import java.applet.Applet;  // need to inherit from built-in Applet
import java.awt.*;          // Window I/O classes
import java.awt.event.*;    // Event classes

// Dilip Barman  October 13, 1997
// file hw1Applet.java
// Oct.13 Got UI working
// Oct.16 With some help from Kenny Hoff, figured out the event model!

// 1st java homework assignment, to display a message.  We are to design
// a simple application that looks, initially, like:
//
// Display Message Applet
//   +--------------------------------------------------+
//   |       +--------+            +--------+           |
//   |       | display|            | clear  |           | 
//   |       +--------+            +--------+           |  
//   | +----------------------------------------------+ |
//   | |type message here                             | |
//   | +----------------------------------------------+ |
//   | +----------------------------------------------+ |
//   | |message display area                          | |
//   | +----------------------------------------------+ |
//   +--------------------------------------------------+
//
// The user can type anything in the "type message here" (initial string); when
// s/he presses the "display" button, the content of the first box is copied
// to the second box.  Whenever "clear" is pressed, both fields are cleared.  The
// whole application is light bluish-gray in color, except for the input message
// field, which is white.
//
// Architecturally, this is designed as 2 panels, since these run in the overall
// context of the applet and not as independent windows.


//
// Since this is an applet, it is meant to be run in a web browser.  First we compile
// the applet (javac hw1Applet.java) to get hw1Applet.class.  We can
// try it out via appletviewer (appletviewer hw1Applet.java) (note file type .java)
// or call it from an html page that has tags that look like:
//    <applet code="hw1Applet.class" width=50 height=50>
//    </applet>


public class hw1Applet 
  extends Applet 
  implements ActionListener
// We inherit from Applet and implement ActionListener methods 
// (i.e., respond to button events)

{

  // Instance and class variable definitions

  Panel topPanel    = new Panel();  // panel for buttons
  Panel mainPanel   = new Panel();  // panel for two <TextField>s

  Button displayButton = new Button ("display");
  Button clearButton   = new Button ("clear");
  TextField msgInputField  = new TextField("* type message here *", 40);
  TextField msgOutputField = new TextField("message display area", 40);

  
  // Now we define methods.  Applets look for 4 methods - init, start, stop, and destroy
  // init() is called when the applet is loaded, start() when it starts execution (i.e.,
  // right after init() and whenever we revisit this web page), stop() when we leave this
  // web page, and destroy() when we leave the browser.

  public void init()
    {
      //    setTitle ("Dilip's Display Message Applet");

      // Associate listeners to the two buttons.  We'll implement the
      // actions right here, so we call our own (this = self) methods.
    displayButton.addActionListener(this);  
    clearButton.addActionListener(this);  

    setBackground (Color.lightGray);
    setForeground (Color.black);  
  
    // Following two lines if we're not using separate panels - just add to applet  
    //    add (displayButton);
    //    add (clearButton);
    topPanel.add (displayButton);
    topPanel.add (clearButton);

    msgInputField.setBackground  (Color.white);
    msgInputField.setForeground  (Color.black);

    msgOutputField.setBackground (Color.lightGray);
    msgOutputField.setForeground (Color.black);
    msgOutputField.setEditable   (false);

    mainPanel.add (msgInputField);
    mainPanel.add (msgOutputField);

    // Now specify a layout manager - we'll use border layout
    setLayout (new BorderLayout());
    add ("North", topPanel);
    add ("Center", mainPanel);

    } 

  public void start()
    {
    System.out.println ("Starting applet ... \n");
    }

  public void stop()
    {
    System.out.println ("Stopping applet\n");
    }

  public void destroy()
    {
    System.out.println ("Destroying applet execution instance\n");
    }

  // Define an optional paint method.  This method gets called and
  // passed a pointer to the current graphics context whenever an
  // object is exposed.  The only reason I'm doing this is to add
  // a string of text.
  public void paint (Graphics g )  
    {

    g.setColor (Color.black);
    g.setFont (new Font ("Helvetica", Font.PLAIN, 14) );
    g.drawString ("Dilip's Display Message Applet", 0, 0);
    }  // end paint


  // Now define IMPLEMENTORS - override actionListener class's 
  // actionPerformed method.  It gets called whenever there is an action -
  // i.e., a button is pressed.  This is the only method we need
  // to implement. The basic logic is that if we've pressed displayButton,
  // copy msgInputField to msgOutputField.  Otherwise, clear msgOutputField.

  public void actionPerformed ( ActionEvent e )  
    {

      // Graphics g = this.getGraphics ();
    if (e.getActionCommand() == "display")
      {
        msgOutputField.setText (msgInputField.getText());
      }  // end handling DISPLAY
    else
      {
        msgInputField.setText ("");
        msgOutputField.setText ("");
      }  // end handling CLEAR

    }  // end actionPerformed


}  // end class definition