/*Note: still incomplete. Needs graphical view of the tree implemented. */ import java.awt.*; import java.awt.event.*; /** * An applet to sort and store DictionaryEntries using a BinarySearchTree * * @author Zach Tomaszewski * @version 24 November */ public class BSTApplet extends java.applet.Applet implements ActionListener { private BinarySearchTree bst = new BinarySearchTree(); private TextArea displayArea; private Panel displayPanel; private Button add; private Button remove; private Button clearList; private Button display; private Button statusOK; private TextField statusLine; private TextField wordEntry; private TextField defEntry; private final static Color BACKGROUND = new Color(00,00,65); private final static Color FOREGROUND = Color.white; /** * Initializes the applet by creating the GUI. */ public void init() { this.setLayout(new BorderLayout()); this.add(this.getGUI(), BorderLayout.CENTER); this.setStatusLine(null); } /** * Returns a panel containing the graphical interface * components for this applet. Includes a brief intro * message explaining the use of the applet. */ protected Panel getGUI() { Panel gui = new Panel(new BorderLayout()); Panel north = new Panel(new FlowLayout(FlowLayout.LEFT)); String welcome = "Dictionary/BST Applet.\n"; welcome = welcome + "\nYou can Add and Remove dictionary entries below, "; welcome = welcome + "and you will see them displayed here.\n"; welcome = welcome + "\nDuplicate entries or the empty string (\"\") are " + "not supported. You need to enter only the word to " + "remove an entry from the list."; displayArea = new TextArea(welcome, 10, 40, TextArea.SCROLLBARS_VERTICAL_ONLY); displayArea.setEditable(false); displayArea.setBackground(FOREGROUND); displayPanel = new Panel(new FlowLayout()); displayPanel.add(displayArea); north.add(displayPanel); Panel northEast = new Panel(new GridLayout(2, 1)); display = new Button("Display Tree"); display.setActionCommand("display"); display.addActionListener(this); display.setEnabled(false); clearList = new Button("Clear List"); clearList.setActionCommand("clearList"); clearList.addActionListener(this); clearList.setEnabled(false); northEast.add(display); northEast.add(clearList); north.add(northEast); gui.add(north, BorderLayout.NORTH); Panel center = new Panel(new FlowLayout(FlowLayout.LEFT)); Panel centerGrid = new Panel(new GridLayout(3,1)); Panel row1 = new Panel(new FlowLayout(FlowLayout.RIGHT)); Label word = new Label("Word: ", Label.RIGHT); word.setForeground(FOREGROUND); row1.add(word); wordEntry = new TextField("", 16); wordEntry.setBackground(Color.white); row1.add(wordEntry); centerGrid.add(row1); Panel row2 = new Panel(new FlowLayout(FlowLayout.RIGHT)); Label def = new Label("Definition: ", Label.RIGHT); def.setForeground(FOREGROUND); row2.add(def); defEntry = new TextField("", 16); defEntry.setBackground(Color.white); row2.add(defEntry); centerGrid.add(row2); Panel row3 = new Panel(new FlowLayout(FlowLayout.CENTER)); add = new Button("Add"); add.setActionCommand("add"); add.addActionListener(this); row3.add(add); remove = new Button("Remove"); remove.setActionCommand("remove"); remove.addActionListener(this); remove.setEnabled(false); row3.add(remove); centerGrid.add(row3); center.add(centerGrid); gui.add(center, BorderLayout.CENTER); GridBagLayout southGridBag = new GridBagLayout(); GridBagConstraints constr = new GridBagConstraints(); Panel south = new Panel(southGridBag); statusLine = new TextField(""); statusLine.setEnabled(false); constr.anchor = constr.WEST; constr.fill = constr.HORIZONTAL; constr.weightx = 1; southGridBag.setConstraints(statusLine, constr); south.add(statusLine); constr = new GridBagConstraints(); statusOK = new Button("OK"); statusOK.setActionCommand("statusOK"); statusOK.addActionListener(this); southGridBag.setConstraints(statusOK, constr); south.add(statusOK); gui.add(south, BorderLayout.SOUTH); gui.setBackground(BACKGROUND); return gui; } /* action listener's method; handles all buttons in the applet; docs inherited from ActionListener*/ public void actionPerformed (ActionEvent ae) { String command = ae.getActionCommand(); if (command.equals("statusOK")) { //cleaning up after an error this.setStatusLine(null); } if (command.equals("add") ) { String word = wordEntry.getText(); String def = defEntry.getText(); try { if (!word.equals("")) { bst.insert(new DictionaryEntry(word,def)); this.updateDisplay(); this.updateButtonStates(); }else { this.setStatusLine("Error: can't add empty string."); } }catch (BSTException bst) { this.setStatusLine("Error: could not add your entry. "+ "Perhaps it is already in the list."); } } if (command.equals("remove") ) { String word = wordEntry.getText(); try { bst.remove(new DictionaryEntry(word, "")); this.updateDisplay(); this.updateButtonStates(); }catch (BSTException bst) { this.setStatusLine("Error: could not find/remove your entry."); } } if (command.equals("clearList") ) { bst.removeAll(); this.updateDisplay(); this.updateButtonStates(); } if (command.equals("display") ) { if (display.getLabel().equals("Display Tree")) { //switch view display.setLabel("Display List"); this.updateDisplay(); }else { display.setLabel("Display Tree"); this.updateDisplay(); } } } /** * Displays the given message in the status line, reveals statusOK button, * and disables all other controls. * If the given status is null, will reenable all controls * (using updateButtonStates) and hide statusOK. * * @param status the message to display, or else null */ protected void setStatusLine(String status) { if (status == null) { //no error message to display statusLine.setText(""); statusLine.setBackground(BACKGROUND); //blur out statusOK.setVisible(false); wordEntry.setBackground(FOREGROUND); //can be seen wordEntry.setEnabled(true); //ready for input defEntry.setBackground(FOREGROUND); //can be seen defEntry.setEnabled(true); //ready for input this.updateButtonStates(); //turn everything back on }else { statusLine.setText(status); statusLine.setBackground(FOREGROUND); //blur in wordEntry.setBackground(BACKGROUND); //blur out defEntry.setBackground(BACKGROUND); //blur out statusOK.setVisible(true); display.setEnabled(false); clearList.setEnabled(false); remove.setEnabled(false); add.setEnabled(false); } //to get statusOK to actually show up Container panel = statusOK.getParent(); panel.validate(); } /** * Updates all control buttons to their appropriate "enabled" state, based on the * contents of the list. If there are no contents of the list, all buttons * but Add are disabled. Otherwise, all are enabled. * Does not affect the statusOK button one way or the other. */ protected void updateButtonStates () { boolean canRemove = !bst.isEmpty(); //FIX: display disabled until view change is written display.setEnabled(false); //canRemove; clearList.setEnabled(canRemove); remove.setEnabled(canRemove); add.setEnabled(true); } /** * Refreshes the display of the list to display area * and clears the input text fields. */ protected void updateDisplay() { displayArea.setText(bst.toString()); wordEntry.setText(""); defEntry.setText(""); } }//end class