read handle from reg and show the window

v2rayN/v2rayN/Forms/MainForm.cs

@@ -1138,6 +1138,12 @@ namespace v2rayN.Forms
             ShowInTaskbar = false;
 
             SetVisibleCore(false);
+
+            //write Handle to reg
+            if (IsHandleCreated)
+            {
+                Utils.RegWriteValue(Global.MyRegPath, Utils.WindowHwndKey, Convert.ToString((long)Handle));
+            }
         }
 
         #endregion

v2rayN/v2rayN/Program.cs

@@ -1,18 +1,13 @@
 using System;
-using System.Diagnostics;
 using System.Threading;
 using System.Windows.Forms;
 using v2rayN.Forms;
-using v2rayN.Properties;
 using v2rayN.Tool;
 
 namespace v2rayN
 {
     static class Program
     {
-        [System.Runtime.InteropServices.DllImport("user32.dll")]
-        private static extern bool SetProcessDPIAware();
-
         /// <summary>
         /// 应用程序的主入口点。
         /// </summary>
@@ -21,7 +16,7 @@ namespace v2rayN
         {
             if (Environment.OSVersion.Version.Major >= 6)
             {
-                SetProcessDPIAware();
+                Utils.SetProcessDPIAware();
             }
 
             Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);
@@ -47,6 +42,22 @@ namespace v2rayN
             }
             else
             {
+                try
+                {
+                    //read handle from reg and show the window
+                    long.TryParse(Utils.RegReadValue(Global.MyRegPath, Utils.WindowHwndKey, ""), out long llong);
+                    if (llong > 0)
+                    {
+                        var hwnd = (IntPtr)llong;
+                        if (Utils.IsWindow(hwnd))
+                        {
+                            Utils.ShowWindow(hwnd, 4);
+                            Utils.SwitchToThisWindow(hwnd, true);
+                            return;
+                        }
+                    }
+                }
+                catch { }
                 UI.ShowWarning($"v2rayN is already running(v2rayN已经运行)");
             }
         }

v2rayN/v2rayN/Tool/Utils.cs

@@ -24,6 +24,7 @@ using System.Web;
 using log4net;
 using System.Linq;
 using System.Security.Cryptography;
+using System.Runtime.InteropServices;
 
 namespace v2rayN
 {
@@ -1111,5 +1112,30 @@ namespace v2rayN
 
         #endregion
 
+
+        #region Windows API
+
+        public static string WindowHwndKey
+        {
+            get
+            {
+                return $"WindowHwnd_{GetMD5(StartupPath())}";
+            }
+        }
+
+        [DllImport("user32.dll")]
+        public static extern bool SetProcessDPIAware();
+
+        [DllImport("user32.dll")]
+        public static extern int ShowWindow(IntPtr hwnd, int nCmdShow);
+
+        [DllImport("user32.dll")]
+        public static extern int SwitchToThisWindow(IntPtr hwnd, bool fUnknown);
+
+        [DllImport("user32.dll")]
+        public static extern bool IsWindow(IntPtr hwnd);
+
+
+        #endregion
     }
 }