如何用RichTextBox实现Word输入一定内容自动生成新页的功能

Question

RichTextBox编辑框默认为可以无限输入，如何限定RichTextBox的的最大输入内容(居然有涉及到了字体)，最后在捕捉这个事件，在旧的RichTextBox下方再生成一个新的RichTextBoX ?

Answer 1

你好，

我们可以用handle RichTextBox的TextChanged 事件，计算文本长度，如果超出指定长度，删除即可。

因为你希望添加新的 RichTextBox，所以 Demo 中我预留了一行：

<Grid x:Name="gd">
        <Grid.RowDefinitions>
            <RowDefinition />
            <RowDefinition />
        </Grid.RowDefinitions>
        <RichTextBox TextChanged="RichTextBox_TextChanged" />
    </Grid>

后台代码：

private void RichTextBox_TextChanged(object sender, TextChangedEventArgs e)
{
            RichTextBox rtb = (RichTextBox)sender;
            TextRange textRange = new TextRange(rtb.Document.ContentStart, rtb.Document.ContentEnd);
            var text = textRange.Text.Trim();

            if (text.Length > 10) //RichTextBox Maximum Length
            {
                int gap = 0;
                while (rtb.CaretPosition.DeleteTextInRun(-1) == 0)
                {
                    rtb.CaretPosition = rtb.CaretPosition.GetPositionAtOffset(--gap);
                }

                newrtb = new RichTextBox();
                newrtb.Background = Brushes.LightBlue;
                Grid.SetRow(newrtb, 1);
                gd.Children.Add(newrtb);

                dispatcherTimer = new System.Windows.Threading.DispatcherTimer();
                dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);
                dispatcherTimer.Interval = new TimeSpan(0,0, 0, 0, 100);
                dispatcherTimer.Start();
            }
}

System.Windows.Threading.DispatcherTimer dispatcherTimer;
RichTextBox newrtb;

private void dispatcherTimer_Tick(object sender, EventArgs e)
{
            dispatcherTimer.Stop();
            Keyboard.Focus(newrtb);
}

当输入超过10个字符后，第二行会添加一个新的RichTextBox, 输入焦点也会自动转移到此控件上：

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Answer 2

非常感谢