Array of colors in paintComponent method.

[Jonathan Haybok]

I can't seem to figure out how to fill the polygons I made with random colors. My assignment specifically says to generate 10 random colors, use an array to store the 10 colors and then use the colors to fill the ten polygons I made. Right now my array seems to just hold numbers between 0 and 255, and I don't know how I would set up the 10 RGB sets.

Lines 57 to 66 is where the specific code is.

 import javax.swing.JPanel;
import java.awt.*;
import java.util.Random;

public class GridPanel extends JPanel
{
   private int[] xX = new int[8];
   private int[] yX = new int[8];
	
	private int[] startX;
	private int[] startY;
   //-----------------------------------------------------------------
   //  Constructor: Sets up the basic characteristics of this panel.
   //-----------------------------------------------------------------
   public GridPanel(int[] startPointX, int[]startPointY)
   {
		//gathers arrays of start values
		startX = startPointX;
		startY = startPointY;
		
		//sets background and dimensions
      setBackground (Color.black);
      setPreferredSize (new Dimension(200, 200));
   }

   //-----------------------------------------------------------------
   //  Draws a rocket using polygons and polylines.
   //-----------------------------------------------------------------
   public void paintComponent (Graphics page)
   {
		//calls paintComponent method of JPanel parent class
      super.paintComponent (page);
		
		//loop to 
		for(int index = 0; index < 10; index++)
		{   
			//draws polygon using the start values  
		   xX[0] = startX[index];
			xX[1] = startX[index]+30;
			xX[2] = startX[index]+0;
			xX[3] = startX[index]+50;
			xX[4] = startX[index]+90;
			xX[5] = startX[index]+50;
			xX[6] = startX[index]+90;
			xX[7] = startX[index]+50;
		
		   yX[0] = startY[index];
			yX[1] = startY[index]+70;
			yX[2] = startY[index]+150;
			yX[3] = startY[index]+110;
			yX[4] = startY[index]+150;
			yX[5] = startY[index]+70;
			yX[6] = startY[index]+0;
			yX[7] = startY[index]+30;
			
		  
			int[] color = new int[9];
			//creates color object that will be random
         Random generator = new Random();
			for(int i = 0; i < 10; i++)
			{
				color[index] = generator.nextInt(256);
			
			page.setColor (color[index]);
    		page.fillPolygon (xX, yX, xX.length);
			}
		}

   }
}   

[Gregg Bolinger]

setColor expects a java.awt.Color object. What I might do is generate 3 random #'s 10 times. One for each: Red, Green, and Blue. I'd have a java.awt.Color[] and populate it with 10 Color objects.

for (int i = 0; i < 10; i++) {
   color[i] = new Color(randomR, randomB, randomG, 1.0f); // the 1.0f is the alpha
}

Then do your page.setColor(color[index]);

[Jonathan Haybok]

I wrote this out, and get this: "AWT-EventQueue-0" java.lang.IllegalArgumentException: Color parameter outside of expected range: Red Green Blue"

  for (int i=0; i<10; i++) 
			{ 
				int randomR = (int) (Math.random()*255);
         	int randomB = (int)(Math.random()*255);
         	int randomG = (int) (Math.random()*255);

				color[i] = new Color(randomR, randomB, randomG, 1.0f); // the 1.0f is the alpha 
				page.setColor (color[i]);
    			page.fillPolygon (xX, yX, xX.length); 
    		}    

[Gregg Bolinger]

Check the API. It tells you what kinds of arguments the Color constructor takes. Here's a hint, you can't mix int's and float's.

[Campbell Ritchie]

Sounds like a Swing-related topic. Moving.

[Jonathan Haybok]

Seems like I'm missing something here...

I tried changing them to floats, but then that was incompatible. So I tried this other format, which doesn't work.

ERROR: Exception in thread "AWT-EventQueue-0" java.lang.ArrayIndexOutOfBoundsException: 9

   for (int i=0; i<10; i++) 
			{ 
				int randomR = (int) (Math.random()* 255);
         	int randomB = (int) (Math.random()* 255);
         	int randomG = (int) (Math.random()* 255);

				color[i] = new Color(randomR, randomB, randomG); // the 1.0f is the alpha 
				page.setColor (color[i]);
    			page.fillPolygon (xX, yX, xX.length); 
    		}