Java Programming Challenge: Creating a GUI Calculator-Like Interface

Question

This is probably an elementary question. However, I have completed reading the 7th Chapter of Java Programming for the Absolute Beginner and have approached the Challenges section. I cannot quite get the clear button to work for the challenge question.

The question asks:

Create a numerical keypad that uses Buttons to update an uneditable TextField by appending the clicked number to the end of its current number. Use a BorderLayout for the Frame. At BorderLayout.NORTH, place the TextField. In the center, create a panel that uses a GridLayout to lay out Buttons 1 through 9 in a three by three grid. At BorderLayout.SOUTH, create another Panel that has the zero key and also a “clear” key that deletes the current number in the TextField."

I think that my main problem is within the TextArea append method. I know that I was supposed to use a TextField, however it seems to be impossible to append within a TextField according to research I have done.

An answer to this question can potentially aid many new Java programmers in understanding basic GUI and Event Handling.

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

public class CalcFacade extends GUIFrame
                                    implements ActionListener, TextListener {

TextField tf;
TextArea ta;
Panel p1, p2;
Label clear;
Button b1, b2, b3, b4, b5, b6, b7, b8, b9, c, b0;
public CalcFacade() {
    super("Calculator Facade");
    setLayout(new BorderLayout());

Button b1 = new Button("1");
b1.addActionListener(this);
Button b2 = new Button("2");
b2.addActionListener(this);
Button b3 = new Button("3");
b3.addActionListener(this);
Button b4 = new Button("4");
b4.addActionListener(this);
Button b5 = new Button("5");
b5.addActionListener(this);
Button b6 = new Button("6");
b6.addActionListener(this);
Button b7 = new Button("7");
b7.addActionListener(this);
Button b8 = new Button("8");
b8.addActionListener(this);
Button b9 = new Button("9");
b9.addActionListener(this);

Button b0 = new Button("0");
b0.addActionListener(this);

Button c = new Button("Clear");
c.addActionListener(new ActionListener() {
    public void actionPerformed(ActionEvent e) {
    clear.setText("");
}
});
    tf = new TextField(100);
add(tf);
tf.setEnabled(false);
tf.addActionListener(this);
tf.addTextListener(this);
setVisible(false);

ta = new TextArea("", 10, 30);
    add(ta);
    ta.setEnabled(true);
    setVisible(true);


Panel p1 = new Panel();
p1.setLayout(new GridLayout(3, 3));
p1.setBackground(Color.gray);
p1.add(b1);
p1.add(b2);
p1.add(b3);
p1.add(b4);
p1.add(b5);
p1.add(b6);
p1.add(b7);
p1.add(b8);
p1.add(b9);

Panel p2 = new Panel();
p2.setBackground(Color.gray);
p2.add(b0);
p2.add(c);

add(ta, BorderLayout.NORTH);
add(p1, BorderLayout.CENTER);
add(p2, BorderLayout.SOUTH);

pack();
setSize(400, 300);
setVisible(true);
}

public static void main(String args[]) {
    CalcFacade cf = new CalcFacade();
}
public void actionPerformed(ActionEvent e) {
   tf.setText(""
    +((Button)e.getSource()).getLabel());
}

public void textValueChanged(TextEvent e) {
    ta.append(tf.getText());
}
}

I thank you very much ahead of time for all of your assistance.

In order to append, set the text to what was previously there + the label of the pressed button: `tf.setText(tf.getText() + ((Button)e.getSource()).getLabel())`. The clear buttons just set the textfield to an empty value `tf.setText("")` — Alex, Dec 28 '12 at 22:24
Follow this link. This might help you solve your issue. [Click here](http://stackoverflow.com/questions/14062467/retrieve-values-from-database-and-show-in-textfield/14062825#14062825) — Smit, Dec 28 '12 at 22:29

score 1 · Accepted Answer · answered Dec 29 '12 at 02:06

The TextField dosen't need to listen for an event just the buttons.

To add the number to the end just set the text to what's already in the TextField plus the button label.

Just one ActionListener and one actionPerformed method; identify the button and set the TextField appropriately i.e c.addActionListener(this);

public void actionPerformed(ActionEvent e)
{
    Button b = (Button) e.getSource();

    if (b.getLabel().equals("Clear"))
    {
        tf.setText("");
    }
    else
    {
        tf.setText(tf.getText() + b.getLabel());
    }
}

score 0 · Answer 2 · answered Dec 28 '12 at 22:28

0

Looks like the ActionListener for your "Clear" button is calling setText("") on Label clear, when I'm guessing you want to call it on TextField tf.

answered Dec 28 '12 at 22:28

Reinstate Monica -- notmaynard

5,464
2
26
42

Java Programming Challenge: Creating a GUI Calculator-Like Interface

2 Answers2