Question

ListViews have always been my weak point and right now I am practicing putting a Listview, within a Listview. Anyway, I first call my ListView at the start of my program and it loads it with an array saved in my strings.xml:

String[] departments = getResources().getStringArray(
                R.array.departments_array);
        setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item,
                departments));
        setContentView(R.layout.main);

        ListView lv = getListView();
        lv.setTextFilterEnabled(true);

What I want to do is update this ListView with a new array of values each time a list item is clicked. The reason why I am trying to do it this way is because I plan on having 27 different arrays with different values for each position, and I feel it would be lighter on my resources if instead of making a ListView for each array of items, I would update this one ListView. I know I am probably not doing this the most efficient way, but if there is another way of implementing my idea please tell me.

   lv.setOnItemClickListener(new OnItemClickListener() {
                public void onItemClick(AdapterView<?> parent, View view,
                        int position, long id) {
                    // When clicked, show a toast with the TextView text
                    switch (position) {
                    case 0:
                        try {


    //It is here that i dont know what to do, I was going to call 
//the Listview the same way i did previously using my setlistadapter, 
//but i kept getting errors about the code being undefined


                            String[] listitems1 = getResources().getStringArray(
                                    R.array.items_array);

                        } catch (ClassCastException e) {
                            Toast.makeText(getApplicationContext(), "Error",
                                    Toast.LENGTH_SHORT).show();
                        }
                        break;
                    case 1:
                        try {
                      //The listview will be changed again here
                        } catch (ClassCastException e) {
                            Toast.makeText(getApplicationContext(), "Error",
                                    Toast.LENGTH_SHORT).show();
                        }
                        break;
                    }
                };

            });

Answer 1

Your approach is wrong( if I understand what are you doing). Instead of replacing the adapter of the ListView every time the user clicks(and simply setting a new adapter should work) a element in the initial list you should start a new activity passing the clicked position and in your new activity set the adapter on a ListView with the correct array based on that position.

A small example:

Main class:

/**
 * The main class with the initial 27 items array.
 */
public class Class1 extends ListActivity {

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        // start the second activity that will show our array depending on the
        // position clicked
        Intent i = new Intent(this, Class2.class);
        // put the position in the Intent so we can know in the other activity
        // what array to load.
        i.putExtra("pos", position);
        startActivity(i);
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // I just used a simple array of 2 items, you'll load your 27 items
        // array
        String[] items = { "1", "2" };
        setListAdapter(new ArrayAdapter<String>(this,
                android.R.layout.simple_list_item_1, items));
    }

}

Secondary activity that will show the array based on the previously selected position:

public class Class2 extends ListActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // get the Intent that started the activity
        Intent i = getIntent();
        // find out what position did that other activity send to us.
        int position = i.getIntExtra("pos", -1);
        // load the ListView with an adapter based on the array that you
        // want(according to that position)
        if (position == 0) {
            // the first element in the main list
            String[] items = getResources().getStringArray(R.array.a1);
            setListAdapter(new ArrayAdapter<String>(this,
                    android.R.layout.simple_list_item_1, items));
        } else if (position == 1) {
            // the second element in the main list
            String[] items = getResources().getStringArray(R.array.a2);
            setListAdapter(new ArrayAdapter<String>(this,
                    android.R.layout.simple_list_item_1, items));
        } else {
            // etc
        }
    }

}