如何在iOS 6中计算给定宽度的NSAttributedString的高度

问题描述

现在，iOS 6中提供了NSAttributedString。出于布局目的，我想知道如何在固定宽度下计算NSAttributedString所需的高度。我正在寻找的东西相当于NSString的 - （CGSize）sizeWithFont :( UIFont *）font constrainedToSize：（CGSize）size 但是对于NSAttributedString。

Now NSAttributedString is available in iOS 6. For layout purposes, I want to know how to calculate the required height of an NSAttributedString under fixed width. I'm looking for something that's equivalent to NSString's - (CGSize)sizeWithFont:(UIFont *)font constrainedToSize:(CGSize)size but for NSAttributedString.

要计算NSAttributedStrings的绘图大小，有两种方法可用：

To calculate the drawing size of NSAttributedStrings, there are two methods available:

1. - （CGSize）size 无法使用，因为它不考虑任何宽度。


2. 我试过 - （CGRect ）boundingRectWithSize：（CGSize）大小选项：（NSStringDrawingOptions）选项上下文：（NSStringDrawingContext *）context ，但不知何故它不能给我正确的高度。我觉得这个方法很麻烦。如果我运行以下代码，它会给我边界大小：572.324951,19.000000 忽略给定宽度200.它应该给我100个高度。

1. - (CGSize)size can't be used because it does not take any width into consideration.
2. I tried - (CGRect)boundingRectWithSize:(CGSize)size options:(NSStringDrawingOptions)options context:(NSStringDrawingContext *)context, but somehow it doesn't give me the correct height. I think the method is buggy. If I run the following code, it gives me bounding size: 572.324951, 19.000000 ignoring the given width of 200. It should give me something like 100 of height.

    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] init];
    NSDictionary *attributes = @{NSFontAttributeName : [UIFont fontWithName:@"HelveticaNeue" size:15], NSForegroundColorAttributeName : [UIColor blueColor]};
    [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"Attributed String\n" attributes:attributes]];
    [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"Attributed String\n" attributes:attributes]];
    [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"Attributed String\n" attributes:attributes]];
    [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"Attributed String\n" attributes:attributes]];
    [attributedString appendAttributedString:[[NSAttributedString alloc] initWithString:@"Attributed String\n" attributes:attributes]];

    CGRect frame = [attributedString boundingRectWithSize:CGSizeMake(200, 1000) options:0 context:nil];
    NSLog(@"bounding size: %f, %f", frame.size.width, frame.size.height);

Mac OS X还有其他方法，但不适用于iOS。

There are other methods available for Mac OS X, but not for iOS.

推荐答案

选项2在iOS中使用适当的参数。

Option 2 does work in iOS with the proper parameters.

NSAttributedString *attrStr = ... // your attributed string
CGFloat width = 300; // whatever your desired width is
CGRect rect = [attrStr boundingRectWithSize:CGSizeMake(width, 10000) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil];

没有选项参数的正确值你将获得错误的高度。

Without the proper values for the options parameter you will get the wrong height.

还需要 attrStr 包含字体属性。没有字体，就无法正确计算尺寸。

It is also required that attrStr contains a font attribute. Without a font, there is no way to properly calculate the size.

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