首先用C语言的GTK生成动态链接库，然后利用java的native方法调用该动态链接库就可以了，是不是很简单。
环境：
JDK 8；
OS：CentOS5；
GTK：gtk+-2.0
首先看下我的文件树（编译运行后的）：
.├── 37_drawingPic3.c├── config.sh├── Demo_03_JButton_JPanel.java├── Demo$1.class├── Demo$2.class├── Demo.class├── Demo.h└── libGTK.so
首先编写含有native方法的java程序：
import java.awt.Dimension;import java.awt.Toolkit;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.awt.GridLayout;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JPanel;class Demo extends JFrame {private Toolkit toolkit;public native void gtk_draw();Demo() {setTitle("Demo");setSize(300, 200);toolkit = getToolkit();Dimension size = toolkit.getScreenSize();System.loadLibrary("GTK");setLocation((size.width/2 - getWidth())/2, (size.height - getHeight())/2);setDefaultCloseOperation(EXIT_ON_CLOSE);JPanel panel = new JPanel();//getContentPane().add(panel);add(panel);//panel.setLayout(new GridLayout(2,2));panel.setLayout(null);JButton beep = new JButton("Beep");beep.setBounds(150, 60, 80, 30);beep.addActionListener(new ActionListener() {public void actionPerformed(ActionEvent event) {toolkit.beep();System.out.println("Beep");gtk_draw();}});JButton close = new JButton("Close");close.setBounds(50, 60, 80, 30);close.addActionListener(new ActionListener() {public void actionPerformed(ActionEvent event) {System.exit(0);}});panel.add(beep);panel.add(close);}public static void main(String[] args) {Demo demo = new Demo();demo.setVisible(true);}}
编译该java程序：
$ javac Demo_03_JButton_JPanel.java
生成Demo.class文件，改文件名是由含有native方法的类名决定。然后用javah -jni编译生成头文件：
$ javah -jni Demo
然后生成Demo.h文件，改文件名也是由含有native方法的类名决定，文件内容如下：
/* DO NOT EDIT THIS FILE - it is machine generated */#include <jni.h>/* Header for class Demo */#ifndef _Included_Demo#define _Included_Demo#ifdef __cplusplusextern "C" {#endif#undef Demo_FOCUS_TRAVERSABLE_UNKNOWN#define Demo_FOCUS_TRAVERSABLE_UNKNOWN 0L#undef Demo_FOCUS_TRAVERSABLE_DEFAULT#define Demo_FOCUS_TRAVERSABLE_DEFAULT 1L#undef Demo_FOCUS_TRAVERSABLE_SET#define Demo_FOCUS_TRAVERSABLE_SET 2L#undef Demo_TOP_ALIGNMENT#define Demo_TOP_ALIGNMENT 0.0f#undef Demo_CENTER_ALIGNMENT#define Demo_CENTER_ALIGNMENT 0.5f#undef Demo_BOTTOM_ALIGNMENT#define Demo_BOTTOM_ALIGNMENT 1.0f#undef Demo_LEFT_ALIGNMENT#define Demo_LEFT_ALIGNMENT 0.0f#undef Demo_RIGHT_ALIGNMENT#define Demo_RIGHT_ALIGNMENT 1.0f#undef Demo_serialVersionUID#define Demo_serialVersionUID -7644114512714619750LL#undef Demo_serialVersionUID#define Demo_serialVersionUID 4613797578919906343LL#undef Demo_INCLUDE_SELF#define Demo_INCLUDE_SELF 1L#undef Demo_SEARCH_HEAVYWEIGHTS#define Demo_SEARCH_HEAVYWEIGHTS 1L#undef Demo_OPENED#define Demo_OPENED 1L#undef Demo_serialVersionUID#define Demo_serialVersionUID 4497834738069338734LL#undef Demo_DEFAULT_CURSOR#define Demo_DEFAULT_CURSOR 0L#undef Demo_CROSSHAIR_CURSOR#define Demo_CROSSHAIR_CURSOR 1L#undef Demo_TEXT_CURSOR#define Demo_TEXT_CURSOR 2L#undef Demo_WAIT_CURSOR#define Demo_WAIT_CURSOR 3L#undef Demo_SW_RESIZE_CURSOR#define Demo_SW_RESIZE_CURSOR 4L#undef Demo_SE_RESIZE_CURSOR#define Demo_SE_RESIZE_CURSOR 5L#undef Demo_NW_RESIZE_CURSOR#define Demo_NW_RESIZE_CURSOR 6L#undef Demo_NE_RESIZE_CURSOR#define Demo_NE_RESIZE_CURSOR 7L#undef Demo_N_RESIZE_CURSOR#define Demo_N_RESIZE_CURSOR 8L#undef Demo_S_RESIZE_CURSOR#define Demo_S_RESIZE_CURSOR 9L#undef Demo_W_RESIZE_CURSOR#define Demo_W_RESIZE_CURSOR 10L#undef Demo_E_RESIZE_CURSOR#define Demo_E_RESIZE_CURSOR 11L#undef Demo_HAND_CURSOR#define Demo_HAND_CURSOR 12L#undef Demo_MOVE_CURSOR#define Demo_MOVE_CURSOR 13L#undef Demo_NORMAL#define Demo_NORMAL 0L#undef Demo_ICONIFIED#define Demo_ICONIFIED 1L#undef Demo_MAXIMIZED_HORIZ#define Demo_MAXIMIZED_HORIZ 2L#undef Demo_MAXIMIZED_VERT#define Demo_MAXIMIZED_VERT 4L#undef Demo_MAXIMIZED_BOTH#define Demo_MAXIMIZED_BOTH 6L#undef Demo_serialVersionUID#define Demo_serialVersionUID 2673458971256075116LL#undef Demo_EXIT_ON_CLOSE#define Demo_EXIT_ON_CLOSE 3L/** Class:Demo* Method: gtk_draw* Signature: ()V*/JNIEXPORT void JNICALL Java_Demo_gtk_1draw(JNIEnv *, jobject);#ifdef __cplusplus}#endif#endif
然后按照该头文件中的函数名编写C语言代码，并包含该头文件：
/* GTK - The GIMP Toolkit* Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald** This library is free software; you can redistribute it and/or* modify it under the terms of the GNU Lesser General Public* License as published by the Free Software Foundation; either* version 2 of the License, or (at your option) any later version.** This library is distributed in the hope that it will be useful,* but WITHOUT ANY WARRANTY; without even the implied warranty of* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU* Lesser General Public License for more details.** You should have received a copy of the GNU Lesser General Public* License along with this library; if not, write to the* Free Software Foundation, Inc., 59 Temple Place - Suite 330,* Boston, MA 02111-1307, USA.*//** Modified by the GTK+ Team and others 1997-2000. See the AUTHORS* file for a list of people on the GTK+ Team. See the ChangeLog* files for a list of changes. These files are distributed with* GTK+ at ftp:///pub/gtk/. *///#include <config.h>#include <stdio.h>#include "gtk/gtk.h"#include "Demo.h"/* Backing pixmap for drawing area */static GdkPixmap *pixmap = NULL;/* Information about cursor */static gint cursor_proximity = TRUE;static gdouble cursor_x;static gdouble cursor_y;/* Unique ID of current device */static GdkDevice *current_device;/* Erase the old cursor, and/or draw a new one, if necessary */static voidupdate_cursor (GtkWidget *widget, gdouble x, gdouble y){static gint cursor_present = 0;gint state = !current_device->has_cursor && cursor_proximity;if (pixmap != NULL){if (cursor_present && (cursor_present != state ||x != cursor_x || y != cursor_y)){gdk_draw_drawable (widget->window,widget->style->fg_gc[GTK_WIDGET_STATE (widget)],pixmap,cursor_x - 5, cursor_y - 5,cursor_x - 5, cursor_y - 5,10, 10);}cursor_present = state;cursor_x = x;cursor_y = y;if (cursor_present){gdk_draw_rectangle (widget->window,widget->style->black_gc,TRUE,cursor_x - 5, cursor_y -5,10, 10);}}}/* Create a new backing pixmap of the appropriate size */static gintconfigure_event (GtkWidget *widget, GdkEventConfigure *event){if (pixmap)g_object_unref (pixmap);pixmap = gdk_pixmap_new(widget->window,widget->allocation.width,widget->allocation.height,-1);gdk_draw_rectangle (pixmap,widget->style->white_gc,TRUE,0, 0,widget->allocation.width,widget->allocation.height);return TRUE;}/* Refill the screen from the backing pixmap */static gintexpose_event (GtkWidget *widget, GdkEventExpose *event){gdk_draw_drawable (widget->window,widget->style->fg_gc[GTK_WIDGET_STATE (widget)],pixmap,event->area.x, event->area.y,event->area.x, event->area.y,event->area.width, event->area.height);return FALSE;}/* Draw a rectangle on the screen, size depending on pressure,and color on the type of device */static voiddraw_brush (GtkWidget *widget, GdkInputSource source,gdouble x, gdouble y, gdouble pressure){GdkGC *gc;GdkRectangle update_rect;switch (source){case GDK_SOURCE_MOUSE:gc = widget->style->dark_gc[GTK_WIDGET_STATE (widget)];break;case GDK_SOURCE_PEN:gc = widget->style->black_gc;break;case GDK_SOURCE_ERASER:gc = widget->style->white_gc;break;default:gc = widget->style->light_gc[GTK_WIDGET_STATE (widget)];}update_rect.x = x - 10 * pressure;update_rect.y = y - 10 * pressure;update_rect.width = 20 * pressure;update_rect.height = 20 * pressure;gdk_draw_rectangle (pixmap, gc, TRUE,update_rect.x, update_rect.y,update_rect.width, update_rect.height);gtk_widget_queue_draw_area (widget,update_rect.x, update_rect.y,update_rect.width, update_rect.height);gdk_window_process_updates (widget->window, TRUE);}static guint32 motion_time;static voidprint_axes (GdkDevice *device, gdouble *axes){int i;if (axes){g_print ("%s ", device->name);for (i=0; i<device->num_axes; i++)g_print ("%g ", axes[i]);g_print ("\n");}}static gintbutton_press_event (GtkWidget *widget, GdkEventButton *event){current_device = event->device;cursor_proximity = TRUE;if (event->button == 1 && pixmap != NULL){gdouble pressure = 0.5;print_axes (event->device, event->axes);gdk_event_get_axis ((GdkEvent *)event, GDK_AXIS_PRESSURE, &pressure);draw_brush (widget, event->device->source, event->x, event->y, pressure);motion_time = event->time;}update_cursor (widget, event->x, event->y);return TRUE;}static gintkey_press_event (GtkWidget *widget, GdkEventKey *event){if ((event->keyval >= 0x20) && (event->keyval <= 0xFF))printf("I got a %c\n", event->keyval);elseprintf("I got some other key\n");return TRUE;}static gintmotion_notify_event (GtkWidget *widget, GdkEventMotion *event){GdkTimeCoord **events;int n_events;int i;current_device = event->device;cursor_proximity = TRUE;if (event->state & GDK_BUTTON1_MASK && pixmap != NULL){if (gdk_device_get_history (event->device, event->window, motion_time, event->time,&events, &n_events)){for (i=0; i<n_events; i++){double x = 0, y = 0, pressure = 0.5;gdk_device_get_axis (event->device, events[i]->axes, GDK_AXIS_X, &x);gdk_device_get_axis (event->device, events[i]->axes, GDK_AXIS_Y, &y);gdk_device_get_axis (event->device, events[i]->axes, GDK_AXIS_PRESSURE, &pressure);draw_brush (widget, event->device->source, x, y, pressure);print_axes (event->device, events[i]->axes);}gdk_device_free_history (events, n_events);}else{double pressure = 0.5;gdk_event_get_axis ((GdkEvent *)event, GDK_AXIS_PRESSURE, &pressure);draw_brush (widget, event->device->source, event->x, event->y, pressure);}motion_time = event->time;}if (event->is_hint)gdk_device_get_state (event->device, event->window, NULL, NULL);print_axes (event->device, event->axes);update_cursor (widget, event->x, event->y);return TRUE;}/* We track the next two events to know when we need to draw acursor */static gintproximity_out_event (GtkWidget *widget, GdkEventProximity *event){cursor_proximity = FALSE;update_cursor (widget, cursor_x, cursor_y);return TRUE;}static gintleave_notify_event (GtkWidget *widget, GdkEventCrossing *event){cursor_proximity = FALSE;update_cursor (widget, cursor_x, cursor_y);return TRUE;}voidinput_dialog_destroy (GtkWidget *w, gpointer data){*((GtkWidget **)data) = NULL;}voidcreate_input_dialog (void){static GtkWidget *inputd = NULL;if (!inputd){inputd = gtk_input_dialog_new ();g_signal_connect (inputd, "destroy",G_CALLBACK (input_dialog_destroy), &inputd);g_signal_connect_swapped (GTK_INPUT_DIALOG (inputd)->close_button,"clicked",G_CALLBACK (gtk_widget_hide),inputd);gtk_widget_hide (GTK_INPUT_DIALOG (inputd)->save_button);gtk_widget_show (inputd);}else{if (!GTK_WIDGET_MAPPED(inputd))gtk_widget_show(inputd);elsegdk_window_raise(inputd->window);}}voidquit (void){gtk_main_quit ();}JNIEXPORT void JNICALL Java_Demo_gtk_1draw(JNIEnv *env, jobject obj){int argc;char **argv;GtkWidget *window;GtkWidget *drawing_area;GtkWidget *vbox;GtkWidget *button;gtk_init (&argc, &argv);current_device = gdk_device_get_core_pointer ();window = gtk_window_new (GTK_WINDOW_TOPLEVEL);gtk_widget_set_name (window, "Test Input");gtk_widget_set_size_request(window , 300 , 200);gtk_container_set_border_width(GTK_CONTAINER(window) , 2);gtk_window_set_resizable(GTK_WINDOW(window) , FALSE);vbox = gtk_vbox_new (FALSE, 0);gtk_container_add (GTK_CONTAINER (window), vbox);gtk_widget_show (vbox);g_signal_connect (window, "destroy",G_CALLBACK (quit), NULL);/* Create the drawing area */drawing_area = gtk_drawing_area_new ();gtk_widget_set_size_request (drawing_area, 200, 200);gtk_box_pack_start (GTK_BOX (vbox), drawing_area, TRUE, TRUE, 0);gtk_widget_show (drawing_area);/* Signals used to handle backing pixmap */g_signal_connect (drawing_area, "expose_event",G_CALLBACK (expose_event), NULL);g_signal_connect (drawing_area, "configure_event",G_CALLBACK (configure_event), NULL);/* Event signals */g_signal_connect (drawing_area, "motion_notify_event",G_CALLBACK (motion_notify_event), NULL);g_signal_connect (drawing_area, "button_press_event",G_CALLBACK (button_press_event), NULL);g_signal_connect (drawing_area, "key_press_event",G_CALLBACK (key_press_event), NULL);g_signal_connect (drawing_area, "leave_notify_event",G_CALLBACK (leave_notify_event), NULL);g_signal_connect (drawing_area, "proximity_out_event",G_CALLBACK (proximity_out_event), NULL);gtk_widget_set_events (drawing_area, GDK_EXPOSURE_MASK| GDK_LEAVE_NOTIFY_MASK| GDK_BUTTON_PRESS_MASK| GDK_KEY_PRESS_MASK| GDK_POINTER_MOTION_MASK| GDK_POINTER_MOTION_HINT_MASK| GDK_PROXIMITY_OUT_MASK);/* The following call enables tracking and processing of extensionevents for the drawing area */gtk_widget_set_extension_events (drawing_area, GDK_EXTENSION_EVENTS_ALL);GTK_WIDGET_SET_FLAGS (drawing_area, GTK_CAN_FOCUS);gtk_widget_grab_focus (drawing_area);/* .. And create some buttons */button = gtk_button_new_with_label ("Input Dialog");gtk_box_pack_start (GTK_BOX (vbox), button, FALSE, FALSE, 0);g_signal_connect (button, "clicked",G_CALLBACK (create_input_dialog), NULL);gtk_widget_show (button);button = gtk_button_new_with_label ("Quit");gtk_box_pack_start (GTK_BOX (vbox), button, FALSE, FALSE, 0);g_signal_connect_swapped (button, "clicked",G_CALLBACK (gtk_widget_destroy),window);gtk_widget_show (button);gtk_widget_show (window);gtk_main ();}
然后用gcc编译生成动态链接库：
$ gcc -shared -fpic -o libGTK.so -I$JAVA_HOME/include -I$JAVA_HOME/include/linux 37_drawingPic3.c `pkg-config --cflags --libs gtk+-2.0`
最后用java连同动态链接库运行java的包含native方法的类的main函数：
$ java -Djava.library.path=. Demo
大功告成。
整体的编译过程是：
#!/bin/shjavac Demo_03_JButton_JPanel.javajavah -jni Demogcc -shared -fpic -o libGTK.so -I$JAVA_HOME/include -I$JAVA_HOME/include/linux 37_drawingPic3.c `pkg-config --cflags --libs gtk+-2.0`java -Djava.library.path=. Demo
