iphone - 如何计算 CATextLayer 字符串的边界框？

Question

乍一看我的问题看起来很简单，但似乎我真的找不到解决方案。它是这样的:我想计算 CATextLayer 字符串的边界框。这是我所做的:

CATextLayer *textLayer = [CATextLayer layer];
textLayer.frame = CGRectMake(80, 0.0f, 36.0f, 18.0f);
textLayer.string = @"12";
textLayer.fontSize = [UIFont systemFontSize];
textLayer.foregroundColor = [UIColor whiteColor].CGColor;

NSLog(@"(width,height)=(%f,%f)",
[textLayer.string sizeWithFont:textLayer.font].width,
[textLayer.string sizeWithFont:textLayer.font].height);

问题是输出总是:(width,height) = (8.000000,0.000000)

Answer 1

使用sizeWithFont:constrainedToSize:lineBreakMode:

[someString sizeWithFont:yourFont
       constrainedToSize:CGSizeMake(maxWidthYouSpecify, CGFLOAT_MAX)
           lineBreakMode:UILineBreakModeWordWrap];