Thread: Challenge: I need an animation loop outside of the paint method.

put the animation loop of my StarScape outside of the paint method so that my code does not cripple the system

To rewrite your StarScape program, take the do while loop out of the paint method. Just two lines with the do and the while, leave the contents of the loop.
Create a thread and put the do while loop in its run method. Inside the loop do a sleep of a short duration and a call to repaint. Done.
Also move the filling of the stars array outside of the paint method. Correct the constructor looking method to be a constructor and use it in the initialization loop.

how repaint() works. Does it just make the program go through the paint(Graphics g) each time it is called?

Yes, in most cases.

in a class outside of a method.

Most executed statements should be in a method. Statements that Initialize variables can be outside.

Then you need to put the code in a method.

Thank you. I will post back after some re-coding.

okay it sort of works. I have to keep resizing the window to see the animation. Is there a way to make it run on it's own without the need to resize the window to see the next frame?

here is the code:

New StarScape.java:

// starscape.java
// by Jon Crawford
import Star.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.geom.*;
import java.io.*;
import java.math.*;
 
public class StarScape extends JApplet 
{
  final int maxStars = 1000;
  String key = "";
  String valid;
  int index;
  double myX;
  double myY;
  int myRadius;
  double myLayer;
  int rectX;
  int rectY;
  int rectXX;
  int rectYY;
  Star stars[] = new Star[maxStars+1];//make 1000 star objects
 
  public void init()
  {
    for (index = 0; index < maxStars; index++)
    {
      myX = Math.random() * 200 - 99;//star starts in a small square
      myY = Math.random() * 200 - 99;//in the center
      myLayer = Math.random() * 3;//random layer
      stars[index] = new Star();//fill array with stars
    }//end for 
  }//end init
 
  public void paint(Graphics g)
  {
    g.setColor(Color.black);
    g.fillRect(0,0,800,600);// make the background black
    for (index = 0; index < maxStars; index++) 
    {
      stars[index].moveStar();//move the star
      stars[index].starValid();
      valid = stars[index].getValid();//is the star out of bounds?
      if (valid == "false")
      {//is star out of bounds?
        myX = Math.random() * 200 - 99;//set new starting position
        myY = Math.random() * 200 - 99;
        myLayer = Math.random() * 3;//new random layer
        stars[index].resetStar(myX, myY, myLayer);
      }  
      myX = stars[index].getStarX();
      myY = stars[index].getStarY();
      myRadius = stars[index].getStarRadius();//get data agian because star was moved
      myLayer = stars[index].getStarLayer();//layer just denotes shade of star. 
      if (myLayer == 3) 
      {
        g.setColor(Color.white);
      }else if (myLayer == 2) 
      {
        g.setColor(Color.lightGray);
      }else if (myLayer == 1) 
      {
        g.setColor(Color.darkGray);
      }else 
      {
        g.setColor(Color.white);//these set color based on layer
      }
      rectX = (int)(myX) - myRadius + 399;
      rectY = (int)(myY) - myRadius + 299;
      rectXX = myRadius * 2;
      rectYY = myRadius * 2;//set up the new star I mean rectangle
      g.fillOval(rectX, rectY, rectXX, rectYY);//draw star
    }//end for
  }//end paint
 
  public void doIt()
  {
    do
    {
      repaint();
    }while (key == "");
  }//end do it
}//end starscape

for the imported star.java please refer to: http://www.javaprogrammingforums.com...-day-12-a.html

unless they need a for loop.

public class StaticInitializerInside
{
  public final static String[] A_LOT_OF_STRINGS = new String[1000];
  static
  {
    int i = 0;
    for (String s : A_LOT_OF_STRINGS)
      A_LOT_OF_STRINGS[i++] = i + "!";
  }
}

You never call repaint() in your code. Repaint only 'requests' a paint, it doesn't force one. Resizing your window also requests a paint.

I thought
stars[index] = new Star();//fill array with stars
was calling the consrtuctor

how do I force a repaint?

Originally Posted by Norm

  stars[index] = new Star();//fill array with stars

Why don't you use the "constructor" method to fill in the values when the Star object is created?

Where is the Thread to run the loop creating the animation?
Who calls the doIt method?

Thought that was calling the constructor

I still have more reading to do on threads, I gotta go to work soon so I'm leaving that till tonight

lol doIt should be converted to a thread i guess.

It looks like it should work almost as is since when resizing the window the stars do move, I just need to force a repaint somehow.

Where is the code for the Star class's constructor?
There is a method in the class that looks like a constructor. Why not convert that to be a constructor and use it?
Make the variables that belong to the Star class private to that class vs having them global.
In your initialization loop you give values to 3 variables but those values are never used:

      myX = Math.random() * 200 - 99;//star starts in a small square
      myY = Math.random() * 200 - 99;//in the center
      myLayer = Math.random() * 3;//random layer
      stars[index] = new Star();//fill array with stars

Those variables should be passed to the Star class constructor.

how do I force a repaint?

By doing what you were doing the other day that crippled my PC. You really don't want to force a repaint. What you want to do is to time your requests to repaint at a nice rate that the windowing system can comply with. Anything else will work really, really badly. Norm is telling you all the right things, you just need to spend a bit more time re-reading and polishing up your code. You only really need a thread for this if you're going to be doing something else as well as animating the stars. If you're only going to be animating stars, you can just sleep the *current thread* - that's a clue as to which method in Thread you need to get access to it.

If it was a constructor it would say

public Star(/*whatever*/)

What you've posted there is a method called Star with a void return type.

public void Star(double myX, double myY, double myLayer)

That is not a constructor. Constructors do NOT have a void. This is the line of code I have mentioned in posts 2, 10 and 16.

Also look at this line, it doesn't pass any arguments:

 stars[index] = new Star();//fill array with stars

Originally Posted by Sean4u

What you've posted there is a method called Star with a void return type.

lol and yet it works. I did not want to become a hacker....

and when I remove the void it tells me I forget to add a return.

Is this because I forgot to put in a default constructor, and I just have the overloaded one?

when I remove the void it tells me I forget to add a return.

When you get errors that you don't understand, you need to post them instead of ignoring them.

complete code so far:

StarScape.java

// starscape.java
// by Jon Crawford
import Star.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.geom.*;
import java.io.*;
import java.math.*;
 
public class StarScape extends JApplet 
{
  final int maxStars = 1000;
  String key = "";
  String valid;
  int index;
  double myX;
  double myY;
  int myRadius;
  double myLayer;
  int rectX;
  int rectY;
  int rectXX;
  int rectYY;
  Star stars[] = new Star[maxStars+1];//make 1000 star objects
 
  public void init()
  {
    for (index = 0; index < maxStars; index++)
    {
      myX = Math.random() * 200 - 99;//star starts in a small square
      myY = Math.random() * 200 - 99;//in the center
      myLayer = Math.random() * 3;//random layer
      stars[index] = new Star();//fill array with stars
    }//end for 
  }//end init
 
  public void paint(Graphics g)
  {
    g.setColor(Color.black);
    g.fillRect(0,0,800,600);// make the background black
    for (index = 0; index < maxStars; index++) 
    {
      stars[index].moveStar();//move the star
      stars[index].starValid();
      valid = stars[index].getValid();//is the star out of bounds?
      if (valid == "false")
      {//is star out of bounds?
        myX = Math.random() * 200 - 99;//set new starting position
        myY = Math.random() * 200 - 99;
        myLayer = Math.random() * 3;//new random layer
        stars[index].resetStar(myX, myY, myLayer);
      }  
      myX = stars[index].getStarX();
      myY = stars[index].getStarY();
      myRadius = stars[index].getStarRadius();//get data agian because star was moved
      myLayer = stars[index].getStarLayer();//layer just denotes shade of star. 
      if (myLayer == 3) 
      {
        g.setColor(Color.white);
      }else if (myLayer == 2) 
      {
        g.setColor(Color.lightGray);
      }else if (myLayer == 1) 
      {
        g.setColor(Color.darkGray);
      }else 
      {
        g.setColor(Color.white);//these set color based on layer
      }
      rectX = (int)(myX) - myRadius + 399;
      rectY = (int)(myY) - myRadius + 299;
      rectXX = myRadius * 2;
      rectYY = myRadius * 2;//set up the new star I mean rectangle
      g.fillOval(rectX, rectY, rectXX, rectYY);//draw star
    }//end for
  }//end paint
 
  public void doIt()
  {
    do
    {
      repaint();
    }while (key == "");
  }//end do it
}//end starscape

Star.java

// star.java
// by Jon Crawford
package Star;
 
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.awt.geom.*;
import java.io.*;
import java.math.*;
 
public class Star {
 
  private final int starSpeed = 1;
  private final int starRadius = 1;
  private final int starSteps = 0;
  private final float[] invalidValues = new float[]{ -399f, -299f, 399f, 299f, 0f, 0f};
  private String isValid = "false";
  private double starAngle;
  private double starField[] = new double[9];
 
  public Star()
  {
    for (int num = 0;num < 9; num++)
    {
      starField[num] = 0;
    }// end for
  }//end consructor
 
  public Star(double myX, double myY, double myLayer)
  {
    starAngle = (Math.sqrt((myX * myX)+(myY * myY)));//calculate the hypotenuse
    starField[0] = myX;//set data to star's arrary
    starField[1] = myY;//this is for current position
    starField[2] = myX / starAngle * starSpeed;//these set the next position
    starField[3] = myY / starAngle * starSpeed;//this is reltive current position
    starField[4] = myLayer;//back, mid, or foreground layer
    starField[5] = starRadius;//star starting size
    starField[6] = starSpeed * myLayer;//the starting speed
    starField[7] = starSteps;//star has taken 0 steps, every 5 steps star grows and speeds up
    starField[8] = starAngle;//store the hypotenuse
  }//end constructor
 
  public void moveStar() 
  {//mutator method
    System.out.println("") ;    
    starField[0] = starField[0] + starField[2];//next position becomes the curent position 
    starField[1] = starField[1] + starField[3];       
    starField[2] = starField[0] / starField[8] * starField[6];//new next position
    starField[3] = starField[1] / starField[8] * starField[6];
    starField[7] = starField[7] + 1;//increment steps
    if (starField[7] / 5 == (int)(starField[7] / 5) && starField[5] < 20)
    {//if star has taken 5 steps
      starField[5] = starField[5] + 1;//increment size
      starField[6] = starField[6] + 1;//increment speed
    }//end if      
  }//end moveStar
 
  public void resetStar(double myX, double myY, double myLayer)
  {//resetStar method
    starAngle = (Math.sqrt((myX * myX)+(myY * myY)));//calculate new hypotenuse
    starField[0] = myX;//set data to star's array
    starField[1] = myY;//same as default constructor
    starField[2] = myX / starAngle * starSpeed;
    starField[3] = myY / starAngle * starSpeed;
    starField[4] = myLayer;
    starField[5] = starRadius;
    starField[6] = starSpeed * myLayer;
    starField[7] = starSteps;
    starField[8] = starAngle;
  }//end resetStar
 
  public void starValid()
  {//isValid method
    if(starField[0] > invalidValues[0] && starField[1] > invalidValues[1] && starField[0] < 
 
invalidValues[2] && starField[1] < invalidValues[3])
    {//in bounds?
      isValid = "true";
    }else
    {//out of bounds
      isValid = "false";
    }//end if
  }//end is valid
 
  public int getStarX() 
  {//get method
    return (int)(Math.round(starField[0]));
  }//end getStarX
 
  public int getStarY() 
  {//get method
    return (int)(Math.round(starField[1]));
  }//end getStarY
 
  public int getStarRadius() 
  {//get method
    return (int)(Math.round(starField[5]));
  }//end getStarRadius
 
  public int getStarLayer() 
  {//get method
    return (int)(Math.round(starField[4]));
  }//end getStarLayer
  public String getValid()
  {//get method
    return isValid;
  }//end isValid
 
}//end class star

later I'll work on threads, I hate that right now I have to resize the window constantly to see the animation

validate(); has the same result as repaint();