Determine if current application is activated (has focus)

Question

Note: There's a very similar question , but it's WPF-specific; this one is not.

How can I determine if the current application is activated (ie has focus)?

Answer 1

This works:

/// <summary>Returns true if the current application has focus, false otherwise</summary>
public static bool ApplicationIsActivated()
{
    var activatedHandle = GetForegroundWindow();
    if (activatedHandle == IntPtr.Zero) {
        return false;       // No window is currently activated
    }

    var procId = Process.GetCurrentProcess().Id;
    int activeProcId;
    GetWindowThreadProcessId(activatedHandle, out activeProcId);

    return activeProcId == procId;
}


[DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
private static extern IntPtr GetForegroundWindow();

[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern int GetWindowThreadProcessId(IntPtr handle, out int processId);

It has the advantage of being thread-safe, not requiring the main form (or its handle) and is not WPF or WinForms specific. It will work with child windows (even independent ones created on a separate thread). Also, there's zero setup required.

The disadvantage is that it uses a little P/Invoke, but I can live with that :-)

Answer 2

since it's likely that some element in your UI has contain focus for the form to be active try:

this.ContainsFocus

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.containsfocus(v=vs.110).aspx

Answer 3

The solution I found which requires neither native calls nor requires handling events is to check Form.ActiveForm . In my tests, that was null when no window in the application was focused and otherwise non-null.

var windowInApplicationIsFocused = Form.ActiveForm != null;

Ah, this is specific to winforms. But that applies to my situation ;-).

Answer 4

您可以订阅主窗口的已激活事件

Answer 5

In WPF the easiest way to check if a window is active is:

if(this.IsActive)
{
 //the window is active
}

Answer 6

处理主申请表格的已激活事件 。

Answer 7

First get the handle either using:

IntPtr myWindowHandle;

myWindowHandle = new WindowInteropHelper(Application.Current.MainWindow).Handle;

or

HwndSource source = (HwndSource)HwndSource.FromVisual(this);
myWindowHandle = source.Handle;

Then compare whethers it is the ForeGroundWindow:

if (myWindowHandle == GetForegroundWindow()) 
{
  // Do stuff!

}

[DllImport("user32.dll")]
private static extern IntPtr GetForegroundWindow();