import java.applet.*;
import java.awt.*;
import java.awt.event.*;

/**
 * Demonstrates the basic use of each of the various Components ("widgets")
 * that can be used in an Applet. This code is broken into three sections:
 * <OL>
 *   <LI>Constructing the widgets. To enable access from other classes
 *       (including inner classes), the Components should be declared
 *       as instance variables of this class, though they may be
 *       defined (constructed) in the init() method, if desired.</LI>
 *   <LI>Inside init(), layout is done by adding the Components to the
 *       appropriate Containers.</LI>
 *   <LI>Also inside init(), the listeners are added to each component.</LI>
 * </OL>
 * It might seem to make more sense to organize the code widget by widget,
 * but it turns out to be much easier to design and fiddle with the layout
 * if all the add() messages are together in one place.
 *
 * @author David Matuszek
 * @version November 11, 2001
 */
public class Widgets extends Applet {

    // Declare components here to avoid access problems.
    Label label = new Label("This is a Label");
    Button button = new Button("Button");
    Button changeButton = new Button("Change things");
    Checkbox checkbox = new Checkbox("Single Checkbox");
    Choice choice = new Choice();
    List list = new List(3); // 3 rows visible
                       // new Scrollbar(orientation, value, bubblesize, min, max)
    Scrollbar scrollbar = new Scrollbar(Scrollbar.HORIZONTAL, 50, 10, 0, 110);
    TextField textField = new TextField("This is a TextField.", 20);
    TextArea textArea = new TextArea("This is a TextArea.\nIt's about 20 n's wide:\n" +
                                      "nnnnnnnnnnnnnnnnnnnn\n" +
                                      "and 5 lines tall.\n" +
                                      "Here are 20 iiiiiiiiiiiiiiiiiiii's", 5, 20,
                                      TextArea.SCROLLBARS_NONE);
    CheckboxGroup checkboxGroup = new CheckboxGroup();
        Checkbox checkbox1 = new Checkbox("Checkbox 1", true,  checkboxGroup);
        Checkbox checkbox2 = new Checkbox("Checkbox 2", false, checkboxGroup);
        Checkbox checkbox3 = new Checkbox("Checkbox 3", false, checkboxGroup);
        Checkbox checkbox4 = new Checkbox("Checkbox 4", false, checkboxGroup);

    /**
     * Creates the GUI.
     */
    public void init() {
  
        // Lay out the widgets.
        // Add choices (Strings) to the Choice component
        choice.add("choice 1");
        choice.add("choice 2");
        choice.add("choice 3");
        choice.add("choice 4");
    
        // Add list elements (Strings) to the List component
        list.add("list 1");
        list.add("list 2");
        list.add("list 3");
        list.add("list 4");
        list.add("list 5");
    
        // Add remaining components, including choice and list, to the Applet
        add(label);
        add(button);
        add(checkbox);
        add(choice);
        add(scrollbar);
        add(list);
        add(textField);
        add(textArea);
        // Add individual checkboxes, NOT add (checkboxGroup);
        add(checkbox1);
        add(checkbox2);
        add(checkbox3);
        add(checkbox4);
        // The changeButton modifies a number of things in the GUI
        add(changeButton);
        changeButton.setBackground(Color.orange);
    
        // Assign listeners to widgets.

        // Button
        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                showStatus("Button clicked.");
            }
        });

        // Checkbox
        checkbox.addItemListener(new ItemListener() {
        public void itemStateChanged(ItemEvent event) {
            showStatus("Checkbox status is now " +
                       (event.getStateChange() == ItemEvent.SELECTED));
            }
        });

        // Choice (drop-down list)
        choice.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent event) {
                showStatus("Choice: " + choice.getSelectedItem());
            }
        });

        // List
        list.addItemListener(new ItemListener() {
            public void itemStateChanged(ItemEvent event) {
                showStatus("List: " + list.getSelectedItem());
            }
        });
    
        // Scrollbar
        scrollbar.addAdjustmentListener(new AdjustmentListener() {
            public void adjustmentValueChanged(AdjustmentEvent event) {
                showStatus("Scrollbar: " + scrollbar.getValue());
            }
        });

        // TextField
        textField.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                showStatus("TextField(ActionListener): " + textField.getText());
            }
        });
        textField.addTextListener(new TextListener() {
            public void textValueChanged(TextEvent event) {
                showStatus("TextField(TextListener): " + textField.getText());
            }
        });
    
        // TextArea
        textArea.addTextListener(new TextListener() {
            public void textValueChanged(TextEvent event) {
                showStatus("TextArea: " + textArea.getText());
            }
        });

        // Button -- to demonstrate changing values programmatically
        changeButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                label.setText("Changed label");
                textField.setText("This text is changed");
                textArea.setText("The text in this TextArea\nhas been changed");

                changeButton.setLabel("Already changed.");
                changeButton.setEnabled(false);

                checkbox.setLabel("Destroy world");
                checkbox.setState(true);

                choice.select("choice 3");
                list.select(0);

                scrollbar.setValue(100 - scrollbar.getValue());
                checkbox3.setState(true);
            }
        });

        // Checkboxes in a CheckboxGroup
        MyGroupListener myGroupListener = new MyGroupListener(); // see below
        checkbox1.addItemListener(myGroupListener);
        checkbox2.addItemListener(myGroupListener);
        checkbox3.addItemListener(myGroupListener);
        checkbox4.addItemListener(myGroupListener);
        
        // set initial applet size (appletviewer only)
        setSize(485, 200);
    } // end init()


    /**
     * Listener for the checkboxGroup. Implemented as a member class instead
     * of an anonymous inner class because it is used several times.
     */
    class MyGroupListener implements ItemListener {
        public void itemStateChanged(ItemEvent event) {
            Checkbox d = checkboxGroup.getSelectedCheckbox();
        showStatus("CheckboxGroup: " + d.getLabel());
        }
    }
}