如何在UITextView中找到光标的像素位置?

时间:2010-10-13 05:11:19

标签: iphone ipad ios cursor uitextview

我正在为iPad开发一个简单的写作应用程序。

我正在尝试计算UITextView中光标的像素位置。我花了几个星期来设计这个,但我还是想不出来。

在stackoverflow中,Tony编写了一个很好的算法来查找光标的像素位置。

Pixel-Position of Cursor in UITextView

我通过一些修改实现了它,它几乎可以工作,它提供了正确的光标像素位置。但是,它只适用于英文字母。

如果行尾有中文或日文字符,UITextView执行字符包装,而不是自动换行,即使中文字符之间没有空格。我认为Tony的算法在UITextView仅执行自动换行(使用英文字母)时有效。

有没有其他方法可以在UITextView找到光标的像素位置?

或者有没有办法确定某个特定字符是否跟中文字符包装或像英文一样包装?

增加:

这是我基于Tony算法的实现。我将一个UITextView放置在横向模式中,因此其宽度为1024,我使用了大小为21的自定义字体。您应该适当更改sizeOfContentWidthsizeOfContentLinesizeOfContentWidth小于实际宽度,sizeOfContentLine大于实际字体大小(行高>字体大小)。

对于凌乱的代码和评论感到抱歉!还有一些小错误,如果你在行尾输入中文字符(没有自动换行),它会给出错误的位置。

#define sizeOfContentWidth 1010
#define sizeOfContentHeight 1000
#define sizeOfContentLine 25

    // Stores the original position of the cursor
NSRange originalPosition = textView.selectedRange;    

// Computes textView's origin
CGPoint origin = textView.frame.origin;

// Checks whether a character right to the current cursor is a non-space character
unichar c = ' ';

if(textView.selectedRange.location != [textView.text length])
    c = [textView.text characterAtIndex:textView.selectedRange.location];

// If it's a non-space or newline character, then the current cursor moves to the end of that word
if(c != 32 && c != 10){
    NSRange delimiter = [textView.text rangeOfCharacterFromSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]
                                                       options:NSLiteralSearch
                                                         range:NSMakeRange(textView.selectedRange.location, [textView.text length] - textView.selectedRange.location)];

    if(delimiter.location == NSNotFound){
        delimiter.location = [textView.text length];
    }

    textView.selectedRange = delimiter;
}

// Deviation between the original cursor location and moved location
int deviationLocation = textView.selectedRange .location - originalPosition.location;

// Substrings the part before the cursor position
NSString* head = [textView.text substringToIndex:textView.selectedRange.location];

// Gets the size of this part
CGSize initialSize = [head sizeWithFont:textView.font constrainedToSize:CGSizeMake(sizeOfContentWidth, sizeOfContentHeight)];

// Gets the length of the head
NSUInteger startOfLine = [head length];

// The first line
BOOL isFirstLine = NO;

if(initialSize.height / sizeOfContentLine == 1){
    isFirstLine = YES;
}

while (startOfLine > 0 && isFirstLine == NO) {
    // 1. Adjusts startOfLine to the beginning of the first word before startOfLine
    NSRange delimiter = [head rangeOfCharacterFromSet:[NSCharacterSet whitespaceAndNewlineCharacterSet] options:NSBackwardsSearch range:NSMakeRange(0, startOfLine)];

    // Updates startsOfLine
    startOfLine = delimiter.location;

    // 2. Check if drawing the substring of head up to startOfLine causes a reduction in height compared to initialSize. 
    NSString *tempHead = [head substringToIndex:startOfLine];

    // Gets the size of this temp head
    CGSize tempHeadSize = [tempHead sizeWithFont:textView.font constrainedToSize:CGSizeMake(sizeOfContentWidth, sizeOfContentHeight)];

    // Counts the line of the original
    int beforeLine = initialSize.height / sizeOfContentLine;

    // Counts the line of the one after processing
    int afterLine = tempHeadSize.height / sizeOfContentLine;

    // 3. If so, then you've identified the start of the line containing the cursor, otherwise keep going.
    if(beforeLine != afterLine)
        break;
}

// Substrings the part after the cursor position
NSString* tail;

if(isFirstLine == NO)
    tail = [head substringFromIndex:(startOfLine + deviationLocation)];
else {
    tail = [head substringToIndex:(startOfLine - deviationLocation)];
}

// Gets the size of this part
CGSize lineSize = [tail sizeWithFont:textView.font forWidth:sizeOfContentWidth lineBreakMode:UILineBreakModeWordWrap];

// Gets the cursor position in coordinate
CGPoint cursor = origin;    
cursor.x += lineSize.width;
cursor.y += initialSize.height - lineSize.height;

// Back to the original position
textView.selectedRange = originalPosition;

// Debug
printf("x: %f,   y: %f\n", cursor.x, cursor.y);

2 个答案:

答案 0 :(得分:2)

如果您只针对IOS7,则可以使用 UITextView方法:

- (CGRect)caretRectForPosition:(UITextPosition *)position;

简短样本:

NSRange range; // target location in text that you should get from somewhere, e.g. textview.selectedRange
UITextView textview; // the text view

UITextPosition *start = [textview positionFromPosition:textview.beginningOfDocument offset:range.location];
CGRect caretRect = [self caretRectForPosition:start]; // caret rect in UITextView

答案 1 :(得分:0)

这可能是相当低效的,但是你可以采用你发布的代码的相同基本原理并获取光标所在的文本行,并循环遍历每个单独的字符并执行[NSString sizeWithFont:forWidth:lineBreakMode:]来计算每个字符角色的宽度,你可以为你的x位置添加所有这些吗?只是一个想法,但可能有助于通过自动换行解决问题。