how to add list data from Room database to Alert Dialog in android

Question

I Am using Room database and I want to retrieve data from Category table and display that in Alert Dialog

final List<Category> categories = database.getQuery().getByCategory("Income");

but there it is showing error like this:

error: no suitable method found for setItems(List<Category>,<anonymous android.content.DialogInterface.OnClickListener>)
method Builder.setItems(int,android.content.DialogInterface.OnClickListener) is not applicable
(argument mismatch; List<Category> cannot be converted to int)
method Builder.setItems(CharSequence[],android.content.DialogInterface.OnClickListener) is not applicable
(argument mismatch; List<Category> cannot be converted to CharSequence[])

package com.example.mybugetssimple;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.coordinatorlayout.widget.CoordinatorLayout;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.ListAdapter;
import android.widget.Spinner;
import android.widget.SpinnerAdapter;
import android.widget.TextView;

import com.example.mybugetssimple.database.Category;
import com.example.mybugetssimple.database.ExpenseDatabase;
import com.google.android.material.snackbar.Snackbar;

import java.util.List;


public class AddExpenseActivity extends AppCompatActivity{

    TextView Date,catType;
    EditText amount,desc;
    ExpenseDatabase database;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add_expense);

        //Add back Button
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        catType = findViewById(R.id.addExInputTv);
        Date =findViewById(R.id.addExDateInputTv);
        amount = findViewById(R.id.addExAmountInputEt);
        desc = findViewById(R.id.addExDesInputEt);
        database = ExpenseDatabase.getDatabaseInstance(this);

        final List<Category> categories = database.getQuery().getByCategory("Income");


        System.out.println(categories);

        catType.setOnClickListener( new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                final AlertDialog.Builder builder = new AlertDialog.Builder(AddExpenseActivity.this);
                builder.setTitle( "Select Income Category" );
                builder.setItems( categories, new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        catType.setText(categories.get(which).getCategory_name());
                    }
                } );

                builder.setNegativeButton( "CANCEL", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        builder.setCancelable( true );
                    }
                } );

                builder.setPositiveButton( "OK", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        if (which == -1) {

                        } else {
                            catType.setText( categories.get(which).getCategory_name());

                        }
                    }
                } );
                AlertDialog alertDialog = builder.create();
                alertDialog.show();

            }
        } );
    }

    public boolean onOptionsItemSelected(@NonNull MenuItem item) {

        int id = item.getItemId();
        if(id == android.R.id.home){
            this.finish();
        }

        return super.onOptionsItemSelected(item);
    }
}

Doa file:

package com.example.mybugetssimple.database;

import androidx.lifecycle.LiveData;
import androidx.room.Dao;
import androidx.room.Insert;
import androidx.room.OnConflictStrategy;
import androidx.room.Query;

import java.util.List;

@Dao
public interface QueryDao {

    @Insert
    void category(Category ob);
    @Insert
    void category(Category...ob);

    @Insert
    void expense(Expense ob);
    @Insert
    void expense(Expense...ob);

    @Insert
    void income(Income ob);
    @Insert
    void income(Income...ob);

    @Insert
    void register(Register ob);

    @Insert(onConflict = OnConflictStrategy.IGNORE)
    void registerUser(Register ob);

    @Query("SELECT * FROM Category")
    LiveData<List<Category>> getAllCategoryList();
    @Query("SELECT * FROM EXPENSE")
    List<Expense> getAllExpenseList();
    @Query("SELECT * FROM INCOME")
    List<Income> getAllIncomeLIst();

    @Query("SELECT * FROM REGISTER WHERE Email=:emailId and password=:passwordId")
    Register getUser(String emailId, String passwordId);

    @Query("SELECT *FROM Register")
    List<Register> getUser();

    @Query("SELECT Email FROM REGISTER WHERE Email =:emailId")
    Register getEmail(String emailId);

    @Query("SELECT category_id, category_name FROM CATEGORY WHERE category_type =:catType")
     List<Category> getByCategory(String catType);
}

//

Answer 1

Afaik setItems receives a String array. So it looks like You should generate String[] catNames that will contain names of the categories, and use it with setItems.

After user presses ok, You should look for a category with category_name as one that was selected in a dialog.

final AlertDialog.Builder builder = new AlertDialog.Builder(AddExpenseActivity.this);
        builder.setTitle( "Select Income Category" );

        String[] catNames = new String[categories.size()];
        for (int i=0; i<categories.size(); i++ ){
            catNames[i] = categories.get(i).getName();
        }

        builder.setItems( catNames, new DialogInterface.OnClickListener() {....