Question

I am currently doing the CS106A Stanford Java course for beginners. I am stuck at the handout number 7, requiring me to create a simple program that draws GRects with a GLabel on them on the canvas and then allows me to drag them around, remove them again or clear the whole canvas. In order to add such a box, I have added a JTextField in the SOUTH to enter the name of the box, and ADD / REMOVE / CLEAR buttons.

Entering a name into the textfield to add a box works. My problem is that the text I type into the JTextField, though recorded (since it shows up on the new box) is not displayed in the JTextField itself, so I do not see what I typed until I hit “ADD” and I read it on the box itself.

Here’s my code:

    package handout07Interactors;

import java.awt.Color;
import java.awt.event.ActionEvent;
import java.util.HashMap;

import javax.swing.*;

import acm.graphics.*;
import acm.program.*;

@SuppressWarnings("serial")
public class Box_Diagram extends GraphicsProgram{

    public void init() {
        displayButtons();
        addActionListeners();

        //TODO make draggable

    }

    public void actionPerformed(ActionEvent e) {

        if (e.getActionCommand().equals("ADD")) {

            //create box
            GCompound canvasBox = createBox(tf.getText());

            //add box to HashMap
            map.put(tf.getText(), canvasBox);

            //add box to canvas
            int x = (int) (getWidth() - canvasBox.getWidth()) / 2;
            int y = (int) (getHeight() - canvasBox.getHeight()) / 2;
            add(canvasBox, x, y);

        } else if (e.getActionCommand().equals("REMOVE")) {

            //remove box with name
            if (map.get(tf.getText()) != null) {remove(map.get(tf.getText()));}; //if box exists, remove it 

        } else {

            for( String name: map.keySet() )
            {
                remove(map.get(name));
            }



        }

    }

    private GCompound createBox(String text) {

        // GCompound
        GCompound box = new GCompound();

        // create GRect
        GRect rect = new GRect(BOX_WIDTH, BOX_HEIGHT);
        box.add(rect);

        // add GLabel
        GLabel label = new GLabel(text);
        int x = (int) (rect.getWidth() - label.getWidth()) / 2;
        int y = 30; //manual entry, somehow calculation didn't work as it does for width
        box.add(label, x, y);

        map.put(text, box);

        return box;

    }

    private void displayButtons() {

        //label
        add(new JLabel("Name:"), SOUTH);

        //textfield
        tf = new JTextField(30);
        tf.addActionListener(this);
        add(tf, SOUTH);

        //ADD REMOVE CLEAR
        add(new JButton("ADD"), SOUTH);
        add(new JButton("REMOVE"), SOUTH);
        add(new JButton("CLEAR"), SOUTH);

    }

    //IVARS
    private JTextField tf;
    public static final int BOX_WIDTH = 100;
    public static final int BOX_HEIGHT = 50;
    public HashMap<String, GCompound> map = new HashMap<String, GCompound>();



}

Answer 1

You’re adding 5 different components (the label, text field, and the 3 buttons) to the same place in the layout (the SOUTH section of your border layout).

You should add these 5 components to another JPanel, using a FlowLayout for example, and then add this panel to the SOUTH of your main panel.