C#实现Winform小数字键盘模拟器

/// <summary>
/// 可接受的最小值，最小为-3.402823E+38
/// </summary>
[Browsable(true)]
[Category("Zhongzhou")]
[DefaultValue(0)]
[Description("可接受的最小值，最小为-3.402823E+38")]
public float Min { get; set; } = 0;
 
/// <summary>
/// 可接受的最大值，最大为3.402823E+38
/// </summary>
[Browsable(true)]
[Category("Zhongzhou")]
[DefaultValue(0)]
[Description("可接受的最大值，最大为3.402823E+38")]
public float Max { get; set; } = 0;
 
/// <summary>
/// 设置小数点的精度位数，默认为2位小数点
/// </summary>
[Browsable(true)]
[Category("Zhongzhou")]
[DefaultValue(2)]
[Description("设置小数点的精度位数，默认为2位小数点")]
public int Precision { get; set; } = 2;

/// <summary>
/// 当使用实物键盘输入文本内容时触发
/// </summary>
/// <param name="e"></param>
private void OnKeyPressed(KeyPressEventArgs e)
{
    //13表示回车
    if (e.KeyChar == 13)
    {
        this.OnEntered();
        e.Handled = true;
        return;
    }
    //48代表0，57代表9，8代表空格，46代表小数点
    if ((e.KeyChar < 48 || e.KeyChar >= 57) && (e.KeyChar != 8) && (e.KeyChar != 46))
    {
        e.Handled = true;
        return;
    }
 
    //判断多次输入小数点，仅允许出现1次小数点
    if (e.KeyChar == 46)
    {
        this.PointHandle();
        this.SetContentFocus();
        e.Handled = true;
        return;
    }
}
 
/// <summary>
/// 处理小数点
/// </summary>
/// <returns><see langword="true"/>表示处理成功，<see langword="false"/>表示未处理</returns>
private bool PointHandle()
{
    string content = this.ContentTextBox.Text;
    if (content.IndexOf('.') != -1)
    {
        return false;
    }
 
    if (string.IsNullOrEmpty(content))
    {
        this.SetContent("0.");
        return true;
    }
 
    //取光标位置
    int index = this.ContentTextBox.SelectionStart;
    string str = this.ContentTextBox.Text.Substring(0, index);
    if (str == "+" || str == "-")
    {
        return this.SetContent(string.Join(string.Empty, str, "0.", this.ContentTextBox.Text.Substring(index, this.ContentTextBox.Text.Length - index)));
    }
 
    return this.SetContent(string.Join(string.Empty, str, ".", this.ContentTextBox.Text.Substring(index, this.ContentTextBox.Text.Length - index)));
}

/// <summary>
/// 设置新值
/// </summary>
/// <param name="newContent">表示新值</param>
private bool SetContent(string newContent)
{
    int precision = this.Precision;
 
    if (string.IsNullOrEmpty(newContent))
    {
        this.ContentTextBox.Text = string.Empty;
        return true;
    }
 
    var scheme = newContent.Split('.');
    if (scheme.Length == 2)
    {
        var realPrecision = scheme[1].Length;
        if (realPrecision > precision)
        {
            return false;
        }
    }
 
    this.ContentTextBox.Text = newContent;
    return true;
}

 
/// <summary>
/// 清除内容
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void ClearButton_Click(object sender, EventArgs e)
{
    this.SetContent(string.Empty);
    this.SetContentFocus();
}
 
/// <summary>
/// 退格内容
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
private void BackButton_Click(object sender, EventArgs e)
{
    //取光标位置
    int index = this.ContentTextBox.SelectionStart;
    //剪切内容
    string cutStr = this.ContentTextBox.Text.Substring(0, index);
    //剩余内容
    string remainStr = this.ContentTextBox.Text.Substring(index, this.ContentTextBox.Text.Length - index);
    int position = this.SetContent(string.Join(string.Empty, cutStr.Substring(0, cutStr.Length - 1), remainStr)) ? index - 1 : index;
    this.SetContentFocus(position);
}

/// <summary>
/// 当按下回车按钮时的事件委托
/// </summary>
/// <param name="sender"></param>
/// <param name="e"></param>
public delegate void EnteredEventHandler(object sender, float e);
 
/// <summary>
/// 当按下回车按钮时的事件
/// </summary>
public event EnteredEventHandler Entered;
 
/// <summary>
/// 当迷你小键盘按下回车时触发事件
/// </summary>
protected virtual void OnEntered()
{
    float min = this.Min;
    float max = this.Max;
    var value = string.IsNullOrEmpty(this.ContentTextBox.Text) ? 0 : Convert.ToSingle(this.ContentTextBox.Text);
    if (max != 0 && value > max)
    {
        MessageBox.Show("值不在最大范围内", "提示");
        return;
    }
    if (min != 0 && value < min)
    {
        MessageBox.Show("值不在最小范围内", "提示");
        return;
    }
 
    this.Entered?.Invoke(this, value);
}
 
/// <inheritdoc cref="OnEntered"/>
private void EnterButton_Click(object sender, EventArgs e)
{
    this.OnEntered();
    this.SetContentFocus();
}