在 UIView 内旋转 UIImageView 的奇怪行为

Question

很多相关的问题，但我看不到任何与此完全匹配的问题。

我的应用程序有一个内容视图和一个广告横幅视图。

每次用户旋转设备时，

- (void) layoutSubviews

都会在内容视图上调用。

我的内容视图包含单个图像。我希望该图像随设备一起旋转（它是带纹理的背景，因此我只想将其旋转 90° 或 0°，具体取决于物理设备是纵向还是横向。

代码如下：

//
//  ContentView.m
//  ChordWheel2
//
//  Created by Pi on 16/08/2011.
//  Copyright 2011 Pi. All rights reserved.
//

#import "ContentView.h"


#import "Helper.h"

@implementation ContentView

- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        // Initialization code

        self.autoresizesSubviews = YES;
        {
            // background -- want to cache, so imageNamed is the right method
            UIImage* backgroundImage = [UIImage imageNamed: @"background2.png"];

            background = [[[UIImageView alloc] initWithFrame: frame] autorelease];

            background.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;

            //background.autoresizingMask = 
            [background setImage: backgroundImage];

            [self addSubview: background];
        }
    }
    return self;
}

- (void) layoutSubviews
{
    UIDeviceOrientation O = [UIDevice currentDevice].orientation;

    BOOL is_L = UIInterfaceOrientationIsLandscape( O );

    float theta = is_L ? M_HALF_PI : 0;

    LOG( @"T = %@", NSStringFromCGAffineTransform( background.transform ) ) ;
    LOG( @"C = %@", NSStringFromCGPoint( background.center ) );

    background.transform = CGAffineTransformMakeRotation( theta );
}

@end

现在没有 < code>layoutSubviews 覆盖它，只是挤压图像而不是旋转它。

但是当我放入第二个函数时，它会变得混乱。

这是重复旋转设备的输出日志

T = [1, 0, 0, 1, 0, 0]    C = {160, 240}
T = [1, 0, 0, 1, 0, 0]    C = {240, 160}
T = [0, 1, -1, 0, 0, 0]    C = {160, 240}
T = [1, 0, -0, 1, 0, 0]    C = {240, 160}
T = [0, 1, -1, 0, 0, 0]    C = {320, 80}
T = [1, 0, -0, 1, 0, 0]    C = {400, 0}
T = [0, 1, -1, 0, 0, 0]    C = {320, 80}
T = [1, 0, -0, 1, 0, 0]    C = {400, 0}
T = [0, 1, -1, 0, 0, 0]    C = {320, 80}
T = [1, 0, -0, 1, 0, 0]    C = {480, -80}
T = [0, 1, -1, 0, 0, 0]    C = {400, 0}
T = [1, 0, -0, 1, 0, 0]    C = {640, -80}
T = [0, 1, -1, 0, 0, 0]    C = {560, 0}
T = [1, 0, -0, 1, 0, 0]    C = {800, -80}
T = [0, 1, -1, 0, 0, 0]    C = {720, 0}
T = [1, 0, -0, 1, 0, 0]    C = {960, -80}
T = [0, 1, -1, 0, 0, 0]    C = {880, 0}

。变换出来就是正确地报告中心点。

T = [1, 0, 0, 1, 0, 0]    C = {160, 240}
T = [1, 0, 0, 1, 0, 0]    C = {240, 160}
T = [1, 0, 0, 1, 0, 0]    C = {160, 240}
T = [1, 0, 0, 1, 0, 0]    C = {240, 160}
T = [1, 0, 0, 1, 0, 0]    C = {160, 240}
T = [1, 0, 0, 1, 0, 0]    C = {240, 160}

我想了解发生了什么。

Answer 1

终于明白了。

首先我需要设置

self.autoresizesSubviews = NO;

然后每次方向改变迫使layoutSubviews时我都必须重新居中图像视图：

background.center = self.center;
background.transform = CGAffineTransformMakeRotation( theta );