidLoad
{
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    CGFloat widthM=1200.0;
    CGFloat heightM=1800.0;
    UIView *mainView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, widthM, heightM)];
    mainView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"te.png"]];
    [self.view addSubview:mainView];
    CGFloat yourDesiredWidth = 250.0;
    CGFloat yourDesiredHeight = yourDesiredWidth *heightM/widthM;
    CGAffineTransform scalingTransform;
    scalingTransform = CGAffineTransformMakeScale(yourDesiredWidth/mainView.frame.size.width, yourDesiredHeight/mainView.frame.size.height);
     mainView.transform = scalingTransform;
    mainView.center = self.view.center;
    NSLog(@"mainView:%@",mainView);
    UIView *subMainView= [[UIView alloc] initWithFrame:CGRectMake(100, 100, 1000, 1200)];
    subMainView.backgroundColor = [UIColor redColor];
    [mainView addSubview:subMainView];
    NSLog(@"subMainView:%@",subMainView);

}

这些视图的 NSlog:

NSlog of these views:

mainView:<UIView: 0x8878490; frame = (35 62.5; 250 375); transform = [0.208333, 0, 0, 0.208333, 0, 0]; layer = <CALayer: 0x8879140>>
subMainView:<UIView: 0x887b8c0; frame = (100 100; 1000 1200); layer = <CALayer: 0x887c160>>

这里mainView的宽度为250，subview的宽度为1000.但是当我在模拟器中得到输出时，subview被正确占用，但它没有穿过mainView.怎么可能?转换后如何获取相对于mainView框架的subview框架?

Here the width of mainView is 250, the width of subview is 1000. but when i get the output in simulator, subview is occupied correctly, but it's not cross the mainView. How it is possible? How to get frame of subview with respect mainView frame after transformation?

推荐答案

您看到的是预期行为.UIView 的框架是相对于它的父视图的，所以当你对它的父视图应用转换时它不会改变.虽然视图也会出现扭曲"，但框架不会反映更改，因为它相对于其父级仍然处于完全相同的位置.
但是，我假设您希望获得相对于最顶层 UIView 的视图框架.在这种情况下，UIKit 提供了以下功能:

What you're seeing is expected behavior. The frame of an UIView is relative to its parent, so it doesn't change when you apply a transformation to its superview. While the view will appear 'distorted' too, the frame won't reflect the changes since it's still at exact the same position relative to its parent.
However, I assume you would like to get the frame of the view relative to the topmost UIView. In that case UIKit offers these functions:

• – [UIView convertPoint:toView:]
• – [UIView convertPoint:fromView:]
• – [UIView convertRect:toView:]
• – [UIView convertRect:fromView:]

我将这些应用于您的示例:

I applied these to your example:

CGRect frame = [[self view] convertRect:[subMainView frame] fromView:mainView];
NSLog(@"subMainView:%@", NSStringFromCGRect(frame));

这是输出:

subMainView:{{55.8333, 83.3333}, {208.333, 250}}

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