CODEWITHSUNDEEP
javaswinguser-interfacejframe
AvivC
AvivC

Reputation: 133

Graphic elements won't apear in JFrame (Java)

I'm in the middle of working on a program. I created a JFrame with a bunch of panels, buttons, labels and textfields that are supposed to be inside it. For some reason the JFrame apears, but with nothing inside it. Here's the code:

import javax.swing.*;
import java.awt.*;
import java.awt.Event.*;

public class GUI extends JFrame {

    JButton rect,oval,tri,free,addPoint;
    JLabel xLabel,yLabel;
    JTextField xTextField,yTextField;
    JPanel leftPanel,rightPanel,optionsPanel,pointsPanel;

    public GUI(){
        initUI();
    }

    private void initUI(){

        setLayout(new GridLayout(1,2,5,5));
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setTitle("Graphics Generator");
        setSize(500,500);
        setVisible(true);

        add(leftPanel);
        add(rightPanel);

        leftPanel.setLayout(new GridLayout(2,1,5,5));
        leftPanel.add(optionsPanel);

        optionsPanel.setLayout(new GridLayout(1,4,2,2));

        rect = new JButton("Rectangle");
        oval = new JButton("Oval");
        tri = new JButton("Triangle");
        free = new JButton("Free Shape");

        optionsPanel.add(rect);
        optionsPanel.add(oval);
        optionsPanel.add(tri);
        optionsPanel.add(free);

        leftPanel.add(pointsPanel);

        pointsPanel.setLayout(new GridLayout(1,5,2,2));

        pointsPanel.add(xLabel);
        pointsPanel.add(xTextField);
        pointsPanel.add(yLabel);
        pointsPanel.add(yTextField);
        pointsPanel.add(addPoint);

    }

    public static void main(String[] args) {

        GUI gui = new GUI();

    }

}

Upvotes: 0

Views: 83

Answers (3)

Paul Samsotha
Paul Samsotha

Reputation: 208944

None of your panels, textfields, or labels have been initialized. I'm getting NullPointerException

The code below will get your program running. But you really need to look into some LayoutManagers

private void initUI(){
    leftPanel = new JPanel();
    rightPanel = new JPanel();
    optionsPanel = new JPanel();
    pointsPanel = new JPanel();

    yLabel = new JLabel();
    xLabel = new JLabel();

    xTextField = new JTextField();
    yTextField = new JTextField();

    add(leftPanel);
    add(rightPanel);

    leftPanel.setLayout(new GridLayout(2,1,5,5));
    leftPanel.add(optionsPanel);

    optionsPanel.setLayout(new GridLayout(1,4,2,2));

    rect = new JButton("Rectangle");
    oval = new JButton("Oval");
    tri = new JButton("Triangle");
    free = new JButton("Free Shape");
    addPoint = new JButton("Add Point");

    optionsPanel.add(rect);
    optionsPanel.add(oval);
    optionsPanel.add(tri);
    optionsPanel.add(free);

    leftPanel.add(pointsPanel);

    pointsPanel.setLayout(new GridLayout(1,5,2,2));

    pointsPanel.add(xLabel);
    pointsPanel.add(xTextField);
    pointsPanel.add(yLabel);
    pointsPanel.add(yTextField);
    pointsPanel.add(addPoint);

    setLayout(new GridLayout(1,2,5,5));
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    setTitle("Graphics Generator");
    setSize(500,500);
    setVisible(true);

}

Upvotes: 1

mKorbel
mKorbel

Reputation: 109815

  • your JComponents aren't initialized,

  • you added JComponents to already visible JFrame,

  • you have to move code line setVisible(true); to the end of constructor,

  • Swing GUI should be crated on Initial Thread

Upvotes: 5

PakkuDon
PakkuDon

Reputation: 1615

You should invoke setVisible(true) after you're done adding your components. They won't render otherwise until there's a call to revalidate();

You also need to initialise your components before trying to use them.

Example:

leftPanel = new JPanel();
rightPanel = new JPanel();
add(leftPanel);
add(rightPanel);

Repeat for the other components.

Upvotes: 1

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