how to find view by id using a string variable?

Question

I'm writing an android app and I'm trying to initialize a grid of buttons in with a nested loop.

i originally found this current solution through research but i cant figure out whats going wrong.

for (int i = 0; i < piles.length; i++)
  for (int j = 0; j < piles[0].length; j++) {

        id = getResources().getIdentifier("R.id." + "b" + numplayaz + Integer.toString(i) + Integer.toString(j), "id","app.dj");
        bpiles[i][j] = ((Button) this.findViewById(id));
        bpiles[i][j].setOnClickListener(this);
   }
 }

for some reason when id is always set to 0 and thus bpiles[0][0] is set to null, and then get a null pointer exception.

i'v tried allot of little solutions but nothing has worked.

does anyone either see what my problem is or have a better solution to this.

oh, and i came up with this when i saw this post. Android findViewbyId with a variant string

Is your package name really `app.dj`, have you tried using `getPackageName()` instead? Also post how you set each button's id. — Sam, Nov 24 '12 at 19:50

Sam · Accepted Answer · 2012-11-24T21:28:16.657

It looks like the first parameter of getIdentifier() is wrong:

id = getResources().getIdentifier("R.id." + "b" + numplayaz + Integer.toString(i) + Integer.toString(j), "id","app.dj");
//             Do not use "R.id." ^^^^^^^

We already know that you are trying to reference R and the second parameter specifies the type "id". Change it too:

id = getResources().getIdentifier("b" + numplayaz + Integer.toString(i) + Integer.toString(j), "id", "app.dj");

Also String's + operator should take precedence, so you can "b" + numplayaz + i + j. But a StringBuilder might be your fastest approach and easier to read.

score 0 · Answer 2 · answered Nov 24 '12 at 19:58

0

0 means that the id is not found.

Have you checked that all the ids you are referencing exist?
Use getPackageName() instead of "app.dj". Maybe it's incomplete.

answered Nov 24 '12 at 19:58

User

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score 0 · Answer 3 · answered Nov 24 '12 at 20:01

0

Once you build your drawable name, you can use this function to get its Id:

public static int getDrawableByName( String name ) {
    int drawableId = 0;

    try {
         Class res = R.drawable.class;
         Field field = res.getField( name );
         drawableId = field.getInt(null);
    }
    catch (Exception e) {
        e.printStackTrace();
    }

    return drawableId;
}

answered Nov 24 '12 at 20:01

Marcin Orlowski

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Where are drawables mentioned? – Sam Nov 24 '12 at 21:31

how to find view by id using a string variable?

3 Answers3