The Java Native Interface (JNI) enabled developers to add platform-dependent functionality to Java applications. The JNI enables developers to add time-critical operations like mathematical calculations and 3D rendering. Previously, native 3D rendering was a problem because the native code didn't have access to the graphic context. The AWT Native Interface is designed to give developers access to an AWT Canvas for direct drawing by native code. In fact, the Java 3D API extension to the standard Java SEJDK relies heavily on the AWT Native Interface to render 3D objects in Java. The AWT Native Interface is very similar to the JNI, and, the steps are, in fact, the same as those of the JNI. See the Java Native Interface article for an explanation of the JNI techniques employed by the AWT Native Interface.
The AWT Native Interface was added to the Java platform with the J2SE 1.3 ("Kestrel") version.
AWT Native Interface example walkthrough
Create the Java application
Type in this in a .java file named JavaSideCanvas and compile:
See the Java Native Interface article for an explanation of the nativekeyword and the loadLibrary() method. The paint() method will be simply invoked when the AWT event dispatching thread "repaints" the screen.
It's interesting to note that the AWT Native Interface requires the "jawt.dll" (or "jawt.so") to run with the application, so the easiest way to do that is copying the "jawt.dll" (should be in the .../jre/bin file path of the JDK's installation path.)
You should see a window with a rectangle drawn in it.
Congratulations! You have made your first AWT Native Application!
As you can see, you can paint as if it is a native application. In Windows, the JVM will pass a HWND and other window information to your native application so that your application will "know" where to draw. In this example, it uses GDI to draw a Rectangle. The window information your native side need will be in a JAWT_Win32DrawingSurfaceInfo structure (depending on Operating System) which can be retrieved with this line: