How to restore a minimized window using AppActivate(ProcessID)

The documentation for AppActivate(ProcessID) states...

The AppActivate function changes the focus to the named application or window but does not affect whether it is maximized or minimized.

Unfortunately, it doesn't then advise how y开发者_C百科ou CAN un-Minimize an application from the task bar when you want it activated.

I can't find something like a SetWindowState on the Process object, so given I have a ProcessID and/or a Process object, what can be done to bring the window into a Normal or Maximized state?

I don't see any way other than interop.

[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
const UInt32 WM_SYSCOMMAND = 0x0112;
const UInt32 SC_RESTORE    = 0xF120;

if (Process.MainWindowHandle != IntPtr.Zero)
   SendMessage(Process.MainWindowHandle, WM_SYSCOMMAND, SC_RESTORE, 0);

You could use PostMessage as well, if you don't need to know when it has been restored.

For unknown reasons, it appears that the Process.MainWindowHandle value returned from a VB6 application is not the appropriate value to pass to ShowWindow in order to restore the application from a minimized state.

In the situation where the application caption is not constant, the FindWindow API call is not useful. This code below provides a function that will return the handle to a running application based on the window's caption STARTING with a specified value.

Sample usage : Identifying the IDs...

Dim hwnd As Integer
Dim iProcessID As Integer

iProcessID = Shell("SampleApp.exe", AppWinStyle.NormalFocus)
hwnd = API.GetFirstWindowhandle("Sample App")

... restoring the application...

AppActivate(iProcessID)

If API.IsMinimized(hwnd) Then
   API.ShowWindow(hwnd)
End If

... the functional routines ...

Imports System.Runtime.InteropServices

Public Class API

   Private Declare Function apiGetTopWindow Lib "user32" Alias "GetTopWindow" (ByVal hwnd As Integer) As Integer
   Private Declare Function apiGetDesktopWindow Lib "user32" Alias "GetDesktopWindow" () As Integer
   Private Declare Function apiGetWindow Lib "user32" Alias "GetWindow" (ByVal hwnd As Integer, ByVal wCmd As Integer) As Integer
   Private Declare Function apiGetWindowTextLength Lib "user32" Alias "GetWindowTextLengthA" (ByVal hwnd As Integer) As Integer
   Private Declare Function apiGetWindowText Lib "user32" Alias "GetWindowTextA" (ByVal hwnd As Integer, ByVal lpString As String, ByVal cch As Integer) As Integer
   Private Declare Function apiShowWindow Lib "user32" Alias "ShowWindow" (ByVal hwnd As IntPtr, ByVal nCmdShow As Integer) As Integer
   Private Declare Function apiIsIconic Lib "user32" Alias "IsIconic" (ByVal hwnd As IntPtr) As Boolean

   Private Const GW_HWNDNEXT As Integer = 2
   Private Const SW_NORMAL As Integer = 1

   Public Shared Function GetFirstWindowHandle(ByVal sStartingWith As String) As Integer

      Dim hwnd As Integer
      Dim sWindowName As String

      Dim iHandle As Integer = 0

      hwnd = apiGetTopWindow(apiGetDesktopWindow)

      Do While hwnd <> 0
         sWindowName = zGetWindowName(hwnd)
         If sWindowName.StartsWith(sStartingWith) Then
            iHandle = hwnd
            Exit Do
         End If
         hwnd = apiGetWindow(hwnd, GW_HWNDNEXT)
      Loop

      Return iHandle

   End Function

   Public Shared Function IsMinimized(ByVal hwnd As Integer) As Boolean

      Dim ip As New IntPtr(hwnd)

      Return apiIsIconic(ip)

   End Function

   Public Shared Sub ShowWindow(ByVal hwnd As Integer)

      Dim ip As New IntPtr(hwnd)

      apiShowWindow(ip, SW_NORMAL)

   End Sub

   Private Shared Function zGetWindowName(ByVal hWnd As Integer) As String

      Dim nBufferLength As Integer
      Dim nTextLength As Integer
      Dim sName As String

      nBufferLength = apiGetWindowTextLength(hWnd) + 4
      sName = New String(" "c, nBufferLength)

      nTextLength = apiGetWindowText(hWnd, sName, nBufferLength)
      sName = sName.Substring(0, nTextLength) 

      Return sName

   End Function

End Class

I used the SendMessage to bring my application to the front as well. The trick to making this work all the time is to minimize and then restore. This way, the app flickers, but always restores to the correct window state of normal or maximized.

SendMessage with P/Invoke

Private Function ActivateApp()
  AppActivate(System.Diagnostics.Process.GetCurrentProcess().Id)

  'Minimize Window
  SendMessage(System.Diagnostics.Process.GetCurrentProcess().MainWindowHandle, 
    WM_SYSCOMMAND, SC_MINIMIZE, CType(0, IntPtr)

  'Restore Window
  SendMessage(System.Diagnostics.Process.GetCurrentProcess().MainWindowHandle, 
    WM_SYSCOMMAND, SC_RESTORE, CType(0, IntPtr))
End Function

<DllImport("user32.dll", SetLastError:=True, CharSet:=CharSet.Auto)> _
Private Shared Function SendMessage(ByVal hWnd As IntPtr, ByVal Msg As UInteger, ByVal wParam As UInteger, ByVal lParam As IntPtr) As IntPtr
End Function

Const WM_SYSCOMMAND As UInt32 = &H112
Const SC_RESTORE As UInt32 = &HF120
Const SC_MAXIMIZE As UInt32 = &HF030
Const SC_MINIMIZE As UInt32 = &HF020

AppActivate(ProcessID)

SendKeys "{Enter}"

It means you have to press enter key to activate the minimized process

but in case the process is not minimized then the enter key will be sent to the process and affect the process.