How to implement various functionalities in Android Studio: Intents, AlertDialog, NotificationManager, MediaPlayer, and SQLite Database operations?

HiMr
April 12, 2024
279 views
3 votes
4 Answers

I’m developing an Android application in Android Studio and I’m in need of assistance with implementing several fundamental functionalities. Specifically, I require guidance on:

Using Intents for navigation between activities.
Displaying messages to the user using AlertDialog.
Sending notifications using NotificationManager.
Implementing MediaPlayer for audio playback.
Creating and managing a SQLite database, including table creation, inserting values, and fetching data based on conditions, using a DatabaseHelper class.
I’ve explored documentation and tutorials for each of these topics, but I’m struggling to integrate them effectively into my project.

Could someone please provide comprehensive examples or code snippets demonstrating the proper implementation of these functionalities in Android Studio, either in Java or Kotlin? Additionally, any insights into best practices or common pitfalls to avoid would be greatly appreciated.

I’ve explored documentation and tutorials for each of these topics, but I’m struggling to integrate them effectively into my project.

Answers

Chosen as BEST ANSWER

Example of a database helper program --

package com.example.l7q1;

import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {

private static final String DATABASE_NAME = "student.db";
private static final int DATABASE_VERSION = 1;

private static final String TABLE_NAME = "student";
private static final String COLUMN_ID = "id";
private static final String COLUMN_ROLL_NUMBER = "roll_number";
private static final String COLUMN_NAME = "name";
private static final String COLUMN_MARKS = "marks";

public DatabaseHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    String createTableQuery = "CREATE TABLE " + TABLE_NAME + " ("
            + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
            + COLUMN_ROLL_NUMBER + " VARCHAR, "
            + COLUMN_NAME + " VARCHAR, "
            + COLUMN_MARKS + " VARCHAR)";
    db.execSQL(createTableQuery);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
    onCreate(db);
}

public boolean addStudent(String rollNumber, String name, String marks) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues contentValues = new ContentValues();
    contentValues.put(COLUMN_ROLL_NUMBER, rollNumber);
    contentValues.put(COLUMN_NAME, name);
    contentValues.put(COLUMN_MARKS, marks);
    long result = db.insert(TABLE_NAME, null, contentValues);
    return result != -1;
}

public Cursor getAllStudents() {
    SQLiteDatabase db = this.getWritableDatabase();
    return db.rawQuery("SELECT * FROM " + TABLE_NAME, null);
}

// Inside DatabaseHelper.java
public boolean updateStudent(String rollNumber, String name, String marks) {
    SQLiteDatabase db = this.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(COLUMN_NAME, name);
    values.put(COLUMN_MARKS, marks);
    int affectedRows = db.update(TABLE_NAME, values, COLUMN_ROLL_NUMBER + "=?", new String[]{rollNumber});
    return affectedRows > 0;
}


public boolean deleteStudent(String id) {
    SQLiteDatabase db = this.getWritableDatabase();
    int deletedRows = db.delete(TABLE_NAME, "id=?", new String[]{id});
    return deletedRows > 0;
}

}

Popup Menu example --

Basic layout for first page with spinner example --

<Spinner
    android:id="@+id/spinner"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"/>

<Button
    android:id="@+id/okButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="OK"
    android:layout_below="@id/spinner"
    android:layout_alignParentStart="true"/>

<Button
    android:id="@+id/clickMeButton"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Click Me"
    android:layout_below="@id/spinner"
    android:layout_alignParentEnd="true"/>

main activity.java --

import android.os.Bundle; import android.view.MenuItem; import android.view.View; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.PopupMenu; import android.widget.Spinner; import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import java.util.ArrayList; import java.util.List;

public class MainActivity extends AppCompatActivity {

Spinner spinner;
Button okButton, clickMeButton;
List<String> itemsList = new ArrayList<>();
List<Integer> costsList = new ArrayList<>();

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

    spinner = findViewById(R.id.spinner);
    okButton = findViewById(R.id.okButton);
    clickMeButton = findViewById(R.id.clickMeButton);

    // Define items and their costs
    String[] items = {"Item1 - $25", "Item2 - $30", "Item3 - $15"};

    // Populate Spinner with items and costs
    ArrayAdapter<String> adapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, items);
    spinner.setAdapter(adapter);

    // OK button click listener
    okButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String selectedItem = spinner.getSelectedItem().toString();
            String[] parts = selectedItem.split(" - ");
            String itemName = parts[0];
            int itemCost = Integer.parseInt(parts[1].replace("$", ""));
            itemsList.add(itemName);
            costsList.add(itemCost);
        }
    });

    // Click Me button click listener
    clickMeButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            // Show a PopupMenu
            PopupMenu popupMenu = new PopupMenu(MainActivity.this, clickMeButton);
            popupMenu.getMenuInflater().inflate(R.menu.popup_menu, popupMenu.getMenu());
            popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
                @Override
                public boolean onMenuItemClick(MenuItem item) {
                    int itemId = item.getItemId();
                    if (itemId == R.id.menu_compute_average) {
                        computeAndDisplayAverage();
                        return true;
                    } else if (itemId == R.id.menu_list_values_above_average) {
                        listValuesAboveAverage();
                        return true;
                    } else if (itemId == R.id.menu_list_values_below_average) {
                        listValuesBelowAverage();
                        return true;
                    }
                    return false;
                }
            });
            popupMenu.show();
        }
    });
}

private void computeAndDisplayAverage() {
    if (costsList.isEmpty()) {
        Toast.makeText(MainActivity.this, "No items selected", Toast.LENGTH_SHORT).show();
        return;
    }

    int totalCost = 0;
    for (int cost : costsList) {
        totalCost += cost;
    }
    double average = totalCost / (double) costsList.size();
    Toast.makeText(MainActivity.this, "Average cost: $" + average, Toast.LENGTH_SHORT).show();
}


private void listValuesAboveAverage() {
    double totalCost = 0;
    for (int cost : costsList) {
        totalCost += cost;
    }
    double average = totalCost / costsList.size();

    List<String> aboveAverageItems = new ArrayList<>();
    for (int i = 0; i < costsList.size(); i++) {
        if (costsList.get(i) > average) {
            aboveAverageItems.add(itemsList.get(i) + " - $" + costsList.get(i));
        }
    }
    // Display above average items in a ListView or do something else with them
    Toast.makeText(MainActivity.this, "Items above average: " + aboveAverageItems.toString(), Toast.LENGTH_SHORT).show();
}

private void listValuesBelowAverage() {
    double totalCost = 0;
    for (int cost : costsList) {
        totalCost += cost;
    }
    double average = totalCost / costsList.size();

    List<String> belowAverageItems = new ArrayList<>();
    for (int i = 0; i < costsList.size(); i++) {
        if (costsList.get(i) < average) {
            belowAverageItems.add(itemsList.get(i) + " - $" + costsList.get(i));
        }
    }
    // Display below average items in a ListView or do something else with them
    Toast.makeText(MainActivity.this, "Items below average: " + belowAverageItems.toString(), Toast.LENGTH_SHORT).show();
}

}

(Edit)

Example of another db oriented student details app —

Mainactivity.java–

package com.example.l7q1;

import android.os.Bundle;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;

import android.database.Cursor;
import android.os.Bundle;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;

import android.database.Cursor;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;
import androidx.appcompat.app.AppCompatActivity;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private DatabaseHelper dbHelper;
    private ListView studentListView;
    private ArrayAdapter<String> adapter;
    private List<String> studentDetailsList;
    private EditText rollNumberEditText, nameEditText, marksEditText;

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

        dbHelper = new DatabaseHelper(this);

        rollNumberEditText = findViewById(R.id.rollNumberEditText);
        nameEditText = findViewById(R.id.nameEditText);
        marksEditText = findViewById(R.id.marksEditText);

        Button addButton = findViewById(R.id.addButton);
        Button updateButton = findViewById(R.id.updateButton);
        Button deleteButton = findViewById(R.id.deleteButton);

        studentListView = findViewById(R.id.studentListView);
        studentDetailsList = new ArrayList<>();
        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, studentDetailsList);
        studentListView.setAdapter(adapter);

        loadStudentList();

        addButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String rollNumber = rollNumberEditText.getText().toString().trim();
                String name = nameEditText.getText().toString().trim();
                String marks = marksEditText.getText().toString().trim();
                if (!rollNumber.isEmpty() && !name.isEmpty() && !marks.isEmpty()) {
                    boolean success = dbHelper.addStudent(rollNumber, name, marks);
                    if (success) {
                        Toast.makeText(MainActivity.this, "Student added successfully", Toast.LENGTH_SHORT).show();
                        loadStudentList();
                        clearFields();
                    } else {
                        Toast.makeText(MainActivity.this, "Failed to add student", Toast.LENGTH_SHORT).show();
                    }
                } else {
                    Toast.makeText(MainActivity.this, "Please fill all fields", Toast.LENGTH_SHORT).show();
                }
            }
        });

        // Inside MainActivity.java
        updateButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String rollNumber = rollNumberEditText.getText().toString().trim();
                String name = nameEditText.getText().toString().trim();
                String marks = marksEditText.getText().toString().trim();
                if (!rollNumber.isEmpty() && !name.isEmpty() && !marks.isEmpty()) {
                    boolean success = dbHelper.updateStudent(rollNumber, name, marks);
                    if (success) {
                        Toast.makeText(MainActivity.this, "Student updated successfully", Toast.LENGTH_SHORT).show();
                        loadStudentList();
                        clearFields();
                    } else {
                        Toast.makeText(MainActivity.this, "Failed to update student", Toast.LENGTH_SHORT).show();
                    }
                } else {
                    Toast.makeText(MainActivity.this, "Please fill all fields", Toast.LENGTH_SHORT).show();
                }
            }
        });

        deleteButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String rollNumber = rollNumberEditText.getText().toString().trim();
                if (!rollNumber.isEmpty()) {
                    boolean success = dbHelper.deleteStudent(rollNumber);
                    if (success) {
                        Toast.makeText(MainActivity.this, "Student deleted successfully", Toast.LENGTH_SHORT).show();
                        loadStudentList();
                        clearFields();
                    } else {
                        Toast.makeText(MainActivity.this, "Failed to delete student", Toast.LENGTH_SHORT).show();
                    }
                } else {
                    Toast.makeText(MainActivity.this, "Please enter roll number to delete", Toast.LENGTH_SHORT).show();
                }
            }
        });

        studentListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                String studentDetails = adapter.getItem(position);
                // You can parse the student details if needed
                Toast.makeText(MainActivity.this, "Clicked on: " + studentDetails, Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void loadStudentList() {
        studentDetailsList.clear();
        Cursor cursor = dbHelper.getAllStudents();
        if (cursor.moveToFirst()) {
            do {
                String id = cursor.getString(0);
                String rollNumber = cursor.getString(1);
                String name = cursor.getString(2);
                String marks = cursor.getString(3);
                String studentDetails = "ID: " + id + "nRoll Number: " + rollNumber + "nName: " + name + "nMarks: " + marks;
                studentDetailsList.add(studentDetails);
            } while (cursor.moveToNext());
            adapter.notifyDataSetChanged();
        } else {
            Toast.makeText(this, "No students found", Toast.LENGTH_SHORT).show();
        }
        cursor.close();
    }

    private void clearFields() {
        rollNumberEditText.setText("");
        nameEditText.setText("");
        marksEditText.setText("");
    }
}

Databasehelper.java —

package com.example.l7q1;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final String DATABASE_NAME = "student.db";
    private static final int DATABASE_VERSION = 1;

    private static final String TABLE_NAME = "student";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_ROLL_NUMBER = "roll_number";
    private static final String COLUMN_NAME = "name";
    private static final String COLUMN_MARKS = "marks";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTableQuery = "CREATE TABLE " + TABLE_NAME + " ("
                + COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, "
                + COLUMN_ROLL_NUMBER + " VARCHAR, "
                + COLUMN_NAME + " VARCHAR, "
                + COLUMN_MARKS + " VARCHAR)";
        db.execSQL(createTableQuery);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
        onCreate(db);
    }

    public boolean addStudent(String rollNumber, String name, String marks) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues contentValues = new ContentValues();
        contentValues.put(COLUMN_ROLL_NUMBER, rollNumber);
        contentValues.put(COLUMN_NAME, name);
        contentValues.put(COLUMN_MARKS, marks);
        long result = db.insert(TABLE_NAME, null, contentValues);
        return result != -1;
    }

    public Cursor getAllStudents() {
        SQLiteDatabase db = this.getWritableDatabase();
        return db.rawQuery("SELECT * FROM " + TABLE_NAME, null);
    }

    // Inside DatabaseHelper.java
    public boolean updateStudent(String rollNumber, String name, String marks) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_NAME, name);
        values.put(COLUMN_MARKS, marks);
        int affectedRows = db.update(TABLE_NAME, values, COLUMN_ROLL_NUMBER + "=?", new String[]{rollNumber});
        return affectedRows > 0;
    }


    public boolean deleteStudent(String id) {
        SQLiteDatabase db = this.getWritableDatabase();
        int deletedRows = db.delete(TABLE_NAME, "id=?", new String[]{id});
        return deletedRows > 0;
    }
}

Activity_main.xml —

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <EditText
        android:id="@+id/rollNumberEditText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Roll Number"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"/>

    <EditText
        android:id="@+id/nameEditText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Name"
        android:layout_below="@id/rollNumberEditText"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"/>

    <EditText
        android:id="@+id/marksEditText"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Marks"
        android:layout_below="@id/nameEditText"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"/>

    <Button
        android:id="@+id/addButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Add"
        android:layout_below="@id/marksEditText"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"/>

    <Button
        android:id="@+id/updateButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Update"
        android:layout_below="@id/addButton"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"/>

    <Button
        android:id="@+id/deleteButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Delete"
        android:layout_below="@id/updateButton"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"/>

    <ListView
        android:id="@+id/studentListView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/deleteButton"
        android:layout_marginTop="16dp"
        android:divider="@null"
        android:dividerHeight="0dp"/>

</RelativeLayout>

Media player
Main Activity.java

package com.example.l6q2;

import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import androidx.activity.EdgeToEdge;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;


import android.media.MediaPlayer;
import android.os.Bundle;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

    private ListView songListView;
    private MediaPlayer mediaPlayer;
    private int currentPosition = -1;

    private int[] songResources = {R.raw.song1, R.raw.song2, R.raw.song3}; // Example: raw resources of songs

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

        songListView = findViewById(R.id.songListView);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.song_titles, android.R.layout.simple_list_item_1);
        songListView.setAdapter(adapter);

        songListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                if (mediaPlayer != null && mediaPlayer.isPlaying()) {
                    mediaPlayer.stop();
                    mediaPlayer.release();
                    mediaPlayer = null;
                }
                playSong(songResources[position]);
                currentPosition = position;
            }
        });

        // Initialize media controls
        Button playButton = findViewById(R.id.playButton);
        Button pauseButton = findViewById(R.id.pauseButton);
        Button stopButton = findViewById(R.id.stopButton);

        playButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mediaPlayer != null && !mediaPlayer.isPlaying()) {
                    mediaPlayer.start();
                }
            }
        });

        pauseButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mediaPlayer != null && mediaPlayer.isPlaying()) {
                    mediaPlayer.pause();
                }
            }
        });

        stopButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mediaPlayer != null) {
                    mediaPlayer.stop();
                    mediaPlayer.release();
                    mediaPlayer = null;
                }
            }
        });
    }

    private void playSong(int songResource) {
        mediaPlayer = MediaPlayer.create(this, songResource);
        mediaPlayer.start();
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (mediaPlayer != null) {
            mediaPlayer.stop();
            mediaPlayer.release();
            mediaPlayer = null;
        }
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <ListView
        android:id="@+id/songListView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:layout_alignParentBottom="true">

        <Button
            android:id="@+id/playButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Play" />

        <Button
            android:id="@+id/pauseButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Pause" />

        <Button
            android:id="@+id/stopButton"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Stop" />

    </LinearLayout>

</RelativeLayout>

activity_player.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <!-- Media controls -->
    <Button
        android:id="@+id/playButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Play"
        android:layout_centerInParent="true"/>

    <Button
        android:id="@+id/pauseButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Pause"
        android:layout_below="@id/playButton"
        android:layout_marginTop="16dp"
        android:layout_centerHorizontal="true"/>

    <Button
        android:id="@+id/stopButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Stop"
        android:layout_below="@id/pauseButton"
        android:layout_marginTop="16dp"
        android:layout_centerHorizontal="true"/>

    <!-- SeekBar for tracking progress -->
    <SeekBar
        android:id="@+id/seekBar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/stopButton"
        android:layout_marginTop="16dp"
        android:paddingHorizontal="16dp"
        android:max="100"/>

</RelativeLayout>

I’d like to help, I recently made a Database related apps : You can go through the code and understand pretty clearly:

For studying Database in SQLite refer to the DatabaseHelper.java —

This is an example of airline ticket reservation system

BookingsActivity.java::

package com.example.myapplication;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.widget.TextView;
import androidx.appcompat.app.AppCompatActivity;


public class BookingsActivity extends AppCompatActivity {

    private DatabaseHelper databaseHelper;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_bookings);

        databaseHelper = new DatabaseHelper(this);

        SQLiteDatabase db = databaseHelper.getReadableDatabase();
        Cursor cursor = db.query(DatabaseHelper.TABLE_BOOKINGS, null, null, null, null, null, null);

        StringBuilder pastBookings = new StringBuilder();
        while (cursor.moveToNext()) {
            pastBookings.append("Date: ").append(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COLUMN_DATE)))
                    .append(", From: ").append(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COLUMN_FROM)))
                    .append(", To: ").append(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COLUMN_TO)))
                    .append(", Airline: ").append(cursor.getString(cursor.getColumnIndex(DatabaseHelper.COLUMN_AIRLINE)))
                    .append("n");
        }
        cursor.close();
        db.close();

        TextView pastBookingsTextView = findViewById(R.id.pastBookingsTextView);
        pastBookingsTextView.setText(pastBookings.toString());
    }
}

MainActivity.java::

package com.example.myapplication;

import android.content.ContentValues;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;


public class MainActivity extends AppCompatActivity {

    String[] airlines ={ "Air India", "Indigo", "Air Asia", "SpiceJet"};
    String[] places = { "Kolkata", "Mangalore", "Mumbai", "Chennai", "Delhi"};
    String[] passengerCounts = {"1", "2", "3", "4", "5"};
    String[] ticketClasses = {"Economy", "Business", "First Class"};

    private DatabaseHelper databaseHelper;
    String date;

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

        databaseHelper = new DatabaseHelper(this);

        Spinner fromSpinner = findViewById(R.id.fromSpinner);
        Spinner toSpinner = findViewById(R.id.toSpinner);
        Spinner airlineSpinner = findViewById(R.id.airlineSpinner);
        Spinner passengerSpinner = findViewById(R.id.passengerSpinner);
        Spinner classSpinner = findViewById(R.id.classSpinner);

        ArrayAdapter<String> placeAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, places);
        ArrayAdapter<String> airlineAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, airlines);
        ArrayAdapter<String> passengerAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, passengerCounts);
        ArrayAdapter<String> classAdapter = new ArrayAdapter<>(this, android.R.layout.simple_spinner_item, ticketClasses);

        fromSpinner.setAdapter(placeAdapter);
        toSpinner.setAdapter(placeAdapter);
        airlineSpinner.setAdapter(airlineAdapter);
        passengerSpinner.setAdapter(passengerAdapter);
        classSpinner.setAdapter(classAdapter);

        Button bookFlightButton = findViewById(R.id.bookFlightButton);
        bookFlightButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                bookFlight();
            }
        });
    }

    private void bookFlight() {
        String date = this.date;
        String from = ((Spinner) findViewById(R.id.fromSpinner)).getSelectedItem().toString();
        String to = ((Spinner) findViewById(R.id.toSpinner)).getSelectedItem().toString();
        String airline = ((Spinner) findViewById(R.id.airlineSpinner)).getSelectedItem().toString();
        String passengers = ((Spinner) findViewById(R.id.passengerSpinner)).getSelectedItem().toString();
        String ticketClass = ((Spinner) findViewById(R.id.classSpinner)).getSelectedItem().toString();

        SQLiteDatabase db = databaseHelper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(DatabaseHelper.COLUMN_DATE, date);
        values.put(DatabaseHelper.COLUMN_FROM, from);
        values.put(DatabaseHelper.COLUMN_TO, to);
        values.put(DatabaseHelper.COLUMN_AIRLINE, airline);
        values.put(DatabaseHelper.COLUMN_PASSENGERS, passengers);
        values.put(DatabaseHelper.COLUMN_CLASS, ticketClass);

        db.insert(DatabaseHelper.TABLE_BOOKINGS, null, values);
        db.close();

        Toast.makeText(this,"Booking successful!!",Toast.LENGTH_SHORT).show();
    }
}

DatabaseHelper.java:::

package com.example.myapplication;

        import android.content.Context;
        import android.database.sqlite.SQLiteDatabase;
        import android.database.sqlite.SQLiteOpenHelper;

public class DatabaseHelper extends SQLiteOpenHelper {
    static final String DATABASE_NAME = "airline_reservation.db";
    static final int DATABASE_VERSION = 1;
    static final String TABLE_BOOKINGS = "bookings";
    static final String COLUMN_ID = "id";
    static final String COLUMN_DATE = "date";
    static final String COLUMN_FROM = "from_location";
    static final String COLUMN_TO = "to_location";
    static final String COLUMN_AIRLINE = "airline";
    static final String COLUMN_PASSENGERS = "passengers";
    static final String COLUMN_CLASS = "class";

    // SQL statement to create the bookings table
    private static final String CREATE_TABLE_BOOKINGS = "CREATE TABLE " + TABLE_BOOKINGS +
            "(" +
            COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT," +
            COLUMN_DATE + " TEXT," +
            COLUMN_FROM + " TEXT," +
            COLUMN_TO + " TEXT," +
            COLUMN_AIRLINE + " TEXT," +
            COLUMN_PASSENGERS + " TEXT," +
            COLUMN_CLASS + " TEXT" +
            ")";

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE_BOOKINGS);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_BOOKINGS);

        // Create tables again
        onCreate(db);
    }
}

activity_bookings.xml::

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BookingsActivity">

    <TextView
        android:id="@+id/pastBookingsTextView"
        android:layout_width="378dp"
        android:layout_height="606dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

activity_main.xml::

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".BookingsActivity">

    <TextView
        android:id="@+id/pastBookingsTextView"
        android:layout_width="378dp"
        android:layout_height="606dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

Also Don’t forget to use activity tag for Intent in the AndroidManifest.xml

It should look something like this::

<activity
            android:name=".BookingsActivity"
            android:exported="false" />

If you need specifics feel free to ask, this is a very simple program which can help you learn the basics of DatabaseHelper.
Have to code dump here as Android studio is notorious for the app crashing if there is even a small error and gradle issues can be overwhelming.

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