How can I switch between jpanels?

Question

I'm still very new to java programming, so please help me to correct any mistakes I might have overlooked or give tips on how to improve this program.

Okay, so a lot of problems have been solved, and now I have a CardLayout, but I still have questions about how I should make my pipes show inside it.

When I tried to add in my refresh rate timer and my speed timer, I have problems about how I need to declare and initialize boolean variables.

Also, when I compile and run this game, I get files such as Game$1.class. Is there a way for me to clean this up, and could someone explain why this happens? Do these have an affect on the finished product? (When the game is compiled and packaged into a JAR.)

I want to set playerIsReady to true when the play button is clicked. And from there, when the if statement is true, then switch to a panel that displays the pipes, and start moving the pipe across the screen. Preferably 3 instances of that pipe, each starting at different times, but whatever you can help with is fine.

Some of this code needs work, so I have commented some parts out and left notes.

My other questions about this game can be found here.

This is my current code

Game.java

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.border.EmptyBorder;
import javax.swing.SwingUtilities;

public class Game {

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {             
                // the GUI as seen by the user (without frame)
                final CardLayout cl = new CardLayout();
                final JPanel gui = new JPanel(cl);
                // remove if no border is needed
                gui.setBorder(new EmptyBorder(10,10,10,10));

                JPanel menu = new JPanel(new GridBagLayout());
                JButton playGame = new JButton("Play!");
                ActionListener playGameListener = new ActionListener() {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        cl.show(gui, "game");
                    }
                };
                playGame.addActionListener(playGameListener);
                Insets margin = new Insets(20, 50, 20, 50);
                playGame.setMargin(margin);
                menu.add(playGame);
                gui.add(menu);
                cl.addLayoutComponent(menu, "menu");

                final JPanel pipes = new Pipes();
                gui.add(pipes);
                cl.addLayoutComponent(pipes, "game");

                JFrame f = new JFrame("Pipes Game");
                f.add(gui);
                // Ensures JVM closes after frame(s) closed and
                // all non-daemon threads are finished
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                // See https://stackoverflow.com/a/7143398/418556 for demo.
                f.setLocationByPlatform(true);

                // ensures the frame is the minimum size it needs to be
                // in order display the components within it
                f.pack();
                // should be done last, to avoid flickering, moving,
                // resizing artifacts.
                f.setVisible(true);

                /*if (playerIsReady) { 
                    Timer speed = new Timer(10, new ActionListener() {  //pipe speed
                        @Override
                        public void actionPerformed(ActionEvent e) {
                            pipes.move();
                        }
                    });
                    speed.start();

                    Timer refresh = new Timer(30, new ActionListener() {    //refresh rate
                        @Override
                        public void actionPerformed(ActionEvent e) {
                            pipes.repaint();
                        }
                    });
                    refresh.start();
                }*/
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}

Pipes.java

// What import(s) do I need for ArrayList?
public class Pipes {
    List<Pipe> pipes = new ArrayList<Pipe>();

    public Pipes() {
        pipes.add(new Pipe(50, 100));
        pipes.add(new Pipe(150, 100));
        pipes.add(new Pipe(250, 100));
    }

    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        for ( Pipe pipe : pipes ){
            pipe.drawPipe(g);
        }
    }
}

PipeObject.java

import java.awt.Graphics;

public class PipeObject {
    //Declare and initialiaze variables
    int x1 = 754;               //xVal start
    int x2 = 75;                //pipe width
                                //total width is 83
    int y1 = -1;                //yVal start
    int y2 = setHeightVal();    //pipe height
    int gap = 130;              //gap height

    public void drawPipe(Graphics g) {

        g.clearRect(0,0,750,500);                       //Clear screen
        g.drawRect(x1,y1,x2,y2);                        //Draw part 1
        g.drawRect(x1-3,y2-1,x2+6,25);                  //Draw part 2
        g.drawRect(x1-3,y2+25+gap,x2+6,25);             //Draw part 3
        g.drawRect(x1,y2+25+gap+25,x2,500-y2-49-gap);   //Draw part 4
    }

    public void move() {
        x1--;
    }

    public int getMyX() {   //To determine where the pipe is horizontally
        return x1-3;
    }

    public int getMyY() {   //To determine where the pipe is vertically
        return y2+25;
    }

    public int setHeightVal() {     //Get a random number and select a preset height
        int num = (int)(9*Math.random() + 1);
        int val = 0;
        if (num == 9)
        {
            val = 295;
        }
        else if (num == 8)
        {
            val = 246;
        }
        else if (num == 7)
        {
            val = 216;
        }
        else if (num == 6)
        {
            val = 185;
        }
        else if (num == 5)
        {
            val = 156;
        }
        else if (num == 4)
        {
            val = 125;
        }
        else if (num == 3)
        {
            val = 96;
        }
        else if (num == 2)
        {
            val = 66;
        }
        else
        {
            val = 25;
        }
        return val;
    }
}

Answer 1

The best way to approach this is using a CardLayout.

Notes

• A button with an ActionListener is far better than a MouseListener over a rectangle.
  • The button will show focus when the mouse is pointed at it, or the component is tabbed to via the keyboard.
  • The button is keyboard accessible.
  • The button has facility to support multiple icons built in (e.g. for 'initial look', focused, pressed etc.)
• White space in the GUI is provided around the menu panel and game by adding an EmptyBorder
• The button is made larger by setting a margin.
• Adjust margins, borders and preferred size according to need. These sizes were set by me so as not to make the screenshots too large.
• See more tips in the code comments.

Code

Here is the MCTaRE (Minimal Complete Tested and Readable Example) that produced the above screenshots.

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.border.EmptyBorder;

public class PipesGame {

    public static void main(String[] args) {
        Runnable r = new Runnable() {
            @Override
            public void run() {
                // the GUI as seen by the user (without frame)
                final CardLayout cl = new CardLayout();
                final JPanel gui = new JPanel(cl);
                // remove if no border is needed
                gui.setBorder(new EmptyBorder(10,10,10,10));

                JPanel menu = new JPanel(new GridBagLayout());
                JButton playGame = new JButton("Play!");
                ActionListener playGameListener = new ActionListener() {

                    @Override
                    public void actionPerformed(ActionEvent e) {
                        cl.show(gui, "game");
                    }
                };
                playGame.addActionListener(playGameListener);
                Insets margin = new Insets(20, 50, 20, 50);
                playGame.setMargin(margin);
                menu.add(playGame);
                gui.add(menu);
                cl.addLayoutComponent(menu, "menu");

                JPanel pipes = new Pipes();
                gui.add(pipes);
                cl.addLayoutComponent(pipes, "game");

                JFrame f = new JFrame("Pipes Game");
                f.add(gui);
                // Ensures JVM closes after frame(s) closed and
                // all non-daemon threads are finished
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                // See https://stackoverflow.com/a/7143398/418556 for demo.
                f.setLocationByPlatform(true);

                // ensures the frame is the minimum size it needs to be
                // in order display the components within it
                f.pack();
                // should be done last, to avoid flickering, moving,
                // resizing artifacts.
                f.setVisible(true);
            }
        };
        // Swing GUIs should be created and updated on the EDT
        // http://docs.oracle.com/javase/tutorial/uiswing/concurrency
        SwingUtilities.invokeLater(r);
    }
}

class Pipes extends JPanel {

    Pipes() {
        setBackground(Color.BLACK);
        setForeground(Color.WHITE);
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawString("Pipes game appears here..", 170, 80);
    }

    @Override 
    public Dimension getPreferredSize() {
        // adjust to need
        return new Dimension(500,150);
    }
}

Answer 2

"Is there a way for me to add my GameMenu jpanel to my jframe, and then replace it with the Pipes jpanel?"

As other have suggested, for this you want a CardLayout. It is very simple to you. Personally, I always wrap my CardLayout in a JPanel rather than the JFrame, just force of habit.

What you want to do is have a mainPanel that will have the CardLayout

CardLayout card = new CardLayout();
JPanel mainPanel = new JPanel();

Then you want to add your panels to the mainPanel. What the CardLyaout does is layer the panels, making just one visible at a time. The first one you add, will the in the foreground. Also when you add the panel, you'll also want to issue it a key it can be called from. The key, can be any String you like.

mainPanel.add(gameMenu, "menu");
mainPnael.add(pipes, "pipe");

Now gameMenu is the only panel shown. To show pipes, all you do is use this method

• public void show(Container parent, String name) - Flips to the parent that was added to this layout with the specified name, using addLayoutComponent. If no such component exists, then nothing happens.

So you'd use, card.show(mainPanel, "pipes");

Whatever even you want to trigger the showing of pipes, just add that line in that event handler. You could add a button or something to the GameMenu that will allow movement to the Pipes panel.