如何在 UITextView 中的每一行添加无序列表或项目符号

Question

所以基本上我想向UITextView 添加一个无序列表。而另一个UITextView 我想添加一个有序列表。

我尝试使用此代码，但它只在用户第一次按 Enter 后给了我一个要点（仅此而已），我什至无法退格。

- (void)textViewDidChange:(UITextView *)textView
{
    if ([myTextField.text isEqualToString:@"\n"]) {
        NSString *bullet = @"\u2022";
        myTextField.text = [myTextField.text stringByAppendingString:bullet];
    }
}

如果您只找到一种使用 Swift 执行它的方法，请随时发布 Swift 版本的代码。

Answer 1

问题是你正在使用

if ([myTextField.text isEqualToString:@"\n"]) {

作为您的条件，如果您的myTextField.text 的整体等于“\n”，则该块将执行。但是，如果您没有输入任何内容但“\n”，则整个myTextField.text 仅等于“\n”。这就是为什么现在，此代码仅在“用户第一次按下回车时”起作用；当你说“我什至不能退格”时，问题实际上是通过调用textViewDidChange: 来重新添加项目符号点，因为仍然满足相同的条件。

在这种情况下，我建议不要使用textViewDidChange:，而是使用shouldChangeTextInRange:，这样无论替换文本在UITextView 文本字符串中的位置如何，您都可以知道它是什么。通过使用这种方法，即使在文本块的中间输入换行符，您也可以自动插入项目符号点......例如，如果用户决定输入一堆信息，然后跳回几行输入更多信息，然后尝试在两者之间按换行符，以下应该仍然有效。以下是我的建议：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text {

    // If the replacement text is "\n" and the
    // text view is the one you want bullet points
    // for
    if ([text isEqualToString:@"\n"]) {

        // If the replacement text is being added to the end of the
        // text view, i.e. the new index is the length of the old
        // text view's text...
        if (range.location == textView.text.length) {
            // Simply add the newline and bullet point to the end
            NSString *updatedText = [textView.text stringByAppendingString:@"\n\u2022 "];
            [textView setText:updatedText];
        }

        // Else if the replacement text is being added in the middle of
        // the text view's text...
        else {

            // Get the replacement range of the UITextView
            UITextPosition *beginning = textView.beginningOfDocument;
            UITextPosition *start = [textView positionFromPosition:beginning offset:range.location];
            UITextPosition *end = [textView positionFromPosition:start offset:range.length];
            UITextRange *textRange = [textView textRangeFromPosition:start toPosition:end];

            // Insert that newline character *and* a bullet point
            // at the point at which the user inputted just the
            // newline character
            [textView replaceRange:textRange withText:@"\n\u2022 "];

            // Update the cursor position accordingly
            NSRange cursor = NSMakeRange(range.location + @"\n\u2022 ".length, 0);
            textView.selectedRange = cursor;

        }
        // Then return "NO, don't change the characters in range" since
        // you've just done the work already
        return NO;
    }

    // Else return yes
    return YES;
}

Answer 2

以防万一，有人正在寻找解决同一问题的 Swift 2.x 解决方案，这里有一个解决方案：

func textView(textView: UITextView, shouldChangeTextInRange range: NSRange, replacementText text: String) -> Bool {
    // If the replacement text is "\n" and the
    // text view is the one you want bullet points
    // for
    if (text == "\n") {
        // If the replacement text is being added to the end of the
        // text view, i.e. the new index is the length of the old
        // text view's text...


        if range.location == textView.text.characters.count {
            // Simply add the newline and bullet point to the end
            var updatedText: String = textView.text!.stringByAppendingString("\n \u{2022} ")
            textView.text = updatedText
        }
        else {

            // Get the replacement range of the UITextView
            var beginning: UITextPosition = textView.beginningOfDocument
            var start: UITextPosition = textView.positionFromPosition(beginning, offset: range.location)!
            var end: UITextPosition = textView.positionFromPosition(start, offset: range.length)!
            var textRange: UITextRange = textView.textRangeFromPosition(start, toPosition: end)!
            // Insert that newline character *and* a bullet point
            // at the point at which the user inputted just the
            // newline character
            textView.replaceRange(textRange, withText: "\n \u{2022} ")
            // Update the cursor position accordingly
            var cursor: NSRange = NSMakeRange(range.location + "\n \u{2022} ".length, 0)
            textView.selectedRange = cursor
        }

        return false


    }
    // Else return yes
    return true
}

Answer 3

Swift 5.x 版本。

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        //
        // If the replacement text is "\n" and the
        // text view is the one you want bullet points
        // for
        if (text == "\n") {
            // If the replacement text is being added to the end of the
            // text view, i.e. the new index is the length of the old
            // text view's text...


            if range.location == textView.text.count {
                // Simply add the newline and bullet point to the end
                let updatedText: String = textView.text! + "\n \u{2022} "
                textView.text = updatedText
            }
            else {

                // Get the replacement range of the UITextView
                let beginning: UITextPosition = textView.beginningOfDocument
                
                let start: UITextPosition = textView.position(from: beginning, offset: range.location)!
                let end: UITextPosition = textView.position(from: start, offset: range.length)!
                
                let textRange: UITextRange = textView.textRange(from: start, to: end)!
                // Insert that newline character *and* a bullet point
                // at the point at which the user inputted just the
                // newline character
                textView.replace(textRange, withText: "\n \u{2022} ")
                // Update the cursor position accordingly
                let cursor: NSRange = NSMakeRange(range.location + "\n \u{2022} ".count, 0)
                textView.selectedRange = cursor
            }

            return false


        }
        // Else return yes
        return true
    }