Access variables by name in a loop

Question

I'm working on an Android project, and i have a lot of drawables. These drawables are all named like icon_0.png, icon_1.png ... icon_100.png. I want to add all the resource id's of these drawables to an ArrayList of Integers. (For those, who do not know android, only Java, i am talking about static variables, in a static inner class of a class, like R.drawable.icon_0. All of this static variables are Integers.)

Is there a more efficient way to do this, than adding them one by one? Like

ArrayList<Integer> list = new ArrayList<Integer>();
list.add(R.drawable.icon_1);
list.add(R.drawable.icon_2);
...
list.add(R.drawable.icon_100);

Can i loop through them somehow? Like

for(int i=0; i<100; i++)
{
    list.add(R.drawable.icon_+i);  //<--- I know this doesn't work.
}

I have no control over the file where these static integers are, and i cannot create the drawables in runtime.

Any help would be appreciated!

EDIT

Okay, i read the answers, but i have one major problem: I don't have access to any Context instances where i need to create this array/list of ids (i do it in a static initialzer block), so the getResources() method, what two of the answers suggested wont work. Is there any other way of doing this?

Answer 1

Create an XML file in the values folder in your resource directory.

<?xml version="1.0" encoding="utf-8"?>
<resources>
<array name="myIcons">
    <item>@drawable/icon1</item>
    <item>@drawable/icon2</item>
    <item>@drawable/icon3</item>
    <item>@drawable/icon4</item>
    <item>@drawable/icon5</item>
    ...
    ...
</array>
</resources>

Go through the following code, you will get the idea.

Resources res = getResources();
TypedArray myIcons= res.obtainTypedArray(R.array.myIcons);  //mentioned  in the XML
for(int i=0; i<100; i++)
{
    Drawable drawable = myIcons.getDrawable(i);
    list.add(drawable);  
}

Answer 2

You can try this. YourClassName.class.getFields();

Field[] fields = R.drawable.class.getFields();

you can iterate all fields, and you may need to filter it if u have additional fields than you need.

Answer 3

One way would be to use reflection API.

Something along the lines...

Field[] fields =  R.drawable.class.getFields();
List<String> names = new ArrayList<String>(); 
for (Field field : fields) {
    if(field.getName().startsWith("icon")) 
       names.add(field.getName());    
}

int resid = getResources().getIdentifier(names.get(0), "drawable", "com.org.bla");

I haven't tested this, but you get the idea.

Answer 4

Here is what i ended up doing:

icons = new ArrayList<Integer>(100);

//get all the fields of the R.drawable class.       
Field  [] fields = R.drawable.class.getDeclaredFields();

//create a temporary list for the names of the needed variables.
ArrayList <String> names = new ArrayList<String>(100);

//select only the desired names.
for(int i=0; i<fields.length; i++)
    if(fields[i].getName().contains("icon_"))
        names.add(fields[i].getName());

//sort these names, because later i want to access them like icons.get(0)
//what means i want icon_0.
Collections.sort(names);

try
{
    for(int i=0; i<names.size(); i++)
    {
        //get the actual value of these fields, 
        //and adding them to the icons list.
        int id = R.drawable.class.getField(names.get(i)).getInt(null);
        icons.add(id);
    }
}
catch(Exception ex)
{
    System.out.println(ex.getMessage());
}

I'm sure, that it's not the fastest way but it's working. I will accept AljoshaBre's solution, because his answer led me to this solution.

Thanks everybody for the help!