Loop to randomly display Images from Array (Android)

Question

I have an array of 5 images (R.drawable.one, R.drawable.two,R.drawable.three, R.drawable.four, and R.drawable.five). Previously, my program would pick 5 random images from these and display them randomly on the screen without any errors. I then added myImgCount and totalImgCount because I want to give each image an int value. For example: R.drawable.one would be equal to 1, R.drawable.two would be equal to 2...etc. I then want my for loop to keep track of the images placed using myImgCount and then run until totalImgCount is equal to 50. After I added myImgCount and totalImgCount I now have an error:

"11-26 18:22:16.750: E/AndroidRuntime(13971): FATAL EXCEPTION: Thread-33401 E/AndroidRuntime(13971): java.lang.NullPointerException"

on Bitmap bmp = BitmapFactory.decodeResource(getResources(), array1[i]);

Here is the code I have so far:

public void surfaceCreated(SurfaceHolder holder) {

ArrayList<Integer> list = new ArrayList<Integer>();

    Random r = new Random();

    int[] images = new int[] { R.drawable.one, R.drawable.two,
        R.drawable.three, R.drawable.four, R.drawable.five };

    int totalImgCount = 0;


    for (int i = 0; i<50; i++)
    {
        while (true) 
        {
            int myImgCount = r.nextInt(5);

                 totalImgCount += myImgCount + 1;

            if (totalImgCount<50) {

                list.add(images[myImgCount]);   //do it again if not yet at 50
                break;
            }
                   totalImgCount -= (myImgCount + 1);
        }

    }

    array1 = convertIntegers(list);

    }

The next part of my code that is used to give the images int values:

public static int[] convertIntegers(List<Integer> integers) {
    int[] ret = new int[integers.size()];
    Iterator<Integer> iterator = integers.iterator();
    for (int i = 0; i < ret.length; i++) {
        ret[i] = iterator.next().intValue();
    }
    return ret;
}

Before getting this error my program would run without errors and display 5 random images on the screen. As I mentioned above I am trying to create a loop that keeps displaying random images until the total sum of the images is 50. Let me know if you need any more info! I appreciate any help and thanks in advance!

EDIT: Left out my render method where I"m getting the error:

public void render(Canvas canvas) {

    if (canvas != null) {

        Random random = new Random();
        canvas.drawRGB(234, 237, 235);

        for (int i=0; i<50; ++i) { 
          Bitmap bmp = BitmapFactory.decodeResource(getResources(), 
array1[i]);            //This is where I am currently getting the error
          canvas.drawBitmap(bmp,random.nextInt(canvas.getWidth()-bmp.getWidth
                      ()), random.nextInt
                        (canvas.getHeight()-bmp.getHeight()),null);

        }
    }

}

Answer 1

It sounds like you're not restricting your random numbers to the array indexes (0-4). Start with this to constrain your numbers between 0 and 4.

    int range = images.length-1;        
    int myImgCount = 0;

    Random random = new Random();
    for( int i = 0; i < 50; ++i)
    {
        myImgCount = random.nextInt(range);
        list.add(images[myImgCount]);
    }

Adjust your render method, see if this will help:

    if (canvas != null)
    {             
         Random random = new Random();
         canvas.drawRGB(234, 237, 235);

         //iterate over your integer array
         //there should be 50 resource ids available
         for(int resourceId : array1)
         {
               Bitmap bmp = BitmapFactory.decodeResource(getResources(), resourceId);
               //This is where I am currently getting the error
               canvas.drawBitmap(bmp, 
                     random.nextInt(canvas.getWidth()-bmp.getWidth()), 
                     random.nextInt(canvas.getHeight()-bmp.getHeight()), null);

         }    
     }

I would also change the following:

for (int i = 0; i<50; i++)
{
    while (true) 
    {
        int myImgCount = r.nextInt(5);

             totalImgCount += myImgCount + 1;

        if (totalImgCount<50) {

            list.add(images[myImgCount]);   //do it again if not yet at 50
            break;
        }
               totalImgCount -= (myImgCount + 1);
    }

}

Possible change:

 int i = 0;

 while(i < 50)
 {
      //calculate random resource ids from your resource array here and add them to your array1
      i++;
 }