Thread: Java Program - Graphics - Ball Drop and Retrieve

I am trying to make a display window with three buttons, "Drop", "Retrieve", and "Quit". When "Drop" is clicked, a ball must drop from the top of the screen and stop at the bottom. When "Retrieve" is clicked, a line must ascend from the top of the screen to retrieve the ball, and bring the ball back to the top of the screen. "Quit" should do the obvious. I was given this to start with:

/**
 * A class that puts a graphics window on your display
 */
 
import java.awt.*;
import javax.swing.*;
 
public class DisplayWindow extends JFrame {
 /**
  * Content pane that will hold the added Jpanel
  */
 private Container c;
 
 /**
  * DisplayWindow constructor - no parameters
  */
 public DisplayWindow() {
  super("Display");
  c = this.getContentPane();
 }
 
 /**
  * Adds panel to content pane
  * 
  * @parameter the panel to be added
  */
 public void addPanel(JPanel p) {
  c.add(p);
 }
 
 /**
  * consolidates the frame, makes it visible, causes program termination when
  * window is closed manually
  */
 public void showFrame() {
  this.pack();
  this.setVisible(true);
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 }
}

public class DropDriver {
 
 public static void main(String[] args) {
  DisplayWindow d = new DisplayWindow();
  DropPanel b = new DropPanel();
  d.addPanel(b);
  d.showFrame();
 }
}

And I must create the DropPanel class. This is what I have so far:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
 
public class DropPanel extends JPanel implements ActionListener{
  int width = 300;
  int height = 600;
  Timer ticker = new Timer(20, this);
  int x = 0;
  int y = 0;
}
public Drop(){
  set preferred size(new Dimension (width,height));
  ticker.start();
}
public void paintComponent(Graphics g){
  super.paintComponent(g);
  g.drawOval(x,y,50);
}
public void actionPerformed(ActionEvent e){
  if(e.getSource() == ticker){
    y = y-2;
  }
  repaint();
  }
}

any suggestions on where to go from here? I'm having a hard time.

Well, right now my part of the program is pretty much all compilation errors. I have yet to even add the part where the ball is retrieved, nor have I added any buttons. I am mostly concerned with the ball dropping portion. I am getting the following errors:

9 errors found:
File: C:\Users\Edward\DropPanel.java [line: 12]
Error: C:\Users\Edward\DropPanel.java:12: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 14]
Error: C:\Users\Edward\DropPanel.java:14: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 15]
Error: C:\Users\Edward\DropPanel.java:15: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 16]
Error: C:\Users\Edward\DropPanel.java:16: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 18]
Error: C:\Users\Edward\DropPanel.java:18: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 19]
Error: C:\Users\Edward\DropPanel.java:19: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 20]
Error: C:\Users\Edward\DropPanel.java:20: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 23]
Error: C:\Users\Edward\DropPanel.java:23: class, interface, or enum expected
File: C:\Users\Edward\DropPanel.java [line: 25]
Error: C:\Users\Edward\DropPanel.java:25: class, interface, or enum expected

OK thanks! I've updated my code, an attempted to add some buttons...

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
 
 
public class DropPanel extends JPanel implements ActionListener{
 
  JButton drop = new JButton("Drop");
  JButton retrieve = new JButton("Retrieve");
  int width = 300;
  int height = 600;
  Timer ticker = new Timer(20, this);
  int x = 0;
  int y = 200;
 
public DropPanel(){
  setPreferredSize(new Dimension (width,height));
  this.add(drop);
  this.add(retrieve);
  drop.addActionListener(this);
  retrieve.addActionListener(this);
  ticker.start();
}
public void paintComponent(Graphics g){
  super.paintComponent(g);
  g.setColor(Color.green);
  g.fillOval(x,y,50,50);
}
public void actionPerformed(ActionEvent e){
  if(e.getSource() == ticker){
    y = y+2;
  }
  repaint();
  }
}

Everything compiles nicely, but when I try to run the program I get an error saying that there is no static void main method to accept the string. But I was pretty sure I didn't need a p.s.v.m.(s[]a) line in this program.

--- Update ---

There is a static void main method in the driver already

Yes there are three classes in total for this program:

/**
 * A class that puts a graphics window on your display
 */
 
import java.awt.*;
import javax.swing.*;
 
public class DisplayWindow extends JFrame {
 /**
  * Content pane that will hold the added Jpanel
  */
 private Container c;
 
 /**
  * DisplayWindow constructor - no parameters
  */
 public DisplayWindow() {
  super("Display");
  c = this.getContentPane();
 }
 
 /**
  * Adds panel to content pane
  * 
  * @parameter the panel to be added
  */
 public void addPanel(JPanel p) {
  c.add(p);
 }
 
 /**
  * consolidates the frame, makes it visible, causes program termination when
  * window is closed manually
  */
 public void showFrame() {
  this.pack();
  this.setVisible(true);
  this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 }
}

public class DropDriver {
 
 public static void main(String[] args) {
  DisplayWindow d = new DisplayWindow();
  DropPanel b = new DropPanel();
  d.addPanel(b);
  d.showFrame();
 }
}

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
 
 
public class DropPanel extends JPanel implements ActionListener{
 
  JButton drop = new JButton("Drop");
  JButton retrieve = new JButton("Retrieve");
  int width = 300;
  int height = 600;
  Timer ticker = new Timer(20, this);
  int x = 0;
  int y = 200;
 
public DropPanel(){
  setPreferredSize(new Dimension (width,height));
  this.add(drop);
  this.add(retrieve);
  drop.addActionListener(this);
  retrieve.addActionListener(this);
  ticker.start();
}
public void paintComponent(Graphics g){
  super.paintComponent(g);
  g.setColor(Color.green);
  g.fillOval(x,y,50,50);
}
public void actionPerformed(ActionEvent e){
  if(e.getSource() == ticker){
    y = y+2;
  }
  repaint();
  }
}

--- Update ---

The first two were given, the third is the one that I have created so far.

Omg exciting! I was running the DropPanel but was supposed to be running DropDriver. So, when I run DropDriver, A window pops up with my two buttons, and a green ball starts dropping from about the middle of the window before I even click a button. Then, it doesn't stop and rest on the button of the window like it should, but rather moves right off the page.

Changed some things. Now, when I run the program, the window pops up with two buttons and a green ball at the top of the screen. When I click "Drop", the ball only drops 20 pixels, but does not continue to drop. I am going to try and figure out how to get the timer to work.

--- Update ---

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
 
 
public class DropPanel extends JPanel implements ActionListener{
 
  JButton drop = new JButton("Drop");
  JButton retrieve = new JButton("Retrieve");
  int width = 300;
  int height = 600;
  Timer ticker = new Timer(20, this);
  int x = 0;
  int y = 0;
 
public DropPanel(){
  setPreferredSize(new Dimension (width,height));
  this.add(drop);
  drop.addActionListener(this);
  ticker.start();
  this.add(retrieve);
  retrieve.addActionListener(this);
  ticker.start();
}
public void paintComponent(Graphics g){
  super.paintComponent(g);
  g.setColor(Color.green);
  g.fillOval(x,y,50,50);
}
public void actionPerformed(ActionEvent e){
  if(e.getSource() == drop){
    y = y+2;
  }
  repaint();
  }
}

--- Update ---

I can't figure out how to implement a ticker so that when the buttons are clicked, that action happens. I think I need to use a boolean, but I don't know how.

--- Update ---

I have this much so far:

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
 
 
public class DropPanel extends JPanel implements ActionListener{
 
 private boolean clicked=true;
 
  JButton drop = new JButton("Drop");
  JButton retrieve = new JButton("Retrieve");
  int width = 300;
  int height = 600;
  private Timer ticker = new Timer(20, this);
  int x = 0;
  int y = 0;
 
public DropPanel(){
  setPreferredSize(new Dimension (width,height));
  this.add(drop);
  ticker.start();
  drop.addActionListener(this);
  this.add(retrieve);
  retrieve.addActionListener(this);
}
public void paintComponent(Graphics g){
  super.paintComponent(g);
  g.setColor(Color.green);
  g.fillOval(x,y,50,50);
  g.drawLine(25,y,25,0);
}
public void actionPerformed(ActionEvent e){
  if(e.getSource() == ticker){
    ticker.start();
    y += 2;
  }
  repaint();
  }
}

I updated my code to this and it still isn't doing what it's supposed to

import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
 
 
public class DropPanel extends JPanel implements ActionListener{
 
 private boolean clicked=true;
 
  JButton drop = new JButton("Drop");
  JButton retrieve = new JButton("Retrieve");
  JButton quit = new JButton("Quit");
  int width = 300;
  int height = 600;
  Timer ticker = new Timer(20, this);
  int x = 0;
  int y = 0;
  int z = 0;
 
public DropPanel(){
  setPreferredSize(new Dimension (width,height));
  this.add(drop);
  drop.addActionListener(this);
  this.add(retrieve);
  retrieve.addActionListener(this);
  this.add(quit);
  quit.addActionListener(this);
}
public void paintComponent(Graphics g){
  super.paintComponent(g);
  g.setColor(Color.green);
  g.fillOval(x,y,50,50);
  g.drawLine(25,z,25,0);
}
public void actionPerformed(ActionEvent e){
  if(e.getSource() == drop){
    ticker.start();
    y += 2;
    repaint();
  }
  if(e.getSource() == retrieve){
    ticker.start();
    z += 2;
  }
  }
}

I have already outlined earlier in this forum what my code is supposed to do. It is supposed to display a window with three buttons, "Drop", "Retrieve", and "Quit", and a ball. My code accomplished these things. However, when "Drop" is clicked, the ball is supposed to drop to the bottom of the window, and sit there. When I click my "Drop" button, however, the ball only moves down a tiny bit. It moves further with each click. When "Retrieve" is clicked, a string is supposed to drop down to the ball, and then the ball and the string are supposed to move back up to the top of the page, as if the string has descended to retrieve the ball. However, nothing happens when I click the "Retrieve" button. In an earlier version of my code, when I replaced the statement if(e.getSource == drop) with if(e.getSource == ticker) , I would run the program, and the both the ball and the string would drp to the bottom of the page and keep moving off the page, without me clicking any buttons at all.