A GridBagLayout Example

  void init () {
 
    GridBagLayout gbl = new GridBagLayout();
    this.setLayout(gbl);
    
    // Add the display to the top four cells
    GridBagConstraints displayConstraints = new GridBagConstraints();
    displayConstraints.gridx = 0;
    displayConstraints.gridy = 0;
    displayConstraints.gridwidth = 4;
    displayConstraints.gridheight = 1;
    displayConstraints.fill = GridBagConstraints.HORIZONTAL;
    
    // add the text field
    TextField display = new TextField(12);
    gbl.setConstraints(display, displayConstraints);
    this.add(display);

    // Add the clear button
    GridBagConstraints clearConstraints = new GridBagConstraints();
    clearConstraints.gridx = 0;
    clearConstraints.gridy = 1;
    clearConstraints.gridwidth = 1;
    clearConstraints.gridheight = 1;
    clearConstraints.fill = GridBagConstraints.BOTH;
    clearConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button clear = new Button("C");
    gbl.setConstraints(clear, clearConstraints);
    this.add(clear);

    
    // Add the equals button    
    GridBagConstraints equalsConstraints = new GridBagConstraints();
    equalsConstraints.gridx = 1;
    equalsConstraints.gridy = 1;
    equalsConstraints.gridwidth = 1;
    equalsConstraints.gridheight = 1;
    equalsConstraints.fill = GridBagConstraints.BOTH;
    equalsConstraints.insets = new Insets(3, 3, 3, 3);

    // add the = button
    Button equals = new Button("=");
    gbl.setConstraints(equals, equalsConstraints);
    this.add(equals);

    // Add the / button    
    GridBagConstraints slashConstraints = new GridBagConstraints();
    slashConstraints.gridx = 2;
    slashConstraints.gridy = 1;
    slashConstraints.gridwidth = 1;
    slashConstraints.gridheight = 1;
    slashConstraints.fill = GridBagConstraints.BOTH;
    slashConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button slash = new Button("/");
    gbl.setConstraints(slash, slashConstraints);
    this.add(slash);

    
    // Add the * button    
    GridBagConstraints timesConstraints = new GridBagConstraints();
    timesConstraints.gridx = 3;
    timesConstraints.gridy = 1;
    timesConstraints.gridwidth = 1;
    timesConstraints.gridheight = 1;
    timesConstraints.fill = GridBagConstraints.BOTH;
    timesConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button star = new Button("*");
    gbl.setConstraints(star, timesConstraints);
    this.add(star);

    // Add the 7 key
    GridBagConstraints sevenConstraints = new GridBagConstraints();
    sevenConstraints.gridx = 0;
    sevenConstraints.gridy = 2;
    sevenConstraints.gridwidth = 1;
    sevenConstraints.gridheight = 1;
    sevenConstraints.fill = GridBagConstraints.BOTH;
    sevenConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button b7 = new Button("7");
    gbl.setConstraints(b7, sevenConstraints);
    this.add(b7);

    
    // Add the 8 key    
    GridBagConstraints eightConstraints = new GridBagConstraints();
    eightConstraints.gridx = 1;
    eightConstraints.gridy = 2;
    eightConstraints.gridwidth = 1;
    eightConstraints.gridheight = 1;
    eightConstraints.fill = GridBagConstraints.BOTH;
    eightConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button b8 = new Button("8");
    gbl.setConstraints(b8, eightConstraints);
    this.add(b8);

    // Add the 9 key    
    GridBagConstraints nineConstraints = new GridBagConstraints();
    nineConstraints.gridx = 2;
    nineConstraints.gridy = 2;
    nineConstraints.gridwidth = 1;
    nineConstraints.gridheight = 1;
    nineConstraints.fill = GridBagConstraints.BOTH;
    nineConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button b9 = new Button("9");
    gbl.setConstraints(b9, nineConstraints);
    this.add(b9);

    
    // Add the - key    
    GridBagConstraints minusConstraints = new GridBagConstraints();
    minusConstraints.gridx = 3;
    minusConstraints.gridy = 2;
    minusConstraints.gridwidth = 1;
    minusConstraints.gridheight = 1;
    minusConstraints.fill = GridBagConstraints.BOTH;
    minusConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button minus = new Button("-");
    gbl.setConstraints(minus, minusConstraints);
    this.add(minus);
    
    // Add the 4 key
    GridBagConstraints fourConstraints = new GridBagConstraints();
    fourConstraints.gridx = 0;
    fourConstraints.gridy = 3;
    fourConstraints.gridwidth = 1;
    fourConstraints.gridheight = 1;
    fourConstraints.fill = GridBagConstraints.BOTH;
    fourConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button b4 = new Button("4");
    gbl.setConstraints(b4, fourConstraints);
    this.add(b4);

    
    // Add the 5 key    
    GridBagConstraints fiveConstraints = new GridBagConstraints();
    fiveConstraints.gridx = 1;
    fiveConstraints.gridy = 3;
    fiveConstraints.gridwidth = 1;
    fiveConstraints.gridheight = 1;
    fiveConstraints.fill = GridBagConstraints.BOTH;
    fiveConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button b5 = new Button("5");
    gbl.setConstraints(b5, fiveConstraints);
    this.add(b5);

    // Add the 6 key    
    GridBagConstraints sixConstraints = new GridBagConstraints();
    sixConstraints.gridx = 2;
    sixConstraints.gridy = 3;
    sixConstraints.gridwidth = 1;
    sixConstraints.gridheight = 1;
    sixConstraints.fill = GridBagConstraints.BOTH;
    sixConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button b6 = new Button("6");
    gbl.setConstraints(b6, sixConstraints);
    this.add(b6);

    
    // Add the + key    
    GridBagConstraints plusConstraints = new GridBagConstraints();
    plusConstraints.gridx = 3;
    plusConstraints.gridy = 3;
    plusConstraints.gridwidth = 1;
    plusConstraints.gridheight = 1;
    plusConstraints.fill = GridBagConstraints.BOTH;
    plusConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button plus = new Button("+");
    gbl.setConstraints(plus, plusConstraints);
    this.add(plus);    

    // Add the 1 key
    GridBagConstraints oneConstraints = new GridBagConstraints();
    oneConstraints.gridx = 0;
    oneConstraints.gridy = 4;
    oneConstraints.gridwidth = 1;
    oneConstraints.gridheight = 1;
    oneConstraints.fill = GridBagConstraints.BOTH;
    oneConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button b1 = new Button("1");
    gbl.setConstraints(b1, oneConstraints);
    this.add(b1);

    
    // Add the 2 key    
    GridBagConstraints twoConstraints = new GridBagConstraints();
    twoConstraints.gridx = 1;
    twoConstraints.gridy = 4;
    twoConstraints.gridwidth = 1;
    twoConstraints.gridheight = 1;
    twoConstraints.fill = GridBagConstraints.BOTH;
    twoConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button b2 = new Button("2");
    gbl.setConstraints(b2, twoConstraints);
    add(b2);

    // Add the 3 key    
    GridBagConstraints threeConstraints = new GridBagConstraints();
    threeConstraints.gridx = 2;
    threeConstraints.gridy = 4;
    threeConstraints.gridwidth = 1;
    threeConstraints.gridheight = 1;
    threeConstraints.fill = GridBagConstraints.BOTH;
    threeConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button b3 = new Button("3");
    gbl.setConstraints(b3, threeConstraints);
    this.add(b3);

    
    // Add the = key    
    GridBagConstraints bigEqualsConstraints = new GridBagConstraints();
    bigEqualsConstraints.gridx = 3;
    bigEqualsConstraints.gridy = 4;
    bigEqualsConstraints.gridwidth = 1;
    bigEqualsConstraints.gridheight = 2;
    bigEqualsConstraints.fill = GridBagConstraints.BOTH;
    bigEqualsConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button bigEquals = new Button("=");
    gbl.setConstraints(bigEquals, bigEqualsConstraints);
    this.add(bigEquals);
    
    // Add the 0 key
    GridBagConstraints zeroConstraints = new GridBagConstraints();
    zeroConstraints.gridx = 0;
    zeroConstraints.gridy = 5;
    zeroConstraints.gridwidth = 2;
    zeroConstraints.gridheight = 1;
    zeroConstraints.fill = GridBagConstraints.BOTH;
    zeroConstraints.insets = new Insets(3, 3, 3, 3);
    
    // add the button
    Button b0 = new Button("0");
    gbl.setConstraints(b0, zeroConstraints);
    this.add(b0);

    
    // Add the . key    
    GridBagConstraints decimalConstraints = new GridBagConstraints();
    decimalConstraints.gridx = 2;
    decimalConstraints.gridy = 5;
    decimalConstraints.gridwidth = 1;
    decimalConstraints.gridheight = 1;
    decimalConstraints.fill = GridBagConstraints.BOTH;
    decimalConstraints.insets = new Insets(3, 3, 3, 3);

    // add the button
    Button bdecimal = new Button(".");
    gbl.setConstraints(bdecimal, decimalConstraints);
    this.add(bdecimal);

  }