我通过子类化UIImageView并重写setImage：方法解决了此问题。子类将首先存储其原始值以作为原点和大小，以便可以将原始设置的大小用作边界框。
我将内容模式设置为UIViewContentModeAspectFit。在setImage内部：我抓取图像的宽高比，然后调整图像视图的大小以适合与图像相同的比例。调整大小后，我调整了帧属性以将图像视图设置为与以前相同的位置，然后调用了超级setImage:。
这会导致对图像视图的帧进行调整以完全适合图像，因此，宽高比拟合工作正常，并且图像视图帧的属性在将图像视图放置在应具有相同效果的位置上起了很大的作用。
这是我使用的一些代码：
首先，我发现它在总体上很有用，它是UIView上的一个类别，它可以通过诸如左，右，上，下，宽度，高度等属性轻松在视图上设置框架属性。
UIImageView + FrameAdditions
@interface UIView (FrameAdditions)
@property CGFloat left, right, top, bottom, width, height;
@property CGPoint origin;
@end
@implementation UIView (FrameAdditions)
- (CGFloat)left {
return self.frame.origin.x;
}
- (void)setLeft:(CGFloat)left {
self.frame = CGRectMake(left, self.frame.origin.y, self.frame.size.width, self.frame.size.height);
}
- (CGFloat)right {
return self.frame.origin.x + self.frame.size.width;
}
- (void)setRight:(CGFloat)right {
self.frame = CGRectMake(right - self.frame.size.width, self.frame.origin.y, self.frame.size.width, self.frame.size.height);
}
- (CGFloat)top {
return self.frame.origin.y;
}
- (void)setTop:(CGFloat)top {
self.frame = CGRectMake(self.frame.origin.x, top, self.frame.size.width, self.frame.size.height);
}
- (CGFloat)bottom {
return self.frame.origin.y + self.frame.size.height;
}
- (void)setBottom:(CGFloat)bottom {
self.frame = CGRectMake(self.frame.origin.x, bottom - self.frame.size.height, self.frame.size.width, self.frame.size.height);
}
- (CGFloat)width {
return self.frame.size.width;
}
- (void)setWidth:(CGFloat)width {
self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y, width, self.frame.size.height);
}
- (CGFloat)height {
return self.frame.size.height;
}
- (void)setHeight:(CGFloat)height {
self.frame = CGRectMake(self.frame.origin.x, self.frame.origin.y, self.frame.size.width, height);
}
- (CGPoint)origin {
return self.frame.origin;
}
- (void)setOrigin:(CGPoint)origin {
self.frame = CGRectMake(origin.x, origin.y, self.frame.size.width, self.frame.size.height);
}
@end
这是UIImageView的子类。它尚未经过全面测试，但应该可以使您理解。可以将其扩展为设置自己的新对齐方式。
BottomCenteredImageView
@interface BottomCenteredImageView : UIImageView
@end
@interface BottomCenteredImageView() {
CGFloat originalLeft;
CGFloat originalBottom;
CGFloat originalHeight;
CGFloat originalWidth;
}
@end
@implementation BottomCenteredImageView
- (id)initWithFrame:(CGRect)frame {
self = [super initWithFrame:frame];
if(self) {
[self initialize];
}
return self;
}
- (void)awakeFromNib {
[self initialize];
}
- (void)initialize {
originalLeft = self.frame.origin.x;
originalHeight = CGRectGetHeight(self.frame);
originalWidth = CGRectGetWidth(self.frame);
originalBottom = self.frame.origin.y + originalHeight;
}
- (void)setImage:(UIImage *)image {
if(image) {
self.width = originalWidth;
self.height = originalHeight;
self.left = originalLeft;
self.bottom = originalBottom;
float myWidthToHeightRatio = originalWidth/originalHeight;
float imageWidthToHeightRatio = image.size.width/image.size.height;
if(myWidthToHeightRatio >= imageWidthToHeightRatio) {
CGFloat newWidth = self.height * imageWidthToHeightRatio;
self.width = newWidth;
self.left = originalLeft + (originalWidth - self.width)/2;
self.bottom = originalBottom;
} else {
CGFloat newHeight = self.width / imageWidthToHeightRatio;
self.height = newHeight;
self.bottom = originalBottom;
}
self.contentMode = UIViewContentModeScaleAspectFit;
[super setImage:image];
} else {
[super setImage:image];
}
}
@end