关于tableview高度自适应的一个方法

最新推荐文章于 2024-07-26 20:51:40 发布

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最新推荐文章于 2024-07-26 20:51:40 发布

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分类专栏： iOS开发

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本文深入解析了在iOS7中，如何从使用sizeWithFont:constrainedToSize:lineBreakMode到采用boundingRectWithSize:options:attributes:context:方法来处理字符串绘制。详细介绍了各个参数的作用以及返回值特性，同时强调了正确绘制多行文本时需传递NSStringDrawingUsesLineFragmentOrigin作为参数的重要性。

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网上看了很多例子，都是用这个方法实现

- (CGSize)sizeWithFont:(UIFont *)font constrainedToSize:(CGSize)size lineBreakMode:(UILineBreakMode)lineBreakMode;

不过查阅apple文档发现，在iOS7中用

boundingRectWithSize：options:attributes:context:替代了。

- (CGRect)boundingRectWithSize:(CGSize)size options:(NSStringDrawingOptions)options attributes:(NSDictionary *)attributes context:(NSStringDrawingContext *)context

Parameters

参数：1 size label的大小 2 string 绘制选项 3 属性 4 上下文。返回一个给定的选项和特征值给这个矩形边界给接受者。这个矩形边界的origin值为第一个符号的origin值。下面是原文：

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.

Discussion

To correctly draw and size multi-line text, pass NSStringDrawingUsesLineFragmentOrigin in the options parameter.

This method returns fractional sizes (in the size component of the returned CGRect); to use a returned size to size views, you must use raise its value to the nearest higher integer using the ceil function.