iOS 指定高度得到可顯示文本最大字號，字符串高度、寬度計算

/// 文本字號計算 指定單行字符串高度
/// @param height 返回單行可顯示的最大字號
-(CGFloat)fontSizeFromHeight:(CGFloat)height
{
    CGFloat fontSize = 0;
    for (int i = 0; i < (int)height ; i++)
    {
        CGFloat h = [self strHeightFromWidth:0 font:[UIFont systemFontOfSize:i] str:@"高"];
        if (height - h >= 0)
        {
            fontSize = i;
        }
    }

    return fontSize;
}

/// 字符串高度計算
/// @param width 指定寬度
/// @param font 指定字體
/// @param str  指定字符串
-(CGFloat)strHeightFromWidth:(CGFloat)width font:(UIFont *)font str:(NSString *)str
{
    CGSize baseSize = CGSizeMake(width, CGFLOAT_MAX);
    if (!font)
    {
        font = [UIFont systemFontOfSize:16.0f];
    }
    CGSize labelsize  = [str boundingRectWithSize:baseSize
                                          options:NSStringDrawingUsesLineFragmentOrigin
                                       attributes:@{NSFontAttributeName:font}
                                          context:nil].size;
    return labelsize.height;
}

/// 字符串寬度計算
/// @param heigh 指定高度
/// @param font 指定字體
/// @param str 指定字符串
-(CGFloat)strWidthtFromHeigh:(CGFloat)heigh  font:(UIFont *)font str:(NSString *)str
{

    CGSize baseSize = CGSizeMake( CGFLOAT_MAX , heigh);
    if (!font)
    {
        font = [UIFont systemFontOfSize:16.0f];
    }
    CGSize labelsize  = [str boundingRectWithSize:baseSize
                                          options:NSStringDrawingUsesLineFragmentOrigin
                                       attributes:@{NSFontAttributeName:font}
                                          context:nil].size;
    return labelsize.width;
}