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Closing a hook that captures global input events

Introduction

Here is an example illustrating the problem. Think, I track and show the current mouse position and the last click button and position for the user. Here is the image:

alt text

To archive the capture of click events in a Windows window, this will and will be sent to the message queue about events of other programs, I create a hook using winapi, namely the user32.dll library. This is outside the JDK sandbox, so I use JNA to call my own library.

It all works fine, but it doesn't close as I expect.

My question is: how to properly close the following sample program?

Source Example

The code below is not completely written by me, but is taken from this question in the Oracle forum and partially 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(px, py) .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(); } } }); } }
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In your branch somewhere you should call

User32.PostQuitMessage(0)

to notify your own thread (hook), which you no longer need. When you do this, check in your code

while ((USER32INST.GetMessage (msg, null, 0, 0))! = 0)

sees that you no longer need a hook and completes it from the inside. I suggest you first try to close the hook with an event internal to it, for example

CWMouseHook.WM_MBUTTONDOWN

to make sure it works correctly.

In this post: While working with the JNA mouse hook example , you can see the code that will help you. Greetings.

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Source: https://habr.com/ru/post/1333306/

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