James Weaver on Quantum Computing and Java

Answering Reader Mail about the JavaFX Reflection API

Sarah H comments on a blog post:

Hi again, you said "Also, JavaFX has reflection." sorry,but i didn't understand very well..can u make it a little bit more clear ? besides is there something similar to "Class.forName(str).getInstance();" but in JavaFX ? and who can also handle the properties like for example in the case of a SwingButton(text,action..) Thanks

Sarah (and anyone else that is curious about reflection in JavaFX),

That's a very good question, and there is very little documentation on this subject so far.  Here's a quick example of using the reflection API in JavaFX.  First a screenshot:

When you first invoke the program, only the button appears.  Each time you click the button, an instance of a TextBox is created using classes in the javafx.reflect package.  Each instance is added to the content sequence of a VBox layout container which causes each new TextBox to appear below the previous one.  Take a look at the code below while browsing the javafx.reflect package in the JavaFX API docs to see what's going on in this program.  Here's the code:

/*
 * ReflectExample1Main.fx
 *
 * Developed 2009 by James L. Weaver as a very simple example of
 * using the javafx.reflect package in JavaFX
 */

package javafxpert.reflectexample.ui;

import java.util.Date;
import java.util.Iterator;
import javafx.reflect.*;
import javafx.stage.Stage;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.ext.swing.SwingButton;

Stage {
  var sceneRef: Scene;
  title: "Reflection"
  scene:
  sceneRef = Scene {
    var vBoxRef:VBox;
    width: 500
    height: 500
    content: [
      SwingButton {
        translateX: 10
        translateY: 10
        text: "Create TextBox"
        action: function():Void {
          // Now use reflection to create a TextBox object
          // First, get the local context
          var ctx:FXLocal.Context = FXLocal.getContext();

          // Then, get an object that represents the class type
          var cls:FXLocal.ClassType = ctx.findClass("javafx.scene.control.TextBox");

          // Just for grins, print the variable names of the TextBox class
          var varIter:Iterator = cls.getVariables(true).iterator();
          while (varIter.hasNext()) {
            println(varIter.next());
          }

          // Now, create an object that represents the TextBox object
          var objVal:FXObjectValue =  cls.allocate();

          // Initialize variables of the object
          var now:String = new Date().toString();
          objVal.initVar("text", ctx.mirrorOf(now));
          objVal.initVar("columns", ctx.mirrorOf(20.0));

          // Initialize the TextBox object
          objVal = objVal.initialize();

          // Get the JavaFX reference to the TextBox
          var node: Node = ((objVal as FXLocal.ObjectValue).asObject()) as Node;

          // Insert this TextBox node into the VBox by appending it to
          // the content sequence
          insert node into vBoxRef.content;
        }
      },
      vBoxRef = VBox {
        translateX: 200
        translateY: 10
        spacing: 5
      }
    ]
  }
}

As you can see, the reflection API enables capabilities such as dynamic generation of forms based upon data structures known only at runtime.  There will be more information about the JavaFX reflection API next week in the Pro JavaFX Platform book (which is available in eBook form through the Apress Alpha program).

Regards,
Jim Weaver

Pro JavaFX Released in Apress Alpha (Early Access) Program

As many of you know, Weiqi Gao, Stephen Chin, Dean Iverson and I have been writing a book entitled  Pro JavaFX that is targeted at serious developers who want to use JavaFX.  In addition to the book being available in printed form by JavaOne 2009, we made the decision last week to allow the book to be offered as an Apress Alpha (early access) eBook.  This enables you to see the chapters of the book as drafts are submitted and revised, which gives you access to the content as soon as it is created (typos and all).  This also enables us to fine-tune the material based upon your feedback.

Here's the list of the chapters for the book:

1. Getting a Jump Start in JavaFX
2. Taking a Closer look at the JavaFX Language
3. Creating a User Interface in JavaFX
4. Using Functions, Classes and Other Advanced Features
5. Creating Custom UI Components in JavaFX
6. Using the Media Classes
7. Dynamically Laying out Nodes in the User Interface
8. Extending JavaFX with Third-Party Libraries
9. Building a Professional JavaFX Application
10. Developing JavaFX Mobile Applications

Currently, seven chapters (1, 2, 3, 4, 6, 7, 8) are available for download, and each of these is in first or second draft.  Chapters 5, 9 and 10 will be available soon as first drafts.  Here is a screenshot from Chapter 8 in which a drawing program built in JavaFX (in Chapter 5) is used to draw the shapes available in the JFXtras project:

Weiqi, Stephen, Dean and I welcome you to join us in this journey as we complete the development of what is becoming a definitive treatment of JavaFX for professional developers.

For therapeutic purposes I'm sure, Stephen Chin wrote a quick blog post that gives an "exclusive, behind-the-scenes look into the making of the Pro JavaFX™ Platform book" :-)

Regards,
Jim Weaver
JavaFXpert.com