好的，我真的被困在这里了：/。我有一个（自定义！）屏幕键盘，我想使用正则表达式。
我成功地创建了一个正则表达式，只允许0-9一个comma常规键盘。
当然，这不适用于我的屏幕键盘。
我有一个有效的代码片段......
但我还有一个空格键、一个退格键和 2 个用于移动插入符号的按钮。
当我使用下面的正则表达式代码并单击空格、退格或插入符号按钮时，我收到此错误：
Object reference not set to an instance of an object.
我究竟做错了什么？
// the regex code
private Control keyb = null;
private void EditProdPriceEx_GotFocus(object sender, RoutedEventArgs e)
{
string AllowedChars = "[^0-9,]";
if (Regex.IsMatch(EditProdPriceEx.Text, AllowedChars))
{
keyb = (Control)sender;
}
}
空格键：
private void KnopSpatie_Click(object sender, RoutedEventArgs e)
{
TextBox tb = keyb as TextBox;
int selStart = tb.SelectionStart; // here is where i get the error
string before = tb.Text.Substring(0, selStart);
string after = tb.Text.Substring(before.Length);
tb.Text = string.Concat(before, " ", after);
tb.SelectionStart = before.Length + 1;
}
退格键：
private void KnopWissen_Click(object sender, RoutedEventArgs e)
{
TextBox tb = keyb as TextBox;
int cursorPosition = tb.SelectionStart; // here is where i get the error
if (cursorPosition > 0)
{
tb.Text = tb.Text.Substring(0, cursorPosition -1) + tb.Text.Substring(cursorPosition);
tb.SelectionStart = cursorPosition - 1;
}
}
移动插入符号左按钮：
private void KnopLinks_Click(object sender, RoutedEventArgs e)
{
TextBox tb = keyb as TextBox;
if (tb.SelectionStart > 0) // here is where i get the error
{
int selStart = tb.SelectionStart;
string before = tb.Text.Substring(0, selStart);
string after = tb.Text.Substring(before.Length);
tb.SelectionStart = before.Length - 1;
}
}
移动插入符号右键：
private void KnopRechts_Click(object sender, RoutedEventArgs e)
{
TextBox tb = keyb as TextBox;
if (tb.SelectionStart >= 0) // here is where i get the error
{
int selStart = tb.SelectionStart;
string before = tb.Text.Substring(0, selStart);
string after = tb.Text.Substring(before.Length);
tb.SelectionStart = before.Length + 1;
}
}