iOS應用程序：定位後調整圖像的尺寸

Question

因爲我確定我的答案已經存在，所以我會事先致歉，但在嘗試了很多建議之後，我似乎無法讓我的應用程序正常工作。

基本上，我想以相同的比例顯示一個16x9的圖像到屏幕中央的全部寬度。與縱向相比，橫向的圖像將更大。我可以顯示圖像，但是當我的Ipad旋轉到縱向時，它會剪切圖像的兩側，使圖像保持原始高度。我沒有使用佈局編輯器，並且不希望爲我的第一個應用程序。圖像使用下面的代碼加載。

viewController.h：

@interface ViewController : UIViewController 
{ 
    UIImageView* MobileImage; // image on mobile device 
} 
@property (nonatomic, retain) UIImageView* MobileImage; 
@end 

viewController.m：

#import "ViewController.h" 

@interface ViewController() 
@end 

@implementation ViewController 

@synthesize MobileImage; 

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    CGFloat width = self.view.bounds.size.width; 
    CGFloat height = width * 9/16; 
    if (height > self.view.bounds.size.height) { // just in case 
     height = self.view.bounds.size.height; 
     width = height * 16/9; 
    } 
    self.MobileImage = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, width, height)]; 
    self.MobileImage.image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"sandy-ralph" ofType:@"png"]]; 
    self.MobileImage.center = self.view.center; 
    self.MobileImage.autoresizingMask = UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin; 
    self.MobileImage.autoresizesSubviews = YES; 

    [self.view addSubview:self.MobileImage]; 
} 

- (void)didReceiveMemoryWarning { 
    [super didReceiveMemoryWarning]; 
    // Dispose of any resources that can be recreated. 
} 

@end 

這工作得很好，如果我不關心剪輯（假設我在景觀開始​​，旋轉爲縱向）。我插入我試圖調整它下面的代碼到執行的viewController：

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator 
{ 
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator]; 

    NSLog(@"Transition to size = %@", NSStringFromCGSize(size)); 
    CGFloat width = size.width; 
    CGFloat height = width * 9/16; 
    if (height > size.height) { // just in case 
     height = size.height; 
     width = height * 16/9; 
    } 

#if 1 // this code has no effect on the image size 
    NSLog(@"Using UIGraphicsGetImageFromCurrentImageContext"); 
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(width, height), NO, 0.0); 
    CGContextRef context = UIGraphicsGetCurrentContext(); 
    UIGraphicsPushContext(context); 
    [self.MobileImage.image drawInRect:CGRectMake(0, 0, width, height)]; 
    UIGraphicsPopContext(); 
    UIImage *newimage = UIGraphicsGetImageFromCurrentImageContext(); 
    UIGraphicsEndImageContext(); 

    NSUInteger i1 = [self.view.subviews indexOfObject:self.MobileImage]; 
    UIView *superview = self.MobileImage.superview; 
    [self.MobileImage removeFromSuperview]; 
    self.MobileImage.image = newimage; 
    [superview insertSubview:self.MobileImage atIndex:i1]; 
#else // the code resizes but causes image to sit on bottom of screen 
    NSLog(@"Using CGRectMake"); 
    self.MobileImage.frame = CGRectMake(0.0, 0.0, width, height); 
#if 1 // With/without next three lines, image still sits on bottom of screen 
    self.MobileImage.center = CGPointMake(width/2, height/2); 
    self.MobileImage.autoresizingMask = UIViewAutoresizingFlexibleTopMargin | UIViewAutoresizingFlexibleBottomMargin | UIViewAutoresizingFlexibleLeftMargin | UIViewAutoresizingFlexibleRightMargin; 
    self.MobileImage.autoresizesSubviews = YES; 
#endif 
#endif 
} 

預處理指令是用於測試不同的代碼。使用「#if 1」，沒有調整大小。使用「#if 0」，它會調整大小，但位於底部，無論代碼是否居中。我認爲這是一個小小的解決方案，但我已經試用和測試，比我妻子可以容忍的時間長（即忽略「待辦事項列表」），沒有任何進展，我認爲該是尋求幫助的時候了。預先感謝您的幫助。

Answer 1

要獲得新的寬度和高度，使用這樣的：

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator 
{ 
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator]; 
    CGFloat screenWidth = size.width; 
    CGFloat screenHeight = size.height; 


    UIImage* image = self.MobileImage.image; 
    CGFloat mobileImageWidth = image.size.width; 
    CGFloat mobileImageHeight = image.size.height; 

    CGFloat newMobileImageWidth = 0; 
    CGFloat newMobileImageHeight = 0; 

    double widthRatio = mobileImageWidth/screenWidth; 
    double heightRatio = mobileImageHeight/screenHeight; 

    if (widthRatio < heightRatio) { 
     newMobileImageHeight = screenHeight; 
     newMobileImageWidth = screenWidth/widthRatio; 
    } 
    else { 
     newMobileImageWidth = screenWidth; 
     newMobileImageHeight = screenHeight/heightRatio; 
    } 

    //use these new width and height for your image 

} 

Answer 2

好了，想通了，我需要的東西，使其工作。不知道這是否是最好的方式，但對我的測試程序來說已經足夠了。此外，不再需要自動調整。如果別人有同樣的問題，現在該代碼的樣子：

- (void)viewDidLoad { 
    [super viewDidLoad]; 

    CGFloat viewheight = self.view.bounds.size.height - [[UIApplication sharedApplication] statusBarFrame].size.height; 
    CGFloat width = self.view.bounds.size.width; 
    CGFloat height = width * 9/16; 
    if (height > viewheight) { // don't exceed viewable height 
     height = viewheight; 
     width = height * 16/9; 
    } 
    self.MobileImage = [[UIImageView alloc] initWithFrame:CGRectMake(0.0, 0.0, width, height)]; 
    self.MobileImage.image = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:@"sandy-ralph" ofType:@"png"]]; 
    self.MobileImage.center = self.view.center; 

    [self.view addSubview:MobileImage]; 
} 

- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator 
{ 
    [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator]; 

    CGFloat statusbarheight = [[UIApplication sharedApplication] statusBarFrame].size.height; 
    CGFloat viewheight = size.height - statusbarheight; 
    CGFloat width = size.width; 
    CGFloat height = width * 9/16; 
    if (height > viewheight) { // don't exceed viewable height 
     height = viewheight; 
     width = height * 16/9; 
    } 

    CGRect frame = self.MobileImage.frame; 
    frame.size.width = width; 
    frame.size.height = height; 
    frame.origin.x = (size.width - width)/2; 
    frame.origin.y = statusbarheight + (viewheight - height)/2; 
    self.MobileImage.frame = frame; 
}