如何根据第一个微调器中的选择从数据库中过滤第二个微调器值？

Question

I am setting a new activity named Dispatch Report, which has two Spinners: CustomerSpinner and LotSpinner.

LotSpinner shows all Lots in Dispatch Table instead of showing only those Lots which are related to the Customer selected in the first Spinner.

I have fetched CustomerSpinner Value from Dispatch Table. In LotSpinner also fetched Lot numbers from Dispatch Table, but not Filtered according to customer selection.

DispatchReportActivity.Java

// Fetching customer from dispatch table  
private void loadCustomerNameDispatch() {
    DatabaseHelper db = new DatabaseHelper( getApplicationContext() );

        List<String> lables1 = db.getFirmNAmeMoveStock();
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, lables1);
        dataAdapter           .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // attaching data adapter to spinner
        spinCustomer.setAdapter(dataAdapter);
        spinCustomer.setOnItemSelectedListener(this);
    }

// Fetching lot from dispatch table
    private void loadLotbyCustomerDispatch() {
        // database handler
        DatabaseHelper db = new DatabaseHelper(getApplicationContext());
        // Spinner Drop down elements
        List<String> lables = db.getLotbyCustomer();
        // Creating adapter for spinner
        ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this,
                android.R.layout.simple_spinner_item, lables);
        // Drop down layout style - list view with radio button
        dataAdapter
                .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        // attaching data adapter to spinner
        spinLotbyCustomer.setAdapter(dataAdapter);
    }

DATABASEHELPER.Java

//Get firm name in Dispatch Stock Report screen
public List < String > getFirmNAmeMoveStock() {
    List < String > labels = new ArrayList < String > ();

    // Select all query
    String selectQuery = "SELECT * FROM " + Table_Inventory;
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    // Looping through all rows and adding to list
    if (cursor.moveToFirst()) {
        do {
            labels.add(cursor.getString(3));
            Set < String > set = new HashSet < >(labels);
            labels.clear();
            labels.addAll(set);
        } while ( cursor . moveToNext ());
    }

    // Closing connection
    cursor.close();
    db.close();

    // Returning lables
    return labels;
}

// Method to get Lot No. in Dispatch Stock Report Activity
public List < String > getLotbyCustomer() {
    List < String > labels1 = new ArrayList < String > ();

    // Select all query
    String selectQuery = "SELECT * FROM " + Table_StockDispatch;
    SQLiteDatabase db = this.getReadableDatabase();
    Cursor cursor = db.rawQuery(selectQuery, null);

    // looping through all rows and adding to list
    if (cursor.moveToFirst()) {
        do {
            labels1.add(cursor.getString(4));
            Set < String > set = new HashSet < >(labels1);
            labels1.clear();
            labels1.addAll(set);
        } while ( cursor . moveToNext ());
    }

    // Closing connection
    cursor.close();
    db.close();

    // Returning lables
    return labels1;
}

There will be multiple customers, and each customer could have multiple Lots, so I want the second spinner to show only those Lots which are relevant to the customer selected in the first Spinner.

Answer 1

I'd suggest utilising Cursor's and Cursor adapters which can make matter simpler as :-

• there is no need for intermediate arrays (one of your issues is that String arrays do not provide sufficient information)
• CursorAdapters are designed to handle id (albiet a requirement that these exists in the Cursor with the column name _id (see the use of BaseColumns._ID below)).

The following is a basic example of related spinners based loosely upon your requirements.

First the DatbaseHelper DatabaseHelper.java

Two tables are defined/created Customers and Lots, methods to add data for each exist as do methods to extract a list from each of the tables. The lots extracted are based upon the customer to which they reference/belong to/associate with.

public class DatabaseHelper extends SQLiteOpenHelper {

    public static final String DBNAME = "mydb";
    public static final int DBVERSION = 1;
    public static final String TBL_CUSTOMER = "customer";
    public static final String TBL_LOT = "lot";


    public static final String COL_CUSTOMER_ID = BaseColumns._ID; //<<<<<<<<<< column name is _id (needed for Cursor Adapter)
    public static final String COL_CUSTOMER_NAME = "customer_name";

    public static final String COL_LOT_ID = BaseColumns._ID; //<<<<<<<<<< column name is _id (needed for Cursor Adapter)
    public static final String COL_LOT_NAME = "lot_name";
    public static final String COL_LOT_CUSTOMERREFERENCE = "customer_refererence";

    SQLiteDatabase mDB;

    public DatabaseHelper(Context context) {
        super(context, DBNAME, null, DBVERSION);
        mDB = this.getWritableDatabase(); //<<<<<<<<<< get the database connection (force create when constructing helper instance)
    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        String crt_customer_table_sql = "CREATE TABLE IF NOT EXISTS " + TBL_CUSTOMER + "(" +
                COL_CUSTOMER_ID + " INTEGER PRIMARY KEY, " +
                COL_CUSTOMER_NAME + " TEXT UNIQUE " +
                ")";

        String crt_lot_table_sql = "CREATE TABLE IF NOT EXISTS " + TBL_LOT + "(" +
                COL_LOT_ID + " INTEGER PRIMARY KEY, " +
                COL_LOT_NAME + " TEXT, " +
                COL_LOT_CUSTOMERREFERENCE + " INTEGER " +
                /*?????????? OPTIONAL IF FOREIGN KEYS ARE TURNED ON
                "REFERENCES " + TBL_CUSTOMER + "(" +
                COL_CUSTOMER_ID +
                ")" +
                */
                ")";
        db.execSQL(crt_customer_table_sql);
        db.execSQL(crt_lot_table_sql);

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

    }

    public long addCustomer(String name) {
        ContentValues cv = new ContentValues();
        cv.put(COL_CUSTOMER_NAME,name);
        return mDB.insert(TBL_CUSTOMER,null,cv);
    }

    public long addLot(String name, long customer_reference) {
        ContentValues cv = new ContentValues();
        cv.put(COL_LOT_NAME,name);
        cv.put(COL_LOT_CUSTOMERREFERENCE,customer_reference);
        return mDB.insert(TBL_LOT,name,cv);
    }

    public Cursor getCustomers() {
        return mDB.query(TBL_CUSTOMER,null,null,null,null,null,COL_CUSTOMER_NAME);
    }

    public Cursor getLotsPerCustomer(long customer_id) {
        String whereclause = COL_LOT_CUSTOMERREFERENCE + "=?";
        String[] whereargs = new String[]{String.valueOf(customer_id)};
        return mDB.query(TBL_LOT,null,whereclause,whereargs,null,null,COL_LOT_NAME);
    }
}

• Note the above is pretty straight-forward. However, it would obviously need to be adapted to suit you App.

The second code is the activity that utilises the above and incorporates the 2 linked/related spinners where the selectable Lots are as per those lots associated with the currently selected customer.

The layout used for the activity is very basic, it just has two spinners. The spiners use the stock Simple_List_Item_2 layout (2 has been used to allow the all important ID's to be viewed (typically the user would not be shown the ID's)).

In short whenever a selection is made in the Customer spinner the Lot spinner is managed (setup or refreshed) based upon the customer id which is used to select the related/reference lots.

public class MainActivity extends AppCompatActivity {

    Context mContext;
    DatabaseHelper mDBHlpr;
    SimpleCursorAdapter mCustomerSCA, mLotSCA;
    Spinner mCustomerList, mLotList;
    Cursor mCustomers, mLots;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mContext = this;
        mDBHlpr = new DatabaseHelper(this);
        mCustomerList = this.findViewById(R.id.customer_list);
        mLotList = this.findViewById(R.id.lot_list);

        addTestingDataIfNoData(); //Go and add some testing data if there is none
        manageCustomerSpinner();
    }

    private void manageCustomerSpinner() {
        mCustomers = mDBHlpr.getCustomers();
        if (mCustomerSCA == null) {
            mCustomerSCA = new SimpleCursorAdapter(
                    this,
                    android.R.layout.simple_list_item_2,
                    mCustomers,
                    new String[]{
                            DatabaseHelper.COL_CUSTOMER_NAME,
                            DatabaseHelper.COL_CUSTOMER_ID
                    },
                    new int[]{
                            android.R.id.text1,
                            android.R.id.text2
                    },
                    0
            );
            mCustomerList.setAdapter(mCustomerSCA);

            mCustomerList.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
                @Override
                public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                    manageLotSpinner(id); //<<<<<<<<<< WHENEVER CUSTOMER IS SELECTED THE LOT SPINNER IS MANAGED >>>>>>>>>>
                }

                @Override
                public void onNothingSelected(AdapterView<?> parent) {

                }
            });
        } else {
            mCustomerSCA.swapCursor(mCustomers);
        }
    }

    private void manageLotSpinner(long id) {
        mLots = mDBHlpr.getLotsPerCustomer(id);
        if (mLotSCA == null) {
            mLotSCA = new SimpleCursorAdapter(
                    this,
                    android.R.layout.simple_list_item_2,
                    mLots,
                    new String[]{
                            DatabaseHelper.COL_LOT_NAME,
                            DatabaseHelper.COL_LOT_ID
                    },
                    new int[]{
                            android.R.id.text1,
                            android.R.id.text2
                    },
                    0
            );
            mLotList.setAdapter(mLotSCA);
        } else {
            mLotSCA.swapCursor(mLots);
        }
    }


    private void addTestingDataIfNoData() {
        if (DatabaseUtils.queryNumEntries(mDBHlpr.getWritableDatabase(),DatabaseHelper.TBL_CUSTOMER) < 1) {
            mDBHlpr.addCustomer("Fred");
            mDBHlpr.addCustomer("Mary");
            mDBHlpr.addCustomer("Sue");
            mDBHlpr.addCustomer("Alan");

            mDBHlpr.addLot("Lot001",2); // Lot for mary
            mDBHlpr.addLot("Lot002",1); // Lot for fred
            mDBHlpr.addLot("Lot003",4); // Lot for ala
            mDBHlpr.addLot("Lot004",3); // Lot for sue
            mDBHlpr.addLot("Lot005",3); // Lot for sue
            mDBHlpr.addLot("Lot006",3); // Lot for use
            mDBHlpr.addLot("Lot007",2); // Lot for mary
            mDBHlpr.addLot("Lot008",2); // Lot for mary
            mDBHlpr.addLot("Lot009",2); // Lot for mary
            mDBHlpr.addLot("Lot0010",2); // Lot for mary
            mDBHlpr.addLot("Lot0020",1); // Lot for Fred
            mDBHlpr.addLot("Lot00130",4); // Lot for Alan
            mDBHlpr.addLot("Lot00130",3); // Lot for Sue
        }
    }
}  

Result Example

Initial

• Alan is initial selection due to sort order

After Selecting Mary

• Note Lot names, as used, are not really suited to sorting