4.5 The TuttleTest demonstration class

To conclude this chapter the TuttleTest class which was used to provide the illustration in Figure 4.1 will be briefly introduced. The following chapters will present some more sophisticated interfaces for the Tuttle class. The implementation of this class as far as its init() method is as follows.

0001  // Filename TuttleTest.java. 0002  // First attempt at a Tuttle Interface, 0003  // interim version only. 0004  // 0005  // Written for the Java Interface Book Chapter 4. 0006  // Fintan Culwin, v 0.2, August 1997.  0007   0008   0009  import java.awt.*; 0010  import java.awt.event.*; 0011  import java.applet.*; 0012   0013  import Tuttles.Tuttle; 0014   0015   0016  public class TuttleTest extends    Applet 0017                          implements ActionListener { 0018   0019  private Tuttle theTuttle;  0020  private Label  feedbackLabel; 0021  private Panel  feedbackPanel;

The context imports the Tuttle class from the Tuttles package and the TuttleTest class is declared as implementing the ActionListener interface, as it will be its own listener when ActionEvents are generated by its buttons. Three instance attributes are delcare don lines 0019 to 0021: an instance of the Tuttle class called theTuttle, a Label called feedbackLabel and a Panel called feedbackPanel upon which it will be mounted.

0023     public void init() {  0024   0025     Panel  tuttlePanel, tuttleButtonsPanel; 0026     Button fwdButton, bwdButton, rtnButton, ltnButton, rstButton, 0027            clrButton, cstButton, fgrButton, fglButton, fgbButton,  0028            bgyButton, bgwButton, pdnButton, pupButton; 0029   0030        this.setLayout( new BorderLayout()); 0031   0032        tuttlePanel = new Panel(); 0033        tuttlePanel.setBackground( Color.white); 0034        theTuttle = new Tuttle( this, 400, 400); 0035        tuttlePanel.add( theTuttle); 0036         0037        tuttleButtonsPanel = new Panel(); 0038        tuttleButtonsPanel.setLayout( new GridLayout( 2, 7)); 0039   0040        fwdButton = new Button( "Fwd"); 0041        fwdButton.setActionCommand( "Fwd"); 0042        fwdButton.addActionListener( this); 0043        tuttleButtonsPanel.add( fwdButton); 0044         0045        bwdButton = new Button( "Bwd"); 0046        bwdButton.setActionCommand( "Bwd"); 0047        bwdButton.addActionListener( this); 0048        tuttleButtonsPanel.add( bwdButton);       ----        //Other Button construction and configuration omitted! 0114        feedbackPanel = new Panel(); 0115        feedbackPanel.setBackground( Color.white); 0116        feedbackLabel = new Label(); 0117        feedbackPanel.add( feedbackLabel); 0118         0119        this.add( tuttleButtonsPanel, "South");   0120        this.add( tuttlePanel,        "Center"); 0121        this.add( feedbackPanel,      "North"); 0122        this.feedback(); 0125     } // End init.

This method declares two Panels, which will be required for layout control on line 0025 and, on lines 0026 to 0028, the fourteen buttons which are shown at the bottom of the interface. The first part of the method, on line 0030, establishes a BorderLayout policy for the Applet. The Tuttle instance, theTuttle, is then created and mounted in its own Panel in lines 0032 to 0035.

Following this the Panel to mount the buttons on is created and its layout policy set to a 2 row by 7 column GridLayout. Each Button in turn is then created, has its ActionCommand attribute set, has the Applet registered as its ActionListener and is added to the tuttleButtonsPanel. Once all Buttons have been processed, lines 0114 to 0117 create the feedbackLabel and install it onto its own Panel. The init() method concludes by assembling the interface and calls the feedback() method, as follows, to produce the initial information display at the top of the interface.

0187     private void feedback() {     0188        feedbackLabel.setText( theTuttle.getDetails()); 0189        feedbackPanel.doLayout(); 0190     } // End feedback.

The feedback() method obtains the information it needs by calling theTuttle's getDetails() method and installs this String into the feedbackLabel, calling the feedbackPanel's doLayout() method to ensure that the size of the Label is changed, if necessary.

All ActionEvents generated by the Buttons are sent to the actionPerformed() method, which extracts the commandString from it and calls the appropriate Tuttle method with the required argument, if any, as follows. As indicated in the implementation a movement, forwards or backwards, is limited to 25 tuttle steps and a turn, right or left, to 30 degrees. This limitation will be addressed in the chapters which follow.

0129     public void actionPerformed( ActionEvent event) {  0130      0131     String itsCommand = event.getActionCommand(); 0132      0133        if ( itsCommand.equals("Fwd")) {  0134           theTuttle.forward( 25); 0135        } else if ( itsCommand.equals("Bwd")) {  0136           theTuttle.backward( 25); 0137        } else if ( itsCommand.equals("Rtn")) {  0138           theTuttle.turnRight( 30); ----           // Other branches omitted! 0176        } else if ( itsCommand.equals("Pup")) {  0177           theTuttle.setPenUp(); 0178        } // End if.  0179              0180        this.feedback(); 0181     } // End actionPerformed.

Pressing all of the buttons at the bottom of the interface will ensure that each of the methods which the Tuttle class offers is called at least once, thus producing an initial confidence that the Tuttle class seems to be working correctly.

TuttleTest.java

TuttleTest

Summary of Chapter 4

4.4 The TuttleCursor class