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paint() doesn't work after panel and frame was added

I am making kind of my paint that creates shapes, it worked fine until I added layers(panel and frame), now the shapes aren't visible on button press I assume it is under the layers?i tried using paintComponent and revalidate etc and still couldn't get it to appear
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Main2 extends JPanel implements ActionListener {
private static Square mySquare;
private static Circle myCircle;
private static Color myColor;
public boolean SquareCheck;
public boolean CircleCheck;
JButton buttonSquare;
JButton buttonCircle;
JFrame frame;
JPanel panel;
public void paint(Graphics g) {
if (SquareCheck) {
g.setColor(myColor);
g.fillRect(mySquare.x, mySquare.y, mySquare.width, mySquare.length);
} else if (CircleCheck) {
g.setColor(myColor);
g.fillOval(myCircle.x, myCircle.y, myCircle.width, myCircle.length);
}
}
public void start() {
frame = new JFrame();
panel = new JPanel();
//setLayout(new BorderLayout());
buttonSquare = new JButton("■");
buttonCircle = new JButton("●");
buttonSquare.setPreferredSize(new Dimension(200, 20));
buttonCircle.setPreferredSize(new Dimension(200, 20));
buttonCircle.addActionListener(this);
buttonSquare.addActionListener(this);
//add(buttonCircle, BorderLayout.NORTH);
//add(buttonSquare, BorderLayout.SOUTH);
JToggleButton red = new JToggleButton();
panel.add(buttonCircle);
panel.add(buttonSquare);
frame.add(panel);
frame.setSize(500, 500);
frame.setVisible(true);
}
public void actionPerformed(ActionEvent e) {
if (e.getSource() == buttonSquare) {
SquareCheck = true;
} else if (e.getSource() == buttonCircle) {
CircleCheck = true;
}
repaint();
}
public static void main(String[] args) {
mySquare = new Square(30, 50, 50, 50);
myCircle = new Circle(60, 100, 50, 50);
myColor = Color.red;
Main2 x = new Main2();
x.start();
}
}
Basiclly the buttons changes the boolean then the repaint is called and based on the boolean it draws either a cirlce or a square,the code worked before adding frame and panel

Your paint method is a method of the Main2 class, but you never add a Main2 instance to the JFrame or to any component that goes into the JFrame, and so the Main2 instance will never be displayed, and the Swing painting manager will never call its paint method.
For starters, get rid of this variable, panel = new JPanel(); and every place you use panel, substitute this. This way you'll be working with a correct Main2 instance and adding it to the GUI.
Other issues:
You need to call the super's equivalent painting method in your override on its first line
Override paintComponent, not paint, and yes call super.paintComponenet(g); in this override
You will want to learn and use Java naming conventions. Variable names should all begin with a lower letter while class names with an upper case letter. Learning this and following this will allow us to better understand your code, and would allow you to better understand the code of others.
For safety's sake, add the #Override annotation above any method that you think may be overriding a parent method (such as paint), to make sure that you are doing it correctly.
For example:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
#SuppressWarnings("serial")
public class Main2 extends JPanel implements ActionListener {
private static Square mySquare;
private static Circle myCircle;
private static Color myColor;
private JToggleButton buttonSquare;
private JToggleButton buttonCircle;
JFrame frame;
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
if (buttonSquare.isSelected()) {
g.setColor(myColor);
g.fillRect(mySquare.x, mySquare.y, mySquare.width, mySquare.length);
}
if (buttonCircle.isSelected()) {
g.setColor(myColor);
g.fillOval(myCircle.x, myCircle.y, myCircle.width, myCircle.length);
}
}
public Main2() {
frame = new JFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
buttonSquare = new JToggleButton("■");
buttonCircle = new JToggleButton("●");
buttonCircle.addActionListener(this);
buttonSquare.addActionListener(this);
this.add(buttonCircle);
this.add(buttonSquare);
frame.add(this);
frame.setSize(500, 500);
frame.setVisible(true);
}
public void actionPerformed(ActionEvent e) {
repaint();
}
public static void main(String[] args) {
mySquare = new Square(30, 50, 50, 50);
myCircle = new Circle(60, 100, 50, 50);
myColor = Color.red;
new Main2();
}
}
class MyShape {
public int x, y, width, length;
public MyShape(int x, int y, int width, int length) {
this.x = x;
this.y = y;
this.width = width;
this.length = length;
}
}

How do I draw on a JPanel from multiple outside classes?

I am currently making a game with a main menu and a world where you actually play.
I have a class called Game, which inherits from JPanel and implements the Runnable, MouseListener, KeyListener and ActionListener interfaces
(only important parts included)
I also have two classes InWorldHandler and OutWorldHandler for handling the mechanics in the world and outside of it respectively.
The Game class:
public class Game extends JPanel implements Runnable, KeyListener, MouseListener, ActionListener
{
protected JFrame frame;
private Timer timer = new Timer(25, this);
private World world;
private Player player = new Player();
private boolean draw;
Game(World world)
{
frame = new JFrame("Minecraft 2D");
this.world = world;
player.enterWorld(world, this);
}
#Override
protected void paintComponent(Graphics g)
{
Graphics2D g2d = (Graphics2D)g;
if(draw)
{
g2d.setColor(new Color(255, 255, 255));
g2d.fillRect(0, 0, frame.getWidth(), frame.getHeight());
draw = false;
//Here, the in-game mechanics should be handled
if(player.inWorld())
{
Chunk chunk = player.getLoadedChunk();
for(int x = 0; x < 16; x++)
{
for(int y = 0; y < 16; y++)
{
Block block = chunk.getBlockAt(x, y);
BufferedImage texture = block.getTexture();
g2d.drawImage(block.getTexture(), x*32, y*32, texture.getWidth()*2, texture.getHeight()*2, null);
}
}
}
//Here, the out-game mechanics should be handled
else
{
}
}
}
#Override
public void actionPerformed(ActionEvent e)
{
this.repaint();
draw = true;
}
#Override
public void run()
{
draw = true;
frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
frame.add(this);
frame.setMinimumSize(new Dimension(518, 540));
frame.setResizable(false);
frame.setLocationRelativeTo(null);
frame.addKeyListener(this);
frame.addMouseListener(this);
frame.setFocusable(true);
frame.setVisible(true);
frame.pack();
timer.start();
}
}
Both the other classes have empty bodies currently. I just have no idea how to do that.
I want the InWorldHandler class to draw on the panel when the player is in game, and the OutWorldHandler class when the player is in the main menu, both called in the Game class. How do I do that?

Instead of having a single JPanel, why don't you try with a CardLayout and switch whether to show the InnerWorld or the OuterWorld according to a flag that determines where in the program you're at.
As you're implementing KeyListener, I think that's for you to be able to move your character, please take a look at the accepted answer on this question: Keylistener not working for JPanel and use KeyBindings instead.
Also avoid the use of setMimimum/Maximum/PreferredSize() and override those methods instead: Should I avoid the use of set(Preferred|Maximum|Minimum)Size methods in Java Swing?
Take this code as an example:
import java.awt.BorderLayout;
import java.awt.CardLayout;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
public class Game {
private JFrame frame;
private JButton button;
private boolean status;
private JPanel[] cards;
private CardLayout cl;
private JPanel gamePane;
public static void main(String[] args) {
SwingUtilities.invokeLater(() -> new Game().createAndShowGUI());
}
private void createAndShowGUI() {
frame = new JFrame(getClass().getSimpleName());
button = new JButton("Switch Worlds");
status = true; //True = Inner / False = Outer
cl = new CardLayout();
gamePane = new JPanel(cl);
cards = new JPanel[2];
cards[0] = new InnerWorld();
cards[1] = new OuterWorld();
gamePane.add(cards[0], "innerWorld");
gamePane.add(cards[1], "outerWorld");
button.addActionListener(e -> {
status = !status;
if (status) {
cl.show(gamePane, "innerWorld");
} else {
cl.show(gamePane, "outerWorld");
}
});
frame.add(gamePane);
frame.add(button, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
#SuppressWarnings("serial")
class InnerWorld extends JPanel {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.drawString("Inner World", 50, 50);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
#SuppressWarnings("serial")
class OuterWorld extends JPanel {
#Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D g2d = (Graphics2D) g;
g2d.drawString("Outer World", 50, 50);
}
#Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}

Java Drawing to a JPanel (debugging)

I'm trying to draw a basic object to a JPanel
although it doesn't seem to be working.
I'm certain I am doing something wrong with where the paint method
is being called
import javax.swing.*;
import java.awt.*;
import java.awt.image.*;
public class testGui {
static colors gc_colors;
static gui gc_gui;
public static void main(String[] args) {
gc_colors = new colors();
gc_gui = new gui();
gc_gui.cv_frame.setVisible(true);
}
public static class colors {
Color cv_ltGrey;
Color cv_mdGrey;
Color cv_dkGrey;
public colors() {
cv_ltGrey = Color.decode("#DDDDDD");
cv_mdGrey = Color.decode("#CCCCCC");
cv_dkGrey = Color.decode("#111111");
}
}
public static class gui {
JFrame cv_frame;
JPanel cv_panel;
JPanel cv_content;
public gui() {
cv_frame = new JFrame();
cv_frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cv_frame.setTitle("Test GUI");
cv_frame.setSize(600, 400);
cv_frame.setLayout(new FlowLayout());
cv_panel = new JPanel();
cv_panel.setBackground(gc_colors.cv_ltGrey);
cv_panel.setPreferredSize(new Dimension(500, 300));
cv_frame.add(cv_panel);
cv_content = new content();
cv_panel.add(cv_content);
}
}
public static class content extends JPanel {
public void paint(Graphics graphic) {
super.paint(graphic);
draw(graphic);
}
public void update() {
repaint();
}
public void draw(Graphics graphic) {
Graphics2D graphic2D = (Graphics2D) graphic;
graphic2D.setPaint(gc_colors.cv_ltGrey);
graphic2D.fillRect(10, 10, 100, 100);
}
}
}
I have a class for my gui which I am adding a JPanel to (a light grey one).
Which I am then trying to add my drawing to using a JPanel extended class
called content.
When I run it though it seems to create the grey JPanel which I want but
the drawing is just a tiny white square and I'm not sure why.

So, you content panel has a default preferred size of 0x0, FlowLayout honours the preferredSize of its components (with a little margin), hence the reason why you have a nice little small white rectangle.
What you need to do is override the getPreferredSize method of the content panel and return a suitable size, for example
public static class content extends JPanel {
#Override
public Dimension getPreferredSize() {
return new Dimension(120, 120);
}
public void paint(Graphics graphic) {
super.paint(graphic);
draw(graphic);
}
public void update() {
repaint();
}
public void draw(Graphics graphic) {
Graphics2D graphic2D = (Graphics2D) graphic;
graphic2D.setPaint(gc_colors.cv_ltGrey);
graphic2D.fillRect(10, 10, 100, 100);
}
}

I've decided to just leave out the second JPanel altogether.
It was too much of a hassle to put the JPanel inside of another JPanel
so instead I am only going to use a single JPanel
public static class gui {
JFrame cv_frame;
JPanel cv_panel;
JPanel cv_content;
public gui() {
cv_frame = new JFrame();
cv_frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
cv_frame.setTitle("Test GUI");
cv_frame.setSize(600, 400);
cv_frame.setLayout(new FlowLayout());
cv_content = new content();
cv_content.setBackground(gc_colors.cv_ltGrey);
cv_content.setPreferredSize(new Dimension(500, 300));
cv_frame.add(cv_content);
}
}

Trying to display Circles moving down but cannot remove circles drawn before

I am trying to make the effect of gravity but it just looks like there are growing streaks of circles instead of individual circles moving down. I do not know how to remove the circles I have already drawn. There are no errors in the code btw.
import javax.swing.Timer;
import javax.swing.*;
import java.awt.*;
import java.util.*;
import java.awt.event.*;
import java.awt.geom.Ellipse2D;
public class Tester {
static JFrame frame;
static JPanel panel;
static JButton button;
static ArrayList<Ellipse2D.Double> circles = new ArrayList<Ellipse2D.Double>();
static void init(){
frame = new JFrame();
panel = new JPanel(new BorderLayout());
button = new JButton("South");
panel.add(button, BorderLayout.SOUTH);
frame.add(panel);
frame.setVisible(true);
panel.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(500, 500);
frame.setBackground(Color.LIGHT_GRAY);
}
public static void main(String[] args) {
init();
class MeteorMover extends JPanel{
Ellipse2D.Double m;
int x = 40,y=40;
boolean isSettingGravity=true;
public MeteorMover(){
m = new Ellipse2D.Double(x,y,30,30);
}
void createNewMeteor(int n){
repaint();
}
void setGravity(){
isSettingGravity = true;
for (int i=0;i<circles.size();i++){
Ellipse2D.Double m = circles.get(i);
m= new Ellipse2D.Double(m.getX(),m.getY()+1,30,30);
circles.set(i, m);
}
repaint();
}
protected void paintComponent(Graphics g){
Graphics2D g2 = (Graphics2D) g;
g2.setColor(Color.WHITE);
if (isSettingGravity){
for (Ellipse2D.Double c:circles){
g2.draw(c);
}
isSettingGravity = false;
}
else{
m = new Ellipse2D.Double(x,y,30,30);
circles.add(m);
g2.fill(m);
g2.draw(m);
Random r = new Random();
x = r.nextInt(500);
y=r.nextInt(100);
}
}
}
final MeteorMover m = new MeteorMover();
panel.add(m);
panel.repaint();
class TimerListener implements ActionListener{
#Override
public void actionPerformed(ActionEvent arg0) {
m.createNewMeteor(1);
}
}
TimerListener cListener = new TimerListener();
Timer timer = new Timer(1000,cListener);
timer.start();
class TimerListener2 implements ActionListener{
#Override
public void actionPerformed(ActionEvent arg0) {
m.setGravity();
}
}
TimerListener2 gListener = new TimerListener2();
Timer gTimer = new Timer(100,gListener);
gTimer.start();
}
}

call super.paintComponent(g);
protected void paintComponent(Graphics g) {
super.paintComponent(g);
read more about super.paintComponent .

There's no direct way to erase with graphics, you have two options:
If you always know which ellipse you need to erase, AND the ellipses never intersect, then you could keep in memory which is the next ellipse to erase and call g.setColor(bgColor); g.fill(erasedEllipse);
This is option is more reliable, You could keep an ArrayList of ellipses to draw. and you could clear all the pane and repaint all
the ellipses in the ArrayList, and if you want to erase one, you
just call ArrayList.remove(erasedElipseIndex)

Java color changing Graphics with Timer

I want to draw a disc that changes colors twice a second. The disk is drawn on a DrawPanel which extends a JPanel and in the main method the DrawPanel is added to a frame.
For the colorchanging I use a timer which works when I'm trying to change the background of the DrawPanel in the main method (what i commented out).
Can someone tell me why it doesn't work for the Graphics g object or any other suggestions?
I just copied the code from the main method and added it into the paintComponent() method, but here it doesn't work.
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
public class DrawPanel extends JPanel{
public GridBagLayout gbl;
//position and dimension
int x = 0, y = 0, width = 200, height = 200;
public DrawPanel(){
repaint();
}
public DrawPanel(GridBagLayout gridBagLayout) {
this.gbl = gridBagLayout;
}
public void paintComponent(Graphics g){
//Overwriting of old picture
super.paintComponent(g);
ActionListener action = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
Random gen = new Random();
Color color = new Color(gen.nextInt(256), gen.nextInt(256), gen.nextInt(256));
//Draw color disk
g.setColor(color);
g.fillArc(x, y, width, height, 0, 360);
}
};
Timer t = new Timer(500, action);
t.setRepeats(true);
t.setInitialDelay(0);
t.start();
//Draw boundary of circle
g.setColor(Color.BLACK);
g.drawArc(x, y, width, height, 0, 360);
}
public static void main(String[] args) {
final JFrame frame = new JFrame();
frame.setSize(300, 300);
final DrawPanel panel = new DrawPanel();
panel.setOpaque(true);
frame.getContentPane().add(panel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
// ActionListener action = new ActionListener() {
// #Override
// public void actionPerformed(ActionEvent e) {
// Random gen = new Random();
// Color color = new Color(gen.nextInt(256), gen.nextInt(256), gen.nextInt(256));
// panel.setBackground(color);
// }
// };
//
// Timer t = new Timer(500, action);
// t.setRepeats(true);
// t.setInitialDelay(0);
// t.start();
}
}

The Graphics object is transient, so you should not cache it even if the compiler allows that. Instead establish the timer in the constructor of the class, set the BG of the panel, then call for a repaint. E.G.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Random;
public class DrawPanel extends JPanel {
Random gen = new Random();
//position and dimension
int x = 0, y = 0, width = 200, height = 200;
Color drawColor = Color.BLACK;
public DrawPanel() {
repaint();
ActionListener action = new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
Color color = new Color(gen.nextInt(256), gen.nextInt(256), gen.nextInt(256));
//Draw color disk
drawColor = color;
DrawPanel.this.repaint();
}
};
Timer t = new Timer(500, action);
t.setRepeats(true);
t.setInitialDelay(0);
t.start();
}
#Override
public void paintComponent(Graphics g) {
//Overwriting of old picture
super.paintComponent(g);
//Draw boundary of circle
g.setColor(drawColor);
g.drawArc(x, y, width, height, 0, 360);
}
public static void main(String[] args) {
final JFrame frame = new JFrame();
frame.setSize(300, 300);
final DrawPanel panel = new DrawPanel();
panel.setOpaque(true);
frame.getContentPane().add(panel);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

Graphics objects are only valid for that one draw
It would be better to instead to tell the JPanel to change it's current color (with a variable) and then tell it to repaint
Add variable discColor to your JPanel
Change your drawing code to not use timers and instead make it simple, just draw the disc based off of discColor
With a timer, update the discColor variable and then call the panel's repaint() method