Question

I have a problem on Android Spinner.In my application I created two Spinner on main layout. ‘State’ Spinner and ‘District’ Spinner. All the data on Spinner are stored in SQLite database. I want do display list of ‘District’ on second spinner depending on selection of particular ‘State’ in the first spinner.
Example: Suppose when I select Karnataka in the first spinner then application first retrieve all the district from SQLite database related to karnataka state and then it display on second Spinner.

For this I do all the database activity correctly means creating two table ‘state’ and ‘district’ in which one column in district table is foreign key which is refereed to one of the primary key of ‘state table’

db.execSQL("create table "+STATE_TABLE+" ("+
            STATE_ID+" integer primary key autoincrement not null, "+
                STATE_NAME+" text"+")");

    db.execSQL("create table "+DISTRICT_TABLE+" ("+DISTRICT_ID+
            " integer primary key autoincrement not null,"+DISTRICT_NAME
                +" text,"+STATE_ID+" integer, FOREIGN KEY("
                    +STATE_ID+") REFERENCES "+STATE_TABLE
                        +"("+STATE_ID+")"+")");

Now in the Activity Class:

spinnerState = (Spinner)findViewById(R.id.spinner1);
spinnerDistrict = (Spinner)findViewById(R.id.spinner2);
stateList = new ArrayList<String>();
districtList = new ArrayList<String>();

Suppose all the data are all ready stored in database.

Now I need to retrieve all the ‘State’ data from database and add it in the statelist which is ArrayList.

Cursor stateCursor = database.query(STATE_TABLE, new String[]{STATE_ID, STATE_NAME},
            null, null, null, null, STATE_NAME);
    stateCursor.moveToFirst();

    if(! stateCursor.isAfterLast()){
        do{
            int id = stateCursor.getInt(0);
            String stateName = stateCursor.getString(1);
            stateList.add(stateName);
        }while(stateCursor.moveToNext());
    }
    stateCursor.close();

after this I create one ArrayAdapter and put this state list into this.

spinnerState.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, stateList));

Next i put the following code in the activity class:

spinnerState.setOnItemSelectedListener(new OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> parent, View v,
                int pos, long id) {

        }

        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
            // TODO Auto-generated method stub
        }
    });

Now My problem is here:

1. How I get the StateId for executing the select query for taking all the district related to particular state in database.
2. How the adapter will generate for District.
3. where I put all these code.

Here what I need creating the districtList after getting the value from state Spinner.

Similar Question which asked earlier in this website, what they do:
they already create two adapter for two spinner and then apply setOnItemSelectedListener.
Please Help me because here my mind totally stop working.
I refer lot of book and website but not they even mention these type of problem.

Answer 1

I see a couple of solutions here:

Option 1:

Instead of declaring stateList as an ArrayList<String>, create a custom POJO StateInfo and designate stateList as ArrayList<StateInfo>

public class StateList {
    private int id;
    private String stateName;

    //Constructors, getters and setters
}

Then,

if(! stateCursor.isAfterLast()){
    do{
        int id = stateCursor.getInt(0);
        String stateName = stateCursor.getString(1);
        stateList.add(new StateInfo(id, stateName));
    }while(stateCursor.moveToNext());
}

Now, you can do this:

public void onItemSelected(AdapterView<?> parent, View v,
        int pos, long id) {
    int id = stateList.get(pos).getId();
    //Use This ID to construct your next SQLite query; and populate the district spinner.
}

If you do this, you will have to create a custom ArrayAdapter and implement the getView() method. Look at the Android docs for how to do this.

Option 2:

Why do you even need the stateID? I suppose you can write a Query to get the districts list given a state Name only. In that case, you can retain the stateList as an ArrayList<String> and you don’t even need the StateInfo class at all. Just do this:

public void onItemSelected(AdapterView<?> parent, View v,
        int pos, long id) {
    String stateName = stateList.get(pos);
    //Use this name to construct your next SQLite query; and populate the district spinner.
}