import objectdraw.*;
import java.awt.*;
import java.awt.event.*;

/**
 * Demonstrates use of button, text field, and label widgets, panels,
 * flow and border layout, and key listening with focus management.
 * 
 * A vertical bar is displayed in the canvas area with X coordinate determined
 * by the displayed value, which is incremented and decremented by a given change
 * amount using the arrow keys. The change amount can be modified with the text
 * field, and the value may be reset to its initial setting with a reset button.
 */
public class GuiDemo extends FrameWindowController
   implements KeyListener, ActionListener, FocusListener {
   
   private static final int INIT_INCREMENT = 10;
   private static final int INIT_VALUE = 100;
   
   private int value = INIT_VALUE;
   private int change = INIT_INCREMENT;
   
   private Label valueLabel;
   private Button reset;
   private TextField changeField;
   
   private FilledRect rect;
      
   public void begin() {   
      // the following widgets can't be created before begin is called
      rect = new FilledRect(value, 0, 10, 1000, canvas);    
      reset = new Button("Reset value");
      valueLabel = new Label("     "); // 5 spaces for adequate label length
      changeField = new TextField("" + INIT_INCREMENT);
      
      Panel panel = new Panel();  
      panel.add(new Label("Value:"));
      panel.add(valueLabel);
      panel.add(reset);
      panel.add(new Label("Change:"));
      panel.add(changeField);
      
      // use the default FlowLayout layout manager
      add(panel, BorderLayout.NORTH);      
      add(new Label("Use right and left arrow keys to increment and deccrement."),
          BorderLayout.SOUTH);
      // the canvas is in the center of the layout
       
      // add all the listeners
      reset.addActionListener(this);
      changeField.addActionListener(this);      
      changeField.addFocusListener(this);
      canvas.addKeyListener(this);
      
      validate(); // need this or widgets don't show up until frame is resized
      // w/o the following key events aren't recognized until you click on the canvas
      focusOnCanvas();       
      
      setValue(INIT_VALUE);
   }
   
   // implement ActionListener
   public void actionPerformed(ActionEvent e) {
      if (e.getSource() == changeField) {
         change = Integer.parseInt(changeField.getText());
      }
      else setValue(INIT_VALUE); // source is reset button  
      focusOnCanvas();
   }
   
   // implement KeyListener
   public void keyPressed(KeyEvent e) {
      switch (e.getKeyCode()) {
         case KeyEvent.VK_LEFT: {
            setValue(value - change); 
            break;
         }
         case KeyEvent.VK_RIGHT: {
            setValue(value + change);
            break;
         }
      }
   }   
   public void keyReleased(KeyEvent e) {}     
   public void keyTyped(KeyEvent e) {}
   
   // implement FocusListener
   public void focusGained(FocusEvent e) {}
   public void focusLost(FocusEvent e) {
      focusOnCanvas();
   }
   
   private void setValue(int value) {
      this.value = value;
      valueLabel.setText("" + value);
      rect.moveTo(value, 0);
   }
   
   /* Force the keyboard listener focus to be on the objectdraw canvas.
    * 
    * You don't want to know how this works, other than noting that it
    * uses getAppletFrame, so it has to be in the FrameWindowController class.
    */
   private void focusOnCanvas() {
      ((AWTDrawingCanvas)getAppletFrame().getAccessibleContext()
          .getAccessibleChild(0).getAccessibleContext().getAccessibleChild(0))
         .requestFocus(); 
   }
}