捉襟见肘之UIView中contentMode属性

UIView.h

@property(nonatomic) UIViewContentMode contentMode; // default is UIViewContentModeScaleToFill

typedef NS_ENUM(NSInteger, UIViewContentMode) {
    UIViewContentModeScaleToFill,
    UIViewContentModeScaleAspectFit,      // contents scaled to fit with fixed aspect. remainder is transparent
    UIViewContentModeScaleAspectFill,     // contents scaled to fill with fixed aspect. some portion of content may be clipped.
    UIViewContentModeRedraw,              // redraw on bounds change (calls -setNeedsDisplay)
    UIViewContentModeCenter,              // contents remain same size. positioned adjusted.
    UIViewContentModeTop,
    UIViewContentModeBottom,
    UIViewContentModeLeft,
    UIViewContentModeRight,
    UIViewContentModeTopLeft,
    UIViewContentModeTopRight,
    UIViewContentModeBottomLeft,
    UIViewContentModeBottomRight,
};

找资料的时候，找到这张图片，简单粗暴，直接拿来领悟一下就可以了。

特别提到：

aspect ratio （高宽比）

clipped to fill（裁剪填充）

在整理一下她们的定义：

UIViewContentModeScaleAspectFit：
The option to scale the content to fit the size of the view by maintaining the aspect ratio. Any remaining area of the view’s bounds is transparent.
 
这个选项用来缩放当前视图大小来保持当前视图的宽高比例不变，当前视图的其他的区域是透明的