4. AWT 1.1 Containers

4. AWT 1.1 Containers
	Chapter 23. Extra: Graphic User Interface - AWT

4.1. Frames

The Frame class provides windows for applets and applications. Every application needs at least one Frame.

4.1.1. Code Example

public class MenuWindow extends Frame {
       boolean inAnApplet = true;
       TextArea output;

       public MenuWindow() {
              //Calls the Frame constructor and adds components to the window
              addWindowListener(new WindowAdapter() {
                   public void windowClosing(WindowEvent e) {
                      if (inAnApplet) {
                          dispose();
                      } else {
                          System.exit(0);
                      }
                   }
              }

         . . .

         public static void main(String args[]) {
                MenuWindow window = new MenuWindow();
                window.inAnApplet = false;
                window.setTitle("MenuWindow Application");
                window.setSize(450, 200);
                window.setVisible(true);
         }
}

4.1.2. Other methods provided by Frame

String getTitle() and void setTitle(String)
Returns or sets (respectively) the title of the frame's window.
Image getIconImage() and void setIconImage(Image)
Returns or sets (respectively) the image displayed when the window is iconified.
MenuBar getMenuBar() and void setMenuBar(MenuBar)
Returns or sets (respectively) the menu bar for this Frame.
void remove(MenuComponent)
Removes the specified menu bar from this Frame.

4.2. Panels

The Panel class is a general-purpose Container subclass. You can use it as-is to hold Components, or you can define a subclass to perform special functionality, such as event handling for the objects the Panel contains.

	Note
	The Applet class is a Panel subclass with special hooks to run in a browser or other applet viewer.

4.2.1. Code Example

Panel p1 = new Panel();
p1.add(new Button("Button 1"));
p1.add(new Button("Button 2"));
p1.add(new Button("Button 3"));

A Panel subclass that draws a frame around its contents.

Figure 23.16. Panel Subclass

class FramedArea extends Panel {
    public FramedArea(CoordinatesDemo controller) {
        ...//Set the layout manager.
           //Add any Components this Panel contains...
    }

    //Ensure that no Component is placed on top of the frame.
    //The inset values were determined by trail and error.
    public Insets getInsets() {
        return new Insets(4,4,5,5);
    }

    //Draw the frame at this Panel's edges.
    public void paint(Graphics g) {
        Dimension d = getSize();
        Color bg = getBackground();
 
        g.setColor(bg);
        g.draw3DRect(0, 0, d.width - 1, d.height - 1, true);
        g.draw3DRect(3, 3, d.width - 7, d.height - 7, false);
    }
}

4.3. Dialogs

The AWT provides support for dialogs -- windows that are dependent on other windows -- with the Dialog class. It provides a useful subclass, FileDialog,that provides dialogs to help the user open and save files.

Figure 23.17. Dialog

4.3.1. Code Example

class SimpleDialog extends Dialog implements ActionListener {
      TextField field;
      DialogWindow parent;
      Button setButton;

      SimpleDialog(Frame dw, String title) {
            super(dw, title, false);
            parent = (DialogWindow)dw;
           
            ...//Create and add components, such as the set button.
           
            //Initialize this dialog to its preferred size.
            pack();
      }

      public void actionPerformed(ActionEvent event) {
             Object source= event.getSource();
             if ((source == setButton) | (source == field))
                      parent.setText(field.getText());
             field.selectAll();
             setVisible(false);
      }
}
     
//Here's the code that brings up the dialog: 

if (dialog == null)
   dialog = new SimpleDialog(this, "A Simple Dialog");

dialog.setVisible(true);