Panel

Using Panels
As you now realize, using Java's Layout Managers doesn't always produce desireable results. Using null layout is not cross platform. So, what can we do to get the best possible layout without resorting to null layout? Well, one answer is to use panels.

A panel can contain a panel which contains other panels or components. A panel can be set to use any layout manager. So, through a combination of using panels and layout managers, we should be able to achieve any layout we can imagine... maybe.

Below is an example applet that uses a bunch of panels. What you need to do is trace through the code and see where components are added to panels. Try to see how the applet layout which you see on the page is controlled by the commands in the code. You don't have to worry about anything but Panel stuff for this assignment. So, you can ignore some of the other stuff. Just try to see how all the stuff gets placed on the page.

Scoreboard Applet:

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

public class team extends Applet{
  TextField t1,t2,s1,s2;
  List l1, l2;
  Scrollbar sb1, sb2;
  Panel lt1, lt2, lt3, cent, rt;

public void init(){
    lt1 = new Panel();
    lt1.setSize(60,50);
    lt1.setLayout(new GridLayout(2,1));
    cent= new Panel();
    cent.setSize(100,100);
    cent.setLayout(new GridLayout(4,1));
    rt = new Panel();
    rt.setSize(60,50);
    rt.setLayout(new GridLayout(2,1));
    setBackground(Color.white);
    l1=new List(5,false);
    l1.addItem("Ballarat Bricks");
    l1.addItem("Argus Ants");
    l1.addItem("PP Pigeons");
    l1.addItem("Trona Termites");
    l1.setBackground(Color.cyan);
    l2=new List(5,false);
    l2.addItem("Ridgecrest Rats");
    l2.addItem("Inyokern Cats");
    l2.addItem("China Lake Cows");
    l2.addItem("Randsburg Bugs");
    l2.setBackground(Color.cyan);
    l1.addItemListener(new L1(this));
    l2.addItemListener(new L2(this));
    lt1.add(l1);
    lt1.add(l2);
    sb1=new Scrollbar(Scrollbar.HORIZONTAL, 0, 0, 0, 120);
    sb1.setBackground(Color.cyan);
    sb2=new Scrollbar(Scrollbar.HORIZONTAL, 0, 0, 0, 100);
    sb2.setBackground(Color.cyan);
    sb1.addAdjustmentListener(new SB1(this));
    sb2.addAdjustmentListener(new SB2(this));
    t1=new TextField(10);
    t2=new TextField(10);
    cent.add(t1);
    cent.add(sb1);
    cent.add(t2);
    cent.add(sb2);
    s1=new TextField(5);
    s2=new TextField(5);
    rt.add(s1);
    rt.add(s2);
    t1.setFont(new Font("Serif",Font.BOLD, 14));
    t2.setFont(new Font("Serif",Font.BOLD, 14));
    s1.setFont(new Font("Serif",Font.BOLD, 48));
    s2.setFont(new Font("Serif",Font.BOLD, 48));
    setLayout(new BorderLayout());
    Label top = new Label("TRONA DOME SCOREBOARD");
    top.setFont(new Font("Serif", Font.BOLD, 36));
    Label bottom = new Label("This scoreboard meets Earthquake Safety Standards");
    bottom.setFont(new Font("Serif", Font.PLAIN, 18));
    add(top, BorderLayout.NORTH);
    add(lt1, BorderLayout.WEST);
    add(cent, BorderLayout.CENTER);
    add(rt, BorderLayout.EAST);
    add(bottom, BorderLayout.SOUTH);
  }      
}

class SB1 implements AdjustmentListener{
  team T;

SB1(team t){
    T=t;
  }

public void adjustmentValueChanged(AdjustmentEvent e){
    int v=T.sb1.getValue();
    T.s1.setText(""+v);
  }
}

class SB2 implements AdjustmentListener{
  team T;

SB2(team t){
    T=t;
  }

public void adjustmentValueChanged(AdjustmentEvent e){
    int v=T.sb2.getValue();
    T.s2.setText(""+v);
  }
}

class L1 implements ItemListener{
  team T;

L1(team t){
    T=t;
  }

public void itemStateChanged(ItemEvent e){
    String s=T.l1.getSelectedItem();
    T.t1.setText(s);
  }
}

class L2 implements ItemListener{
  team T;

L2(team t){
    T=t;
  }

public void itemStateChanged(ItemEvent e){
    String s=T.l2.getSelectedItem();
    T.t2.setText(s);
  }
}

//<applet code=team.class height=200 width=400></applet>