An Introduction to JNI using a Bottom Up Approach: Step 1

Continued from An Introduction to JNI using a Bottom Up Approach: Prologue.

Step 1: C++ Low Level Function

1. In your working directory, add an empty file, named "PrintOpenWindows.h". This will make the functions available other C/C++ files.
   #ifndef _PRINT_OPEN_WINDOWS_H
   #define _PRINT_OPEN_WINDOWS_H
   
   #ifdef __cplusplus
           extern "C" {
   #endif
           void printOpenWindowsEntryPoint ();
   #ifdef __cplusplus
           }
   #endif
   
   #endif
2. In your working directory, add the following code, in a file named "PrintOpenWindows.cpp":
   #include "PrintOpenWindows.h"
   #include <stdlib.h>
   #include <string.h>
   #include <tchar.h>
   #include <windows.h>
   #include <iostream>
   
   using namespace std;
   
   BOOL CALLBACK FindWindowBySubstr(HWND hwnd, LPARAM substring)
   {
       const DWORD TITLE_SIZE = 1024;
       TCHAR windowTitle[TITLE_SIZE];
   
       if (GetWindowText(hwnd, windowTitle, TITLE_SIZE))
       {
           _tprintf(TEXT("%s\n"), windowTitle);
           // Uncomment to print all windows being enumerated
           if (_tcsstr(windowTitle, LPCTSTR(substring)) != NULL)
           {
               // We found the window! Stop enumerating.
               return false;
           }
       }
       return true; // Need to continue enumerating windows
   }
   
   void printOpenWindowsEntryPoint()
   {
       cout << "PRINT_OPEN_WINDOWS ENTRY START" << endl;
       const TCHAR substring[] = TEXT("Substring");
       EnumWindows(FindWindowBySubstr, (LPARAM)substring);
       cout << "PRINT_OPEN_WINDOWS ENTRY FINISH" << endl;
   }
   
   int main()
   {
       cout << "PRINT_OPEN_WINDOWS MAIN START" << endl;
       printOpenWindowsEntryPoint();
       cout << "PRINT_OPEN_WINDOWS MAIN FINISH" << endl;
   }
3. Compile the code and run "PrintOpenWindows.exe", using the following commands:
   cd /D "C:\Users\Scott\workspace\myrepo\my-app\src\main\resources\dlls"
   
   "C:\MinGW64\bin\g++.exe" -o PrintOpenWindows.exe PrintOpenWindows.cpp
   
   PrintOpenWindows.exe
   

   Code Formatted by ToGoTutor

Continued at An Introduction to JNI using a Bottom Up Approach: Step 2.

This post was reposted from http://scottizu.wordpress.com/2013/08/21/an-introduction-to-jni-using-a-bottom-up-approach-step-1/, originally written on August 21st, 2013.