WPF程序最小化至系统托盘之后，启动第二个实例直接激活已打开程序的两种实现

首先明确一点，如果使用Hide()，Show()来实现，它内部会改变Visibility的值，当我们第二次运行激活上个实例的时候无法直接通过ShowWindow直接激活窗口（网上也有说能激活的，但是我测试的时候发现虽然能激活，但是窗口是全黑的。。。）  所以就想了另外的方法实现这个功能。

还是直接撸代码吧（如有不足之处，请各位大佬轻喷。。指正一下小弟）：

第一种：最小化的时候直接让窗口最小化，然后任务栏图标设为false。

主窗口 cs：

public partial class MainWindow : Window
    {
        /// <summary>
        /// 系统图标
        /// </summary>
        private NotifyIcon _notifyIcon = null;
        public MainWindow()
        {
            InitializeComponent();       
            InitialTray();
            WindowState = WindowState.Maximized;
            WindowStartupLocation = WindowStartupLocation.CenterOwner;
            userControl11.popNumKeyboard.IsOpen = isOpenLittleKeyboard;//小键盘是否显示
        }
        /// <summary>
        /// 初始化系统托盘图标
        /// </summary>
        private void InitialTray()
        {
            _notifyIcon = new NotifyIcon();
            _notifyIcon.BalloonTipText = "自助打印程序运行中...";//托盘气泡显示内容
            _notifyIcon.Text = "自助打印程序";
            _notifyIcon.Visible = true;//托盘按钮是否可见
            _notifyIcon.Icon = System.Drawing.Icon.ExtractAssociatedIcon(System.Windows.Forms.Application.ExecutablePath);
            _notifyIcon.ShowBalloonTip(1000);

            ToolStripMenuItem toolStripMenuItem = new ToolStripMenuItem { Text = "退出", Size = new System.Drawing.Size(107, 24) };
            toolStripMenuItem.Click += ToolStripMenuItem_Click;

            ContextMenuStrip contextMenuStrip = new ContextMenuStrip();
            contextMenuStrip.Size = new System.Drawing.Size(108, 28);
            contextMenuStrip.Items.AddRange(new System.Windows.Forms.ToolStripItem[] { toolStripMenuItem });

            _notifyIcon.ContextMenuStrip = contextMenuStrip;
            _notifyIcon.MouseClick += notifyIcon_MouseClick;
            this.StateChanged += MainWindow_StateChanged;
        }
   private void ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        #region 窗口状态改变
        /// <summary>
        /// 窗口状态改变
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void MainWindow_StateChanged(object sender, EventArgs e)
        {
            if (this.WindowState == WindowState.Minimized)
            {
                //this.Visibility = Visibility.Hidden;
                this.ShowInTaskbar = false;
                this._notifyIcon.Visible = true;
            }
        }
        #endregion
       #region 托盘图标鼠标单击事件
        /// <summary>
        /// 托盘图标鼠标单击事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void notifyIcon_MouseClick(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {

                this.ShowInTaskbar = true;
                this.WindowState = WindowState.Normal;
                this.Activate();
                //}
            }
        }
        #endregion
    }

入口cs：（两种方法通用）

static class Program
    {
        [DllImport("user32.dll")]
        public static extern IntPtr FindWindow(string lpClassName, string lpWindowName);

        [DllImport("user32.dll ", SetLastError = true)]
        static extern void SwitchToThisWindow(IntPtr hWnd, bool fAltTab);

        [DllImport("user32.dll", EntryPoint = "ShowWindow", CharSet = CharSet.Auto)]
        public static extern int ShowWindow(IntPtr hwnd, int nCmdShow);

        public static IntPtr formhwnd;
        /// <summary>
        /// 应用程序的主入口点。
        /// </summary>
        [STAThread]
        static void Main(string[] args)
        {
            string proc = Process.GetCurrentProcess().ProcessName;
            Process[] processes = Process.GetProcessesByName(proc);
            // 该程序未运行，
            if (processes.Length <= 1)
            {
                WpfSelfServiceExe.App app = new WpfSelfServiceExe.App();
                app.StartupUri = new Uri("MainWindow.xaml", System.UriKind.Relative);
                app.Run();
            }
            else
            {
                foreach (Process process in processes)
                {
                    if (process.Id != Process.GetCurrentProcess().Id)
                    {
                        if (process.MainWindowHandle.ToInt32() == 0)
                        {
                            formhwnd = FindWindow(null, "MainWindow");
                            ShowWindow(formhwnd, 3);//1代表窗体执行this.WindowState = FormWindowState.Normal;
                            SwitchToThisWindow(formhwnd, true);
                            break;
                        }
                        else
                        {
                            // 如果窗体没有隐藏，就直接切换到该窗体并带入到前台,因为窗体除了隐藏到托盘，还可以最小化
                            SwitchToThisWindow(process.MainWindowHandle, true);
                            break;
                        }
                    }
                }
            }
        }
    }

 

第二种方法：主页cs中也用ShowWindow来操作显示和隐藏界面，入口cs和上面通用！！

    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow : Window
    {
        [DllImport("user32.dll", EntryPoint = "ShowWindow", CharSet = CharSet.Auto)]
        public static extern int ShowWindow(IntPtr hwnd, int nCmdShow);
        /// <summary>
        /// 系统图标
        /// </summary>
        private NotifyIcon _notifyIcon = null;

        public MainWindow()
        {
            InitializeComponent();    
            InitialTray();
            WindowState = WindowState.Maximized;
            WindowStartupLocation = WindowStartupLocation.CenterOwner;
            userControl11.popNumKeyboard.IsOpen = isOpenLittleKeyboard;//小键盘是否显示
        }
　　　　　/// <summary>
        /// 返回按钮
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void ReturnBtn_Click(object sender, RoutedEventArgs e)
        {                        
　　　　　　　　　ShowWindow(Process.GetCurrentProcess().MainWindowHandle, 0);
        }
        /// <summary>
        /// 初始化系统托盘图标
        /// </summary>
        private void InitialTray()
        {
            _notifyIcon = new NotifyIcon();
            _notifyIcon.BalloonTipText = "自助打印程序运行中...";//托盘气泡显示内容
            _notifyIcon.Text = "自助打印程序";
            _notifyIcon.Visible = true;//托盘按钮是否可见
            _notifyIcon.Icon = System.Drawing.Icon.ExtractAssociatedIcon(System.Windows.Forms.Application.ExecutablePath);
            _notifyIcon.ShowBalloonTip(1000);

            ToolStripMenuItem toolStripMenuItem = new ToolStripMenuItem { Text = "退出", Size = new System.Drawing.Size(107, 24) };
            toolStripMenuItem.Click += ToolStripMenuItem_Click;

            ContextMenuStrip contextMenuStrip = new ContextMenuStrip();
            contextMenuStrip.Size = new System.Drawing.Size(108, 28);
            contextMenuStrip.Items.AddRange(new System.Windows.Forms.ToolStripItem[] { toolStripMenuItem });

            _notifyIcon.ContextMenuStrip = contextMenuStrip;
            _notifyIcon.MouseClick += notifyIcon_MouseClick;       
        }

        private void ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        #region 托盘图标鼠标单击事件
        /// <summary>
        /// 托盘图标鼠标单击事件
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void notifyIcon_MouseClick(object sender, System.Windows.Forms.MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                if (WindowState == WindowState.Minimized)
                {
                    WindowState = WindowState.Normal;
                }
                this.Activate();
                ShowWindow(new System.Windows.Interop.WindowInteropHelper(this).Handle, 3);
            }
        }
        #endregion
    }