Fill ArrayList with colors for Android

Question

I want to create 2 ArrayList. One holding 16 colors, the other one holding 139.

I have the list with colors (both RGB as 255,126,32 and Hex as 0xFFFF2552). I want to use

Answer 1

You could try:

int[] colors = new int[] {Color.rgb(1,1,1), Color.rgb(...)};

For example, but I don't think it's a good idea to decide only using "one line" argument.

List<Integer> coloras = Arrays.asList(new Integer[]{Color.rgb(1, 1, 1), Color.rgb(...)});

Will also work.

You can create an arraylist in arrays.xml file:

<resources>
    <string-array name="colors">        
        <item>#ff0000</item>
        <item>#00ff00</item>  
        <item>#0000ff</item>
    </string-array>
</resources>

Then use the loop to read them:

String[] colorsTxt = getApplicationContext().getResources().getStringArray(R.array.colors);
List<Integer> colors = new ArrayList<Integer>();
for (int i = 0; i < colorsTxt.length; i++) {
    int newColor = Color.parseColor(colorsTxt[i]);
    colors.add(newColor);
}

In my opinion keeping colors in the list is the most convinient solution.

To take a color from the list randomly, you do:

int rand = new Random().nextInt(colors.size());
Integer color = colors.get(rand);

Answer 2

I would make a text file or xml file populated with the color info and have a function that reads in each line of the file using a loop, creates a Color object for each line and adds it to the array list and then goes to the next line until there are no lines left.

Answer 3

You can also can use int[] colors = new int[]{color1.getRGB(),color2.getRGB()}; And decode using: Color color = new Color(colors[0]);

Answer 4

I would recommend against using a configuration file unless you want to be able to change your colors without code changes. I suspect your colors are constant though, so the file would just add unnecessary complexity to your application.

The code sample in your question assumes java.awt.Color when you would actually use the utility class android.graphics.Color which cannot be instantiated.

Therefore I recommend the following solution as a static variable (and be careful not to modify the contents of the array later):

static final int[] colors16 = {
  Color.rgb(255, 0, 0),
  Color.rgb(0, 255, 0),
  Color.rgb(0, 0, 255)
};

Now add a static instance of Random to use for selecting random colors from the list.

static final Random random = new Random();

And then pick your color!

int colorIndex = random.nextInt(colors16.size());
Color color = colors16.get(colorIndex);

If you feel it's important to protect the contents of your list, you can make it immutable as follows, at the small expense of boxing your color ints into Integer objects.

static final List<Integer> colors = Collections.unmodifiableList(
  Arrays.asList(
    Integer.valueOf(Color.rgb(255, 0, 0)),
    Integer.valueOf(Color.rgb(0, 255, 0)),
    Integer.valueOf(Color.rgb(0, 0, 255))
  )
);

Technically you can leave out the Integer.valueOf() conversion in the above snippet and Java will autobox the ints.

Answer 5

What you have looks like it makes sense, but you should specify the type of the ArrayList.

List<Color> colorList = new ArrayList<Color>();
colorList.add(cBlue);
... etc

(The difference between declaring it as a List or an ArrayList is that List is the interface that ArrayList implements. This is a generally pretty good practice, but for your purposes it probably won't make a difference if you declare it as a List or an ArrayList).

If you want to do it in fewer lines of code, you can use an ArrayList initializer block, like this:

List<Color> colorList = new ArrayList<Color> { new Color(...), cBlue };

Or with Arrays.asList, which takes in an array and returns a List.

But in general you should get used to verbosity with Java, don't try to optimize your lines of code so much as the performance of those lines.

(Sidenote: make sure you're using the correct Color class. There's android.graphics.Color and java.awt.Color, and they're totally different, incompatible types. The constructor you're using is from java.awt.Color, and with Android you're probably going to want to use android.graphics.Color).