Thread: How to remove a brick (Java)

im a bit of a beginner at this to say the least. How would i go about doing this?

Thank you

ok i will try that. Thank you

Originally Posted by usherlad

Hi,

Im stuck on what i think maybe a simple problem but im not sure what im doing wrong.

My assignment is for a ball to move by the click of a button round the page and if it hits the brick, remove the brick and add 10 to the score. I've managed to do it all except when my ball hits one side of the brick it adds 10 to the score and when it hits the other side of the brick it adds another 10. How do i get it so that when it hits the brick it only adds 10 no matter how often it hits where the brick is/was. I know its the way i have done the coding but i dont no how else to do it and was wondering if someone get help me or point me in the right direction please.

public void moveBall()
 
	{
 
		Graphics myPen = paper.getGraphics();
		myPen.setColor(Color.black);
		myPen.fillOval(x, y, diameter, diameter);
 
		x = x + xChange;
		y = y + yChange;
 
		if(x <= 0)
			xChange = -xChange;
		if(y <= 0)
			yChange = -yChange;
		if(x >= paper.getWidth())
			xChange = -xChange;
		if(y >= paper.getHeight())
			yChange = -yChange;
 
		myPen.setColor(Color.white);
		myPen.fillOval(x, y, diameter, diameter);
 
 
 
		if((y==100 && x == 80) || (y==110 && x == 80))
			removeRectangle();	
		if((y==100 && x == 85) || (y==110 && x == 85))
			removeRectangle();
		if((y==100 && x == 90) || (y==110 && x == 90))
			removeRectangle();
		if((y==100 && x == 95) || (y==110 && x == 95))
			removeRectangle();		
		if((y==100 && x == 100) || (y==110 && x == 100))
			removeRectangle();		
		if((y==100 && x == 105) || (y==110 && x == 105))
			removeRectangle();		
		if((y==100 && x == 110) || (y==110 && x == 110))
			removeRectangle();	
 
		if((y==102 && x == 80) || (y==102 && x == 110))
			removeRectangle();		
		if((y==104 && x == 80) || (y==104 && x == 110))
			removeRectangle();		
		if((y==106 && x == 80) || (y==106 && x == 110))
			removeRectangle();		
		if((y==108 && x == 80) || (y==108 && x == 110))
			removeRectangle();
 
 
public void drawRectangle()
	{
 
	int x1, y1, width, height, col1, col2, col3;	
	Graphics myPen1 = paper.getGraphics();
	myPen1.fillRect(80, 100, paper.getWidth(), paper.getHeight());
 
 
 
 
		col1 = random.nextInt(255);
		col2 = random.nextInt(255);
		col3 = random.nextInt(255);
 
 
		myPen1.setColor(new Color(col1, col2, col3));
 
		x1= 80;
		y1= 100;
		width = 30;
		height = 10;
		myPen1.drawRect(x1, y1, width, height);
	}
 
public void removeRectangle()
	{
		Graphics myPen1 = paper.getGraphics();
		myPen1.setColor(Color.black);
		myPen1.fillRect(x1, y1, paper.getWidth(),paper.getHeight());
 
 
		score = score+10;
		txtScore.setText(score + "");
 
	}

In 3 different methods you have the same line (except once the variable name is different:

Graphics myPen = paper.getGraphics();
Graphics myPen1 = paper.getGraphics();
Graphics myPen1 = paper.getGraphics();

This tells me you should have a higher level scope for just one variable and use it in all of the methods.

In your moveBall method it looks like you are keeping the values of x and y outside the method. I would suggest using an object rather than just two variables (a ball class perhaps). Then when your ball moves, you are drawing a new black ball over top of the old white ball. Then you check against the edges of your paper and draw a new white ball. This means that every time you move your ball, you actually draw 2 new ones. How long before you have hundreds of white ovals drawn under black ovals? thousands? run out of memory? By tracking just one ball object, you can actually move it, rather than drawing 2 new every moveBall call, and only ever have one ball drawn on the screen at a time.

In your moveBall method you check for hitting a brick by checking the location of the ball. Does this actually verify a brick is present? Or does it just verify the ball is in the position of a brick?

As far as your removeRectangle() method, changing the color of the brick to match the color of the background does not remove the object. Same problem the ball has with being redrawn. You never actually remove the brick, you just draw a black one over it. Now there are two bricks in that location. Here I would suggest the same solution as the ball. Perhaps a new brick class. Keep track of a group of bricks on the paper, and when a brick is hit, actually remove that brick object from the paper, don't hide it behind a new object.

Post all of your code if you have more questions so we can get a better idea of what is going on, and be more prepared to offer help. Sometimes a code snippet is enough, but sometimes it just helps to see the whole thing or a smaller version of the whole thing.

Hi, Sorry its taken ages for me to get back to you. I've been away.

I understand what your saying about drawing a black ball over a white ball and potentially running out of memory but thats the only way that i have been taught. I'm only using one brick so i shouldnt run out of memory.

In my moveBall method it verifys that the ball is in the position of the brick.

Im not sure how to remove the brick tho. I keep trying but i always end up where i started with a little bit more grey hair.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.Random;
 
public class BouncingBall1 extends JFrame implements ActionListener {
 
	private JPanel paper;
	private JButton btnGo, btnStop, btnFinish, btnLeft, btnRight, btnUp, btnDown;
	private int x, y, xChange, yChange, diameter;
	private int x1, y1;
	private Timer timer1;
	private JTextField txtScore;
	private JLabel lblScore;
	private int score;
	private Random random;
 
	public static void main(String[] args)
	{
 
		BouncingBall1 ball1 = new BouncingBall1();
		ball1.setSize(550, 550);
		ball1.setBackground(Color.GREEN);
		ball1.setVisible(true);
 
	}
 
	public BouncingBall1(){
		setLayout(new FlowLayout());	
 
		btnGo = new JButton("Start");
		btnGo.setPreferredSize(new Dimension (70,40));
		btnGo.setBackground(Color.gray);
 
		btnStop = new JButton("Stop");
		btnStop.setPreferredSize(new Dimension (70,40));
		btnStop.setBackground(Color.gray);
 
		btnFinish = new JButton("Finish");
		btnFinish.setPreferredSize(new Dimension (70,40));
		btnFinish.setBackground(Color.gray);
 
		btnLeft = new JButton("Left");
		btnLeft.setPreferredSize(new Dimension (70,40));
		btnLeft.setBackground(Color.gray);
 
		btnRight = new JButton("Right");
		btnRight.setPreferredSize(new Dimension (70,40));
		btnRight.setBackground(Color.gray);
 
		btnUp = new JButton("Up");
		btnUp.setPreferredSize(new Dimension (70,40));
		btnUp.setBackground(Color.gray);
 
		btnDown = new JButton("Down");
		btnDown.setPreferredSize(new Dimension (70,40));
		btnDown.setBackground(Color.gray);
 
		lblScore = new JLabel("Score");
		lblScore.setPreferredSize(new Dimension(50,40));
		lblScore.setBackground(Color.gray);
 
		txtScore = new JTextField(3);
		txtScore.setFont(new Font("TimesRoman", Font.BOLD,16));
		txtScore.setBackground(Color.white);
		txtScore.setForeground(Color.blue);
 
		paper = new JPanel();
		paper.setPreferredSize(new Dimension(500,400));
		paper.setBackground(Color.black);
 
 
 
		add(btnGo);
		add(lblScore);
		add(txtScore);
		add(btnStop);
		add(btnFinish);
		add(paper);
		add(btnLeft);
		add(btnRight);
		add(btnUp);
		add(btnDown);
 
		btnGo.addActionListener(this);
		btnStop.addActionListener(this);
		btnFinish.addActionListener(this);
		btnLeft.addActionListener(this);
		btnRight.addActionListener(this);
		btnUp.addActionListener(this);
		btnDown.addActionListener(this);
 
		random = new Random();
 
		x=10; y=10; xChange = 10; yChange = 0; diameter = 10;
 
	}
 
	public void moveBall()
 
	{
 
		Graphics myPen = paper.getGraphics();
		myPen.setColor(Color.black);
		myPen.fillOval(x, y, diameter, diameter);
 
		x = x + xChange;
		y = y + yChange;
 
		if(x <= 0)
			xChange = -xChange;
		if(y <= 0)
			yChange = -yChange;
		if(x >= paper.getWidth())
			xChange = -xChange;
		if(y >= paper.getHeight())
			yChange = -yChange;
 
		myPen.setColor(Color.white);
		myPen.fillOval(x, y, diameter, diameter);
 
 
		if((x>=80 && x<=110) && (y==110))
			removeRectangle();
 
 
 
	}
 
	public void drawRectangle()
	{
 
	int x1, y1, width, height, col1, col2, col3;	
	Graphics myPen1 = paper.getGraphics();
	myPen1.fillRect(80, 100, paper.getWidth(), paper.getHeight());
 
 
 
 
		col1 = random.nextInt(255);
		col2 = random.nextInt(255);
		col3 = random.nextInt(255);
 
 
		myPen1.setColor(new Color(col1, col2, col3));
 
		x1= 80;
		y1= 100;
		width = 30;
		height = 10;
		myPen1.drawRect(x1, y1, width, height);
	}
 
 
 
 
 
	public void removeRectangle()
	{
		Graphics myPen1 = paper.getGraphics();
		myPen1.setColor(Color.black);
		myPen1.fillRect(x1, y1, paper.getWidth(),paper.getHeight());
 
		Score();
 
	}
 
	public void Score()
 
	{
		score = score+10;
		txtScore.setText(score + "");
 
	}
 
 
 
 
 
	public void actionPerformed(ActionEvent event)
 
	{
		if(event.getSource()==btnGo)
 
		{
			timer1 = new Timer(50,this);
			timer1.start();
 
		}
 
		if(event.getSource()==timer1)
		{
			moveBall();
		}
 
		if(event.getSource()==btnStop)
		{
			timer1.stop();
 
		}
 
		if(event.getSource()==btnGo)
 
		{
			drawRectangle();
		}
 
 
		if(event.getSource()==btnFinish)
		{
			JOptionPane.showMessageDialog(null, "Thank You for Playing! You scored  " +score++);
			System.exit(0);
 
		}
 
		if(event.getSource()==btnLeft)
		{
			xChange = -10; yChange = 0;
		}
		if(event.getSource()==btnRight)
		{
			xChange = 10; yChange = 0;
		}
		if(event.getSource()==btnUp)
		{
			xChange = 0; yChange = -10;
		}
		if(event.getSource()==btnDown)
		{
			xChange = 0; yChange = 10;
		}
		moveBall();
	}
 
 
	}

yeah thats what it does and when the ball hits the rectangle it adds 10points to the score. Its very basic i know but its all i need to do. The problem with it is that i only want it to add 10points once and not everytime it passes through the space where the rectangle is. Thats the only thing im stuck on and once i've managed to sort that out i will have finished the program

Hope that makes sense

yeah i remember you saying that previously. Because im a beginner it all sounds double dutch unfortunately.

I understand about the hardcoded values but i didnt know what else to do.

I'm not asking you to do it for me at all but is there any way could point me abit more in the right direction please

Thank you

Originally Posted by Norm

Where are the variables defined that hold the state of a brick?

they're held in drawRectangle.

been tryiing to do this all night but not getting anywhere.

This may sound stupid but what are the public voids called. Are they called subclasses? can you link a boolean expression between them?

how do you write the code not to change the score? i have never been taught that

i know this isnt the correct way to do it but so far i have got

 public void moveBall()
 
	{
		boolean beenHit = false;	
		Graphics myPen = paper.getGraphics();
		myPen.setColor(Color.black);
		myPen.fillOval(x, y, diameter, diameter);
 
		x = x + xChange;
		y = y + yChange;
 
		if(x <= 0)
			xChange = -xChange;
		if(y <= 0)
			yChange = -yChange;
		if(x >= paper.getWidth())
			xChange = -xChange;
		if(y >= paper.getHeight())
			yChange = -yChange;
 
		myPen.setColor(Color.white);
		myPen.fillOval(x, y, diameter, diameter);
 
 
		if((x>=80 && x<=110) && (y==110) && (beenHit == false))
			removeRectangle();
 
	}

im trying to get the boolean in removeRectangle() set to true so that once the rectangle has been removed it wont try and remove the rectangle again therefore not adding the score again if that makes sense.

 public void removeRectangle()
	{
		boolean beenHit = true;
		Graphics myPen2 = paper.getGraphics();
		myPen2.setColor(Color.black);
		myPen2.fillRect(x1, y1, paper.getWidth(),paper.getHeight());
 
 
		Score();
 
	}

the code wont work and im not sure why.

so there is no way of linking the boolean in the moveBall method and the removeRectangle method?

sorry if all my questions are stupid but im just trying to find out.

is public static void main(String[] args) or public BouncingBall1(){ class level

can i link a boolean and method together. For example:

Boolen BeenHit = false

.........

if false
drawRectangle()

else
removeRectangle()

ignore what i previously. I have wrote this at class level.

 
if ((x>=x1 && x<=x2) && (y==y1) && beenHit == false){
				removeRectangle();
 
		}else{
 
			beenHit = true;

its so that once it has ran the removeRectangle method it wont run it again therefore not adding more than it should. At the moment its not even adding anything to the score

Originally Posted by usherlad

Hi, Sorry its taken ages for me to get back to you. I've been away.

I understand what your saying about drawing a black ball over a white ball and potentially running out of memory but thats the only way that i have been taught. I'm only using one brick so i shouldnt run out of memory.

Only using one brick, (for now) is not a good reason to continue down a rocky road.

Originally Posted by usherlad

In my moveBall method it verifys that the ball is in the position of the brick.

Correct. So even if the brick was gone rather than 'invisible-on-screen', your method will still signal that you hit a brick when the ball enters the location because that is what you test for.

Originally Posted by usherlad

Im not sure how to remove the brick tho. I keep trying but i always end up where i started with a little bit more grey hair.

Store your brick object in a variable so you have access to it. Then you can add/relocate/remove it with a method call. Same for the ball.