WinForm 特殊視窗效果實作（一）：漸變淡入視窗與滑動通知提示框

效果一：漸變淡入視窗

利用 Form.Opacity 屬性（0.0 完全透明 ~ 1.0 完全不透明）搭配 Timer 元件，即可實現視窗淡入動畫。

核心程式碼

public partial class FadeInForm : Form
{
    private double _opacity = 0;
    private readonly Timer _timer;

    public FadeInForm()
    {
        InitializeComponent();
        Opacity = 0; // 起始完全透明
        
        _timer = new Timer { Interval = 50 };
        _timer.Tick += Timer_Tick;
        _timer.Start();
    }

    private void Timer_Tick(object sender, EventArgs e)
    {
        if (_opacity <= 1.0)
        {
            _opacity += 0.05;
            Opacity = _opacity;
        }
        else
        {
            _timer.Stop();
            _timer.Dispose();
        }
    }
}

進階：淡出關閉

private async void FadeInForm_FormClosing(object sender, FormClosingEventArgs e)
{
    if (e.CloseReason == CloseReason.UserClosing)
    {
        e.Cancel = true; // 先取消關閉
        _timer = new Timer { Interval = 30 };
        _timer.Tick += (s, args) =>
        {
            _opacity -= 0.1;
            Opacity = _opacity;
            if (_opacity <= 0)
            {
                _timer.Stop();
                _timer.Dispose();
                FormClosing -= FadeInForm_FormClosing; // 移除事件避免遞迴
                Close(); // 真正關閉
            }
        };
        _timer.Start();
    }
}

效果二：滑動通知提示框

從螢幕右下角向上滑入，停留數秒後向下滑出消失。類似 Outlook 新郵件提醒、Windows 通知中心風格。

關鍵實作要點

• 無邊框：FormBorderStyle = None
• 不顯示在工作列：ShowInTaskbar = false
• 置頂顯示：TopMost = true
• 起始位置：螢幕工作區右下角外側（Screen.PrimaryScreen.WorkingArea）
• 動畫計算：使用 Timer 或 Task.Delay 配合 Location.Y 漸進調整

完整滑動通知類別

public class SlideNotification : Form
{
    private readonly Timer _slideTimer = new Timer();
    private readonly Timer _stayTimer = new Timer();
    private int _targetY;
    private int _direction; // 1=上滑入, -1=下滑出
    private const int Step = 10;

    public SlideNotification(string message, int stayMs = 3000)
    {
        InitializeComponent();
        lblMessage.Text = message;
        Size = new Size(300, 100);
        FormBorderStyle = FormBorderStyle.None;
        ShowInTaskbar = false;
        TopMost = true;
        StartPosition = FormStartPosition.Manual;
    }

    public void ShowNotification()
    {
        Rectangle wa = Screen.PrimaryScreen.WorkingArea;
        Location = new Point(wa.Right - Width, wa.Bottom); // 起始：畫面外右下
        _targetY = wa.Bottom - Height; // 目標：工作區右下角
        _direction = 1;
        
        _slideTimer.Interval = 15;
        _slideTimer.Tick += SlideTimer_Tick;
        _slideTimer.Start();
        Show();
    }

    private void SlideTimer_Tick(object sender, EventArgs e)
    {
        if (_direction == 1) // 滑入
        {
            Location = new Point(Location.X, Location.Y - Step);
            if (Location.Y <= _targetY)
            {
                Location = new Point(Location.X, _targetY);
                _slideTimer.Stop();
                
                // 停留階段
                _stayTimer.Interval = 3000;
                _stayTimer.Tick += (s, args) => { _stayTimer.Stop(); StartSlideOut(); };
                _stayTimer.Start();
            }
        }
        else // 滑出
        {
            Location = new Point(Location.X, Location.Y + Step);
            if (Location.Y >= Screen.PrimaryScreen.WorkingArea.Bottom)
            {
                _slideTimer.Stop();
                Close();
            }
        }
    }

    private void StartSlideOut()
    {
        _direction = -1;
        _slideTimer.Start();
    }
}

WPF 替代方案提示

若專案使用 WPF，建議改用 Storyboard + DoubleAnimation 操作 Opacity、TranslateTransform.Y，效能更好、語法更宣告式、支援 GPU 加速。