How to set focus back to form after opening up a process (Notepad)?

问题

I open up a notepad from my program using Process.Start() but the new opened notepad covers the screen. But I do want my application to maintain its focus.

I similarly (using the same Process.Start) open up MS Excel and Word but to get focus back to my form all I need to write is:

this.Focus();

But quirk with Notepad: I open notepad (and all other processes like this)

Process process = new Process();
process.StartInfo.UseShellExecute = true;
process.EnableRaisingEvents = true;
process.StartInfo.FileName = @"abc.log";
process.Start();

Now notepad takes the focus.

I tried these:

this.Activate(), this.Focus(), needless to mention

[DllImport("user32.dll", CharSet=CharSet.Auto, ExactSpelling=true)]  
public static extern IntPtr SetFocus(HandleRef hWnd);

{
   IntPtr hWnd = myProcess.Handle;
   SetFocus(new HandleRef(null, hWnd));
}

[DllImport("User32")]
private static extern int SetForegroundWindow(IntPtr hwnd);

[DllImportAttribute("User32.DLL")]
private static extern bool ShowWindow(IntPtr hWnd, int nCmdShow);
private const int SW_SHOW = 5;
private const int SW_MINIMIZE = 6;
private const int SW_RESTORE = 9;

{
    ShowWindow(Process.GetCurrentProcess().MainWindowHandle, SW_RESTORE);
    SetForegroundWindow(Process.GetCurrentProcess().MainWindowHandle);
}

Another lengthier solution got from here.

All which still keeps the focus on notepad. Why is it so difficult to merely get focus to a window, that too application's own window?

EDIT: At best I can open the notepad minimized, but it still wouldn't give the focus to the form after trying all the above codes. Notepad opens minimized, but focus will be still on notepad (something that sometimes we see in windows xp) and form will be out of focused.

回答1:

I tried almost everything on internet (so sure about it :)). At best I could get my form on top of all other forms, but without focus (going by @Hans Passant's method). Going by heavy blocks of codes all over, I somehow felt this aint gonna be easy. So I always used SetForegroundWindow() with chunks of other code. Never thought merely SetForegroundWindow() would do the trick.

This worked.

[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
static extern bool SetForegroundWindow(IntPtr hWnd);

private void button1_Click(object sender, EventArgs e)
{ 
    Process process = new Process();
    process.StartInfo.FileName = @...\abc.log";
    process.Start();

    process.WaitForInputIdle(); //this is the key!!

    SetForegroundWindow(this.Handle);
}

At times this method yields in a focus on the parent form (in cases where my desired form is a modal child form of its parent form); in such cases, just add this.Focus() to the last line..

Even this worked:

Microsoft.VisualBasic.Interaction.Shell(@"notepad.exe D:\abc.log", 
                                        Microsoft.VisualBasic.AppWinStyle.NormalNoFocus);

Solution provided by here

回答2:

I had the same problem, i eventually wound up with programmatically calling alt-tab:

[DllImport("user32.dll")]
static extern bool PostMessage(IntPtr hWnd, UInt32 Msg, int wParam, int lParam);

private void alttab()
{
     uint WM_SYSCOMMAND = 0x0112;
     int SC_PREVWINDOW = 0xF050;            

     PostMessage(Process.GetCurrentProcess().MainWindowHandle, WM_SYSCOMMAND, SC_PREVWINDOW, 0);
}

//EDIT: You should use process.MainWindowHandle instead ofcourse

回答3:

Windows prevents apps from shoving their window into the user's face, you are seeing this at work. The exact rules when an app may steal the focus are documented in the MSDN docs for AllowSetForegroundWindow().

A back-door around this restriction is the AttachThreadInput() function. This code worked well, I did take a shortcut on finding the thread ID for the thread that owns the foreground window. Good enough for Notepad, possibly not for other apps. Do beware that Raymond Chen does not approve of this kind of hack.

    private void button1_Click(object sender, EventArgs e) {
        var prc = Process.Start("notepad.exe");
        prc.WaitForInputIdle();
        int tid = GetCurrentThreadId();
        int tidTo = prc.Threads[0].Id;
        if (!AttachThreadInput(tid, tidTo, true)) throw new Win32Exception();
        this.BringToFront();
        AttachThreadInput(tid, tidTo, false);
    }

    [DllImport("user32.dll", SetLastError = true)]
    private static extern bool AttachThreadInput(int tid, int tidTo, bool attach);
    [DllImport("kernel32.dll")]
    private static extern int GetCurrentThreadId();

回答4:

Try this:

public partial class MainForm : Form
{
    private ShowForm showForm;

    public MainForm()
    {
        InitializeComponent();
    }

    private void showButton_Click(object sender, EventArgs e)
    {
        this.showForm = new ShowForm();
        this.showForm.FormClosed += showForm_FormClosed;
        this.showForm.Show(this);
    }

    private void showForm_FormClosed(object sender, FormClosedEventArgs e)
    {
        this.Focus();
    }
}

来源：https://stackoverflow.com/questions/8881038/how-to-set-focus-back-to-form-after-opening-up-a-process-notepad

标签

winforms

process

focus

windows-shell