怎么得到RichTextBox中的光标位置
就是 文本框 中一闪一闪的那个 竖线条
[解决办法]
请参考代码：

        Point a = new Point();
        bool idle;

        private void richTextBox1_ContentChanged(object sender, ContentChangedEventArgs e)
        {
            if (idle)
            {
                string newText = proc.ParseXAML(richTextBox1.Xaml);
                richTextBox1.Xaml = proc.ProcessText(newText);
                idle = false;
            }
        }

        private void richTextBox1_KeyDown(object sender, KeyEventArgs e)
        {
            var rect = richTextBox1.Selection.Start.GetCharacterRect(LogicalDirection.Backward);
            a = new Point(rect.X, rect.Y);
            idle = true;
        }

        private void richTextBox1_KeyUp(object sender, KeyEventArgs e)
        {
            var newPos = richTextBox1.GetPositionFromPoint(a).GetNextInsertionPosition(LogicalDirection.Forward);
            richTextBox1.Selection.Select(newPos, newPos);
        }

[解决办法]
flex 获取焦点是application.focusManager.setFocus这样，把对象改成RichTextBox就可以了