计算NSString文本内容的高度

最新推荐文章于 2021-10-13 14:08:27 发布

原创最新推荐文章于 2021-10-13 14:08:27 发布 · 1.3k 阅读

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#NSString文本高度 #Cell高度

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本文介绍了在iOS中如何计算NSString文本内容的高度。在IOS7之前，可以使用`sizeWithFont:constrainedToSize:`方法；而在IOS7及之后，推荐使用`boundingRectWithSize:options:attributes:context:`来获取文本的高度。

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IOS7 之前的方法

- (CGSize)sizeWithFont:(UIFont *)font constrainedToSize:(CGSize)size

参数： font ：字体

size ：大小

return ： CGSize类型根据返回CGSize对象就可以得到 height

IOS 7 下方法：

- (CGRect)boundingRectWithSize:(CGSize)size

options:(NSStringDrawingOptions)

optionsattributes:(NSDictionary *)attributes

context:(NSStringDrawingContext *)context

Parameters

size

The size of the rectangle to draw in.

options

String drawing options.

attributes

A dictionary of text attributes to be applied to the string. These are the same attributes that can be applied to an NSAttributedString object, but in the case of NSString objects, the attributes apply to the entire string, rather than ranges within the string.

context

The string drawing context to use for the receiver, specifying minimum scale factor and tracking adjustments.

Return Value

The bounding rect for the receiver drawn using the given options and display characteristics. The rect origin returned from this method is the first glyph origin.

String Drawing Options

Options for customizing the way strings are drawn.

enum {
   NSStringDrawingTruncatesLastVisibleLine = 1 << 5,
   NSStringDrawingUsesLineFragmentOrigin = 1 << 0,
   NSStringDrawingUsesFontLeading = 1 << 1,
   NSStringDrawingUsesDeviceMetrics = 1 << 3,
};
typedef NSInteger NSStringDrawingOptions;

NSStringDrawingTruncatesLastVisibleLine

Truncate and add an ellipsis character to the last visible line if the text does not fit into the specified bounds. This option is ignored if theNSStringDrawingUsesLineFragmentOrigin option is not also specified.

NSStringDrawingUsesLineFragmentOrigin

The origin specified when drawing the string is the line fragment origin and not the baseline origin.

NSStringDrawingUsesFontLeading

Use the font leading information to calculate line heights.

NSStringDrawingUsesDeviceMetrics

Use the image glyph bounds (instead of the typographic bounds) when computing layout.