在 RichTextBox 中设置字体属性

Question

你好， 我正在 WPF 中使用 RichTextBox 开发一个编辑器，我必须实现这样的功能：如果选择了某些文本，用户可以设置所选 Text 的字体，如果没有选择任何内容，则字体应该为新文本设置。 如果我在以后的情况下设置 RTB 的字体属性（如 FontStyle、FontSize），它将设置整个文本的属性，我如何为新文本设置字体属性（即，如果用户输入文本，它将带有新的字体设置）。

Answer 1

我已经实现了一个可以更改字体大小、系列、颜色等的工具栏。我发现 wpf richtextbox 的细节可能很棘手。设置选择字体有一定意义，但是，还需要处理文本框的默认字体属性和当前插入符号属性。这是我写的内容，让它适用于大多数情况下的字体大小。 fontfamily 和 fontcolor 的过程应该相同。希望有帮助。

    public static void SetFontSize(RichTextBox target, double value)
    {
        // Make sure we have a richtextbox.
        if (target == null)
            return;

        // Make sure we have a selection. Should have one even if there is no text selected.
        if (target.Selection != null)
        {
            // Check whether there is text selected or just sitting at cursor
            if (target.Selection.IsEmpty)
            {
                // Check to see if we are at the start of the textbox and nothing has been added yet
                if (target.Selection.Start.Paragraph == null)
                {
                    // Add a new paragraph object to the richtextbox with the fontsize
                    Paragraph p = new Paragraph();
                    p.FontSize = value;
                    target.Document.Blocks.Add(p);
                }
                else
                {
                    // Get current position of cursor
                    TextPointer curCaret = target.CaretPosition;
                    // Get the current block object that the cursor is in
                    Block curBlock = target.Document.Blocks.Where
                        (x => x.ContentStart.CompareTo(curCaret) == -1 && x.ContentEnd.CompareTo(curCaret) == 1).FirstOrDefault();
                    if (curBlock != null)
                    {
                        Paragraph curParagraph = curBlock as Paragraph;
                        // Create a new run object with the fontsize, and add it to the current block
                        Run newRun = new Run();
                        newRun.FontSize = value;
                        curParagraph.Inlines.Add(newRun);
                        // Reset the cursor into the new block. 
                        // If we don't do this, the font size will default again when you start typing.
                        target.CaretPosition = newRun.ElementStart;
                    }
                }
            }
            else // There is selected text, so change the fontsize of the selection
            {
                TextRange selectionTextRange = new TextRange(target.Selection.Start, target.Selection.End);
                selectionTextRange.ApplyPropertyValue(TextElement.FontSizeProperty, value);
            }
        }
        // Reset the focus onto the richtextbox after selecting the font in a toolbar etc
        target.Focus();
    }