Question

我需要一个类似CTFrameGetVisibleStringRange的方法，它可以为我提供将以换行模式（即自动换行）提供的给定大小的文本。例如，我有一个很长的文本行...我有一个给定的矩形来绘制包含在其中的文本，但是无论文本在哪里被删除，我都会继续将它呈现在它停止的另一个区域。所以我需要一个方法：

NSString * text = "The lazy fox jumped over the creek";
[text drawAtPoint:CGPointMake(0, 0) forWidth:20 withFont:[UIFont fontWithName:@"Arial" size:10] lineBreakMode:UILineBreakModeWordWrap];
// now I do I know how much it drew before it stopped rendering?

有人有什么想法吗？

**已编辑：请参阅我的解决方案。

Answer 1

我遇到了类似的问题，我使用了Mike发布的解决方案。

然而，事实证明，trimToWord经常给我一些太多的单词，而不是我指定的UILabel大小。我发现如果我将while循环运算符更改为＆gt; =而不仅仅是＆gt;，它可以完美地运行。

我还添加了一些用于获取剩余字符串的ivars（chopIndex和remainingBody），以便我可以在下一个UILabel中显示它。

这是我使用的解决方案。

-(NSString*) rewindOneWord:(NSString*) str{
    // rewind by one word
    NSRange lastspace = [str rangeOfString:@" " options:NSBackwardsSearch];
    if (lastspace.location != NSNotFound){
        int amount = [str length]-lastspace.location;
        chopIndex -= amount;
        return [str substringToIndex:lastspace.location];
    }else {
        // no spaces, lets just rewind 2 characters at a time
        chopIndex -= 2;
        return [str substringToIndex:[str length]-2];
    }
}

// returns only how much text it could render with the given stipulations   
-(NSString*) trimToWord:(NSString*)str sizeConstraints:(CGSize)availableSize withFont:(UIFont*)font{
    if(str == @"")
        return str;

    CGSize measured = [str sizeWithFont:font constrainedToSize:CGSizeMake(availableSize.width, CGFLOAT_MAX) lineBreakMode:UILineBreakModeWordWrap];
    // 'guess' how much we will need to cut to save on processing time
    float choppedPercent = (((double)availableSize.height)/((double)measured.height));
    if(choppedPercent >= 1.0){
        //entire string can fit in availableSize
        remainingBody = @"";
        return str;
    }

    chopIndex = choppedPercent*((double)[str length]);
    str = [str substringToIndex:chopIndex];
    // rewind to the beginning of the word in case we are in the middle of one
    do{
        str = [self rewindOneWord:str];
        measured = [str sizeWithFont:font constrainedToSize:availableSize lineBreakMode:UILineBreakModeWordWrap];
    }while(measured.height>=availableSize.height);

    //increment past the last space in the chopIndex
    chopIndex++;

    //update the remaining string
    remainingBody = [remainingBody substringFromIndex:chopIndex];

    return str;
}

Answer 2

这是一个解决方案。它相当快。它“猜测”首先剁碎然后逐字翻滚。 sizewithFont调用是相当昂贵的，所以这个初步的“猜测”步骤很重要。主要方法是trimToWord：sizeConstraints：withFont。

随意评论我如何改善这一点。

-(NSString*) rewindOneWord:(NSString*) str{
    // rewind by one word
    NSRange lastspace = [str rangeOfString:@" " options:NSBackwardsSearch];
    if (lastspace.location != NSNotFound){
        int amount = [str length]-lastspace.location;
        return [str substringToIndex:lastspace.location];
    }else {
        // no spaces, lets just rewind 2 characters at a time
        return [str substringToIndex:[str length]-2];
    }
}

// returns only how much text it could render with the given stipulations   
-(NSString*) trimToWord:(NSString*) str sizeConstraints:(CGSize) avail withFont:(UIFont*) font{
    CGSize measured = [str sizeWithFont:font constrainedToSize:CGSizeMake(avail.width, 1000000) lineBreakMode:UILineBreakModeWordWrap];
    // 'guess' how much we will need to cut to save on processing time
    float choppedPercent = (((double)avail.height)/((double)measured.height));
    if (choppedPercent >= 1.0){
        return str;
    }

    int chopIndex = choppedPercent*((double)[str length]);
    str = [str substringToIndex:chopIndex];
    // rewind to the beginning of the word in case we are in the middle of one
    str = [self rewindOneWord:str];
    measured = [str sizeWithFont:font constrainedToSize:avail lineBreakMode:UILineBreakModeWordWrap];
    while (measured.height>avail.height){
        str = [self rewindOneWord:str];
        measured = [str sizeWithFont:font constrainedToSize:avail lineBreakMode:UILineBreakModeWordWrap];
    }
    return str;
}

Answer 3

我不认为，CTFrameGetVisibleStringRange有替代，虽然我们可以使用以下方法获得相同的结果。

- (CGSize)sizeWithFont:(UIFont *)font forWidth:(CGFloat)width lineBreakMode:(UILineBreakMode)lineBreakMode

Apple文档

http://developer.apple.com/library/ios/#documentation/uikit/reference/NSString_UIKit_Additions/Reference/Reference.html

已编辑：以下代码显示了我的方法

NSString * text = "The lazy fox jumped over the creek";

NSArray* m_Array = [text  componentsSeparatedByCharactersInSet: [NSCharacterSet characterSetWithCharactersInString:@" "]];

CGSize mySize = CGSizeMake(300,180);
NSMutableString* myString = [[NSMutableString alloc] initWithString:@""];

//The below code till the end of the while statement could be put in separate function.

CGSize tempSize = CGSizeMake(0,0);
NSInteger index = 0 ;
do
{
      [myString  appendString:[m_Array objectAtIndex:index]];
      tempSize  = [myString  sizeWithFont:myfont constrainedToSize: 
      CGSizeMake(mySize.width, CGFLOAT_MAX) lineBreakMode: UILineBreakModeWordWrap];
      index++;

}while(tempSize.height < mySize.height && index <= [m_Array count])

//Remove the string items from m_Array till the (index-1) index,

[self RemoveItems:m_Array tillIndex:(index-1)];//Plz define you own

//you have the myString which could be fitted in CGSizeMake(300,180);


//Now start with remaining Array items with the same way as we have done above.
}

CTFrameGetVisibleStringRange等效于iOS编程？

3 个答案: