JNA - How to call System-functions? (rotate, screen off) [closed]

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Closed 5 years ago.

I am completely new to the JNA interface (? library?) - but I see some of the System-functions are only accessible in Java via JNA. I wanna do some display-stuff, namely rotating and turn-off-monitor. For both function I have to call some system-functions - for the turn-off-monitor I found the link as well as for the rotate the link. But to be honest, I have no real clue how to start with one of them.

Could somebody give an idea how to start resp. how to implement?

回答1:

OK, I had to try the monitor on and off bit, and it worked! Too cool!

import com.sun.jna.Native;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.platform.win32.WinDef.LPARAM;
import com.sun.jna.platform.win32.WinDef.LRESULT;
import com.sun.jna.platform.win32.WinDef.WPARAM;
import com.sun.jna.platform.win32.WinUser;
import com.sun.jna.win32.StdCallLibrary;

public class TurnOffMonitor {
   public interface User32 extends StdCallLibrary {
      User32 INSTANCE = (User32) Native.loadLibrary("user32", User32.class);
      int SC_MONITORPOWER = 0xF170;
      int SC_MONITOR_OFF = 2;
      int SC_MONITOR_ON = -1;

      LRESULT SendMessageA(HWND paramHWND, int paramInt, WPARAM paramWPARAM,
            LPARAM paramLPARAM);

      LRESULT SendMessageA(HWND paramHWND, int paramInt, int paramInt2,
            LPARAM paramLPARAM);
   }

   private static final long SLEEP_TIME = 4 * 1000; // 4 seconds

   public static void main(String[] args) {
      final User32 user32 = User32.INSTANCE;
      System.out.println("Foo");

      user32.SendMessageA(WinUser.HWND_BROADCAST, WinUser.WM_SYSCOMMAND,
            User32.SC_MONITORPOWER, new LPARAM(User32.SC_MONITOR_OFF));

      try {
         Thread.sleep(SLEEP_TIME);
      } catch (InterruptedException e) {}

      user32.SendMessageA(WinUser.HWND_BROADCAST, WinUser.WM_SYSCOMMAND,
            User32.SC_MONITORPOWER, new LPARAM(User32.SC_MONITOR_ON));

   }
}

来源：https://stackoverflow.com/questions/20775652/jna-how-to-call-system-functions-rotate-screen-off