Closing a hook that captures global input events
- by Margus
Intro
Here is an example to illustrate the problem. Consider I am tracking and displaying mouse global current position and last click button and position to the user. Here is an image:
To archive capturing click events on windows box, that would and will be sent to the other programs event messaging queue, I create a hook using winapi namely user32.dll library. This is outside JDK sandbox, so I use JNA to call the native library.
This all works perfectly, but it does not close as I expect it to.
My question is - How do I properly close following example program?
Example source
Code below is not fully written by Me, but taken from this question in Oracle forum and partly fixed.
import java.awt.AWTException;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.GridLayout;
import java.awt.MouseInfo;
import java.awt.Point;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.JFrame;
import javax.swing.JLabel;
import com.sun.jna.Native;
import com.sun.jna.NativeLong;
import com.sun.jna.Platform;
import com.sun.jna.Structure;
import com.sun.jna.platform.win32.BaseTSD.ULONG_PTR;
import com.sun.jna.platform.win32.Kernel32;
import com.sun.jna.platform.win32.User32;
import com.sun.jna.platform.win32.WinDef.HWND;
import com.sun.jna.platform.win32.WinDef.LRESULT;
import com.sun.jna.platform.win32.WinDef.WPARAM;
import com.sun.jna.platform.win32.WinUser.HHOOK;
import com.sun.jna.platform.win32.WinUser.HOOKPROC;
import com.sun.jna.platform.win32.WinUser.MSG;
import com.sun.jna.platform.win32.WinUser.POINT;
public class MouseExample {
final JFrame jf;
final JLabel jl1, jl2;
final CWMouseHook mh;
final Ticker jt;
public class Ticker extends Thread {
public boolean update = true;
public void done() {
update = false;
}
public void run() {
try {
Point p, l = MouseInfo.getPointerInfo().getLocation();
int i = 0;
while (update == true) {
try {
p = MouseInfo.getPointerInfo().getLocation();
if (!p.equals(l)) {
l = p;
jl1.setText(new GlobalMouseClick(p.x, p.y)
.toString());
}
Thread.sleep(35);
} catch (InterruptedException e) {
e.printStackTrace();
return;
}
}
} catch (Exception e) {
update = false;
}
}
}
public MouseExample() throws AWTException, UnsupportedOperationException {
this.jl1 = new JLabel("{}");
this.jl2 = new JLabel("{}");
this.jf = new JFrame();
this.jt = new Ticker();
this.jt.start();
this.mh = new CWMouseHook() {
@Override
public void globalClickEvent(GlobalMouseClick m) {
jl2.setText(m.toString());
}
};
mh.setMouseHook();
jf.setLayout(new GridLayout(2, 2));
jf.add(new JLabel("Position"));
jf.add(jl1);
jf.add(new JLabel("Last click"));
jf.add(jl2);
jf.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent we) {
mh.dispose();
jt.done();
jf.dispose();
}
});
jf.setLocation(new Point(0, 0));
jf.setPreferredSize(new Dimension(200, 90));
jf.pack();
jf.setVisible(true);
}
public static class GlobalMouseClick {
private char c;
private int x, y;
public GlobalMouseClick(char c, int x, int y) {
super();
this.c = c;
this.x = x;
this.y = y;
}
public GlobalMouseClick(int x, int y) {
super();
this.x = x;
this.y = y;
}
public char getC() {
return c;
}
public void setC(char c) {
this.c = c;
}
public int getX() {
return x;
}
public void setX(int x) {
this.x = x;
}
public int getY() {
return y;
}
public void setY(int y) {
this.y = y;
}
@Override
public String toString() {
return (c != 0 ? c : "") + " [" + x + "," + y + "]";
}
}
public static class CWMouseHook {
public User32 USER32INST;
public CWMouseHook() throws UnsupportedOperationException {
if (!Platform.isWindows()) {
throw new UnsupportedOperationException(
"Not supported on this platform.");
}
USER32INST = User32.INSTANCE;
mouseHook = hookTheMouse();
Native.setProtected(true);
}
private static LowLevelMouseProc mouseHook;
private HHOOK hhk;
private boolean isHooked = false;
public static final int WM_LBUTTONDOWN = 513;
public static final int WM_LBUTTONUP = 514;
public static final int WM_RBUTTONDOWN = 516;
public static final int WM_RBUTTONUP = 517;
public static final int WM_MBUTTONDOWN = 519;
public static final int WM_MBUTTONUP = 520;
public void dispose() {
unsetMouseHook();
mousehook_thread = null;
mouseHook = null;
hhk = null;
USER32INST = null;
}
public void unsetMouseHook() {
isHooked = false;
USER32INST.UnhookWindowsHookEx(hhk);
System.out.println("Mouse hook is unset.");
}
public boolean isIsHooked() {
return isHooked;
}
public void globalClickEvent(GlobalMouseClick m) {
System.out.println(m);
}
private Thread mousehook_thread;
public void setMouseHook() {
mousehook_thread = new Thread(new Runnable() {
@Override
public void run() {
try {
if (!isHooked) {
hhk = USER32INST.SetWindowsHookEx(14, mouseHook,
Kernel32.INSTANCE.GetModuleHandle(null), 0);
isHooked = true;
System.out
.println("Mouse hook is set. Click anywhere.");
// message dispatch loop (message pump)
MSG msg = new MSG();
while ((USER32INST.GetMessage(msg, null, 0, 0)) != 0) {
USER32INST.TranslateMessage(msg);
USER32INST.DispatchMessage(msg);
if (!isHooked)
break;
}
} else
System.out
.println("The Hook is already installed.");
} catch (Exception e) {
System.err.println("Caught exception in MouseHook!");
}
}
});
mousehook_thread.start();
}
private interface LowLevelMouseProc extends HOOKPROC {
LRESULT callback(int nCode, WPARAM wParam, MOUSEHOOKSTRUCT lParam);
}
private LowLevelMouseProc hookTheMouse() {
return new LowLevelMouseProc() {
@Override
public LRESULT callback(int nCode, WPARAM wParam,
MOUSEHOOKSTRUCT info) {
if (nCode >= 0) {
switch (wParam.intValue()) {
case CWMouseHook.WM_LBUTTONDOWN:
globalClickEvent(new GlobalMouseClick('L',
info.pt.x, info.pt.y));
break;
case CWMouseHook.WM_RBUTTONDOWN:
globalClickEvent(new GlobalMouseClick('R',
info.pt.x, info.pt.y));
break;
case CWMouseHook.WM_MBUTTONDOWN:
globalClickEvent(new GlobalMouseClick('M',
info.pt.x, info.pt.y));
break;
default:
break;
}
}
return USER32INST.CallNextHookEx(hhk, nCode, wParam,
info.getPointer());
}
};
}
public class Point extends Structure {
public class ByReference extends Point implements
Structure.ByReference {
};
public NativeLong x;
public NativeLong y;
}
public static class MOUSEHOOKSTRUCT extends Structure {
public static class ByReference extends MOUSEHOOKSTRUCT implements
Structure.ByReference {
};
public POINT pt;
public HWND hwnd;
public int wHitTestCode;
public ULONG_PTR dwExtraInfo;
}
}
public static void main(String[] args) {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
new MouseExample();
} catch (AWTException e) {
e.printStackTrace();
}
}
});
}
}
