How to determine if a screensaver is running in Java?

Question

My Application periodicly shows information on the screen. But if the screenshot is active, the application should wait until the user returns.

Is there any way to determine if the screensaver is running?

I don't need a clean solution, u just needs to work on windows xp.

Similar question, but other technology: How to determine that a screensaver is running?

Answer 1

Try using the JNA library to invoke the SystemParametersInfo system call.

The following example uses code from the win32 examples provided by JNA:

public class JNATest {

    public static void main(String[] args) {
        W32API.UINT_PTR uiAction = new W32API.UINT_PTR(User32.SPI_GETSCREENSAVERRUNNING);
        W32API.UINT_PTR uiParam = new W32API.UINT_PTR(0);
        W32API.UINT_PTR fWinIni = new W32API.UINT_PTR(0);
        PointerByReference pointer = new PointerByReference();

        User32.INSTANCE.SystemParametersInfo(uiAction, uiParam, pointer, fWinIni);

        boolean running = pointer.getPointer().getByte(0) == 1;

        System.out.println("Screen saver running: "+running);
    }
}


public interface User32 extends W32API {

    User32 INSTANCE = (User32) Native.loadLibrary("user32", User32.class, DEFAULT_OPTIONS);

    long SPI_GETSCREENSAVERRUNNING = 0x0072;

    boolean SystemParametersInfo(
        UINT_PTR uiAction,
        UINT_PTR uiParam,
        PointerByReference pvParam,
        UINT_PTR fWinIni
      );


}

Answer 2

Well, this is absolutely not clean, but it works as a dirty workaround:

I checks if 'any' screensaver (which have .SCR suffix) is running.

  private static boolean isScreensaverRunning() {
    List<String> p = WindowsUtils.listRunningProcesses();
    for (String s : p) {
      if (s.endsWith(".SCR")) {
    return true;
      }
    }
    return false;
  }

  public static List<String> listRunningProcesses() {
    List<String> processes = new ArrayList<String>();
    try {
      String line;
      Process p = Runtime.getRuntime().exec("tasklist.exe /fo csv /nh");
      BufferedReader input = new BufferedReader
      (new InputStreamReader(p.getInputStream()));
      while ((line = input.readLine()) != null) {
      if (!line.trim().equals("")) {
          // keep only the process name
          line = line.substring(1);
      processes.add(line.substring(0, line.indexOf("\"")));
      }

      }
      input.close();
    }
    catch (Exception err) {
      err.printStackTrace();
    }
    return processes;
  }

Source of listRunningProcesses: http://www.rgagnon.com/javadetails/java-0593.html