Android Room Persistence Library Example

Room Persistence Library

Major problem with SQLite usage is

There is no compile-time verification of raw SQL queries.For example if you write a SQL query with a wrong column name that does not exist in real database then it will give exception during run time and you can not capture this issue during compile time.

As your schema changes you need to update the affected SQL queries manually. This process can be time consuming and error prone.

You need to use lots of boilerplate code to convert between SQL queries and Java data objects.

Room takes care of these concerns for you while providing an abstraction layer over SQLite.

By creating an event app i will demonstrate you the working of insert, update, delete and retrieve functionality using the Room database.Get GITHUB code from HERE.

There are three major components in Room:

Entity : A class annotated with the @Entity annotation is mapped to a table in database. Every entity is persisted in its own table and every field in class represents the column name.

tableName attribute is used to define the name of the table
Every entity class must have at-least one Primary Key field, annotated with @PrimaryKey
Fields in entity class can be annotated with @ColumnInfo(name = “name_of_column”) annotation to give specific column names

DAO : Data Access Object is either be an interface or an abstract class annotated with @Doa annotation, containing all the methods to define the operations to be performed on data. The methods can be annotated with

@Query to retrieve data from database
@Insert to insert data into database
@Delete to delete data from database
@Update to update data in database

Note:The result of SQLite queries are composed into cursor object, DAO methods abstract the conversion of cursor to Entity objects and vice-versa.

Database : Database is a container for tables. An abstract class annotated with @Database annotation is used to create a database with given name along with database version.

version = intValueForDBVersion is used to define the database version
entities = {EntityClassOne.class, ….} is used to define list of entities for database

Building an Event App

We will build a Event App that will allow the user to:

Create and Save event in database
Display a list of events
Update and Delete event

Creating New Project

1.In Android Studio, go to File ⇒ New Project and fill all the details required to create a new project. When it prompts to select a default activity, select Blank Activity and proceed.

2.Open build.gradle (Module:app) and add room library dependency.

dependencies {
   
    implementation 'com.android.support:support-v4:26.1.0'
    compile 'com.android.support:design:26.1.0'

    //room dependency
    compile 'android.arch.persistence.room:runtime:1.0.0'
    annotationProcessor 'android.arch.persistence.room:compiler:1.0.0'

    //recyclerview dependency
    compile 'com.android.support:recyclerview-v7:26.1.0'
    
}

Create Entity

3. Before creating a database, Let’s create an Entity, named as Event and later, Objects of this class will be added to database.

To do this:

Create a class named Event.
Add @Entity annotation on the class.
Add ID, title,description and date fields.
Important: mark at least one field with @PrimaryKey annotation.
Use alt+insert to implement constructor, override getter and setter, and optionally override equals or toString.

Event.Java

package com.example.lenovo.eventapp.entity;

import android.arch.persistence.room.Entity;
import android.arch.persistence.room.Ignore;
import android.arch.persistence.room.PrimaryKey;

import static com.example.lenovo.eventapp.entity.Event.TABLE_NAME;


@Entity(tableName = TABLE_NAME)
public class Event {


    public static final String TABLE_NAME = "events";


    @PrimaryKey(autoGenerate = true)
    private int id;
    private String title;
    private String description;
    private String date;

    public Event() {

    }

    @Ignore
    public Event(int id, String title, String description) {
        this.id = id;
        this.title = title;
        this.description = description;
        this.date = date;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getDescription() {
        return description;
    }

    public String getTitle() {
        return title;
    }


    @Override
    public String toString() {
        return "Event{" +
                "id=" + id +
                ", name='" + title + '\'' +
                ", description='" + description + '\'' +
                ", date='" + date + '\'' +
                '}';
    }

}

Creating DAO

4. DAOs define all methods to access database, annotated with @Dao annotation. The DAO perform CRUD operations on data within a database.

The following code will:

Create an interface, marked with @Dao annotation.
Add methods for CRUD operations.

EventDao.Java

package com.example.lenovo.eventapp.dao;

import android.arch.persistence.room.Dao;
import android.arch.persistence.room.Delete;
import android.arch.persistence.room.Insert;
import android.arch.persistence.room.Query;
import android.arch.persistence.room.Update;

import com.example.lenovo.eventapp.entity.Event;

import java.util.List;


@Dao
public interface EventDao {

    @Query("SELECT * FROM " + Event.TABLE_NAME )
    List<Event> getEvents();

    @Insert
    void addEvent(Event event);

    @Delete
    void deleteEvent(Event event);

    @Update
    void updateEvent(Event event);

}

Create Database

5. Now, we have table defined as Entity and CRUD methods defined via EventDao.

We will have to:

Create an abstract class EventDatabse which extends RoomDatabase.
Add version and entities to database as @Database(entities = {Event.class}, version = 1).
Add abstract methods of all DAO’s where the returned DAO object will be constructed by Room for database interactions.

Some things to remember:

Version number is changed to update the database structure, when required in future updates
The database file name must end with the .db extension
Creating instance of database is quite costly so we will apply a Singleton Pattern to create and use already instantiated single instance for every database access.

EventDatabase.Java

package com.example.lenovo.eventapp.db;

import android.arch.persistence.room.Database;
import android.arch.persistence.room.Room;
import android.arch.persistence.room.RoomDatabase;
import android.content.Context;

import com.example.lenovo.eventapp.dao.EventDao;
import com.example.lenovo.eventapp.entity.Event;


@Database(entities = {Event.class},version = 1)
public abstract class EventDatabase extends RoomDatabase{
        private static final String DB_NAME = "Event_Database.db";
        private static EventDatabase INSTANCE;
        public abstract EventDao eventDao();

        public static EventDatabase getEventDatabase(Context context) {
                if (INSTANCE == null) {
                        INSTANCE = Room.databaseBuilder(context, EventDatabase.class, DB_NAME).build();

                }
                return INSTANCE;
        }


}

Note: It is good to note that Room does not allow code execution on Main thread. Instead, allowMainThreadQueries is used to allow the execution. However, using this is not recommended on real apps. You must perform queries on AsyncTask (or handler, rxjava), otherwise your application will crash or cause ANR problems.

Implement Database Interactions

6. The below snippet will demonstrate the working of insert, update, and delete functionality using the Room database.

Add Event

private static final String DB_NAME = "Event_Database.db";
private static EventDatabase INSTANCE;
public abstract class EventDatabase extends RoomDatabase{
        private static final String DB_NAME = "Event_Database.db";
        private static EventDatabase INSTANCE;
        public abstract EventDao eventDao();

        public static EventDatabase getEventDatabase(Context context) {
                if (INSTANCE == null) {
                        INSTANCE = Room.databaseBuilder(context, EventDatabase.class, DB_NAME).build();

                }
                return INSTANCE;
        }


}
//add event into the database
EventDatabase.getEventDatabase(getApplicationContext()).eventDao().addEvent(event);

Retrieve And Display EventList

private static final String DB_NAME = "Event_Database.db";
private static EventDatabase INSTANCE;

public abstract class EventDatabase extends RoomDatabase{
        private static final String DB_NAME = "Event_Database.db";
        private static EventDatabase INSTANCE;
        public abstract EventDao eventDao();

        public static EventDatabase getEventDatabase(Context context) {
                if (INSTANCE == null) {
                        INSTANCE = Room.databaseBuilder(context, EventDatabase.class, DB_NAME).build();

                }
                return INSTANCE;
        }


}
//get events from database
List<Event> events = EventDatabase.getEventDatabase(getApplicationContext()).eventDao().getEvents();
adapter = new EventsAdapter(events, getApplicationContext());

recyclerView.setAdapter(adapter);

Update Event

private static final String DB_NAME = "Event_Database.db";
private static EventDatabase INSTANCE;

public abstract class EventDatabase extends RoomDatabase{
        private static final String DB_NAME = "Event_Database.db";
        private static EventDatabase INSTANCE;
        public abstract EventDao eventDao();

        public static EventDatabase getEventDatabase(Context context) {
                if (INSTANCE == null) {
                        INSTANCE = Room.databaseBuilder(context, EventDatabase.class, DB_NAME).build();

                }
                return INSTANCE;
        }


}
//update event into the database
EventDatabase.getEventDatabase(getApplicationContext()).eventDao().updateEvent(event);

Delete Event

private static final String DB_NAME = "Event_Database.db";
private static EventDatabase INSTANCE;
public abstract class EventDatabase extends RoomDatabase{
        private static final String DB_NAME = "Event_Database.db";
        private static EventDatabase INSTANCE;
        public abstract EventDao eventDao();

        public static EventDatabase getEventDatabase(Context context) {
                if (INSTANCE == null) {
                        INSTANCE = Room.databaseBuilder(context, EventDatabase.class, DB_NAME).build();

                }
                return INSTANCE;
        }


}
//delete event from database
EventDatabase.getEventDatabase(getApplicationContext()).eventDao().deleteEvent(event);

7. Open activity_main.xml and write the below code .It consist of

Recyclerview : Shows list of events.

Textview : Which shows no event found text when list contains no item.

FloatingButton : When we click on it ,It opens alertdialog to add event into the database.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.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=".MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view_list_events"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent">

    </android.support.v7.widget.RecyclerView>

    <TextView
        android:id="@+id/tv_no_events_found"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:fontFamily="sans-serif"
        android:gravity="center"
        android:text="NO EVENTS FOUND!"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="25sp"
        android:visibility="gone" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab_add"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="16dp"
        android:layout_marginRight="16dp"
        app:elevation="4dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:srcCompat="@drawable/ic_add_black_24dp" />
</android.support.constraint.ConstraintLayout>

8. Open event_dialog.xml and write the below code.On update and add event I have set event_dialog.xml view to alertdialog.

event_dialog.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="8dp">

    <TextView
        android:id="@+id/dialog_title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"
        android:fontFamily="sans-serif-medium"
        android:text="New Event"
        android:textColor="@color/colorAccent"
        android:textSize="22sp"
        android:textStyle="normal" />

    <EditText
        android:id="@+id/edt_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/transparent"
        android:fontFamily="sans-serif"
        android:gravity="top"
        android:hint="Title"
        android:inputType="textCapSentences|textMultiLine"
        android:lines="2"
        android:textColor="@android:color/black"
        android:textColorHint="@color/colorPrimaryDark"
        android:textSize="18sp" />

    <EditText
        android:id="@+id/edt_discription"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@android:color/transparent"
        android:fontFamily="sans-serif"
        android:gravity="top"
        android:hint="Discription"
        android:inputType="textCapSentences|textMultiLine"
        android:lines="3"
        android:textColor="@android:color/black"
        android:textColorHint="@color/colorPrimaryDark"
        android:textSize="18sp" />

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <TextView
            android:id="@+id/tv_date"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:layout_marginLeft="8dp"
            android:fontFamily="sans-serif"
            android:textColor="@android:color/black"
            android:textSize="18sp" />

        <Button
            android:id="@+id/btn_setdate"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:background="@color/colorAccent"
            android:text="set"
            android:textColor="@android:color/white"
            android:textStyle="bold" />

    </RelativeLayout>
</LinearLayout>

9. list_item_event.xml represents the single list item of recyclerview.

list_item_event.xml

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

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:orientation="vertical">

        <TextView
            android:id="@+id/tv_title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:fontFamily="sans-serif"
            android:textColor="@android:color/holo_orange_dark"
            android:textSize="20dp"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/tv_discription"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="6dp"
            android:fontFamily="sans-serif"
            android:textColor="@android:color/holo_green_light"
            android:textSize="20dp" />
    </LinearLayout>


    <TextView
        android:id="@+id/tv_timestamp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:fontFamily="sans-serif"
        android:textColor="@color/colorAccent"
        android:textSize="20dp"
        android:textStyle="bold" />


</RelativeLayout>

10. Creating adapter class for recyclerview, open EventsAdapter.Java and write the below code.

EventsAdapter.Java

package com.example.lenovo.eventapp;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.example.lenovo.eventapp.entity.Event;

import java.util.List;


public class EventsAdapter extends RecyclerView.Adapter<EventsAdapter.EventViewHolder> {
    private final Context context;
    private List<Event> items;


    public EventsAdapter(List<Event> items, Context context) {
        this.items = items;
        this.context = context;

    }

    public class EventViewHolder extends RecyclerView.ViewHolder {
        TextView titleTextView;
        TextView dateTextView;
        TextView descriptionTextView;

        EventViewHolder(View v) {
            super(v);
            titleTextView = (TextView) v.findViewById(R.id.tv_title);
            dateTextView = (TextView) v.findViewById(R.id.tv_timestamp);
            descriptionTextView = (TextView) v.findViewById(R.id.tv_discription);

        }
    }

    @Override
    public EventViewHolder onCreateViewHolder(ViewGroup parent,
                                              int viewType) {
        View v = LayoutInflater.from(context)
                .inflate(R.layout.list_item_event, parent, false);

        return new EventViewHolder(v);
    }

    @Override
    public void onBindViewHolder(EventViewHolder holder, int position) {
        Event item = items.get(position);
        holder.titleTextView.setText(item.getTitle());
        holder.descriptionTextView.setText(item.getDescription());
        holder.dateTextView.setText(item.getDate());
    }


    @Override
    public int getItemCount() {

        return items.size();
    }


}

11. Open RecyclerTouchListener.Java and write the below code in which I have created custom onClickListener for recyclerview single item click.

RecyclerTouchListener.Java

package com.example.lenovo.eventapp;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.GestureDetector;
import android.view.MotionEvent;
import android.view.View;


public class RecyclerTouchListener implements RecyclerView.OnItemTouchListener {

    private ClickListener clicklistener;
    private GestureDetector gestureDetector;

    public RecyclerTouchListener(Context context, final RecyclerView recycleView, final ClickListener clicklistener) {

        this.clicklistener = clicklistener;
        gestureDetector = new GestureDetector(context, new GestureDetector.SimpleOnGestureListener() {
            @Override
            public boolean onSingleTapUp(MotionEvent e) {
                return true;
            }

            @Override
            public void onLongPress(MotionEvent e) {
                View child = recycleView.findChildViewUnder(e.getX(), e.getY());
                if (child != null && clicklistener != null) {
                    clicklistener.onLongClick(child, recycleView.getChildAdapterPosition(child));
                }
            }
        });
    }

    @Override
    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
        View child = rv.findChildViewUnder(e.getX(), e.getY());
        if (child != null && clicklistener != null && gestureDetector.onTouchEvent(e)) {
            clicklistener.onClick(child, rv.getChildAdapterPosition(child));
        }

        return false;
    }

    @Override
    public void onTouchEvent(RecyclerView rv, MotionEvent e) {

    }

    @Override
    public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {

    }

    public interface ClickListener {
        void onClick(View view, int position);

        void onLongClick(View view, int position);
    }
}

12. Open MainActivity.Java and write the below code.The below snippet will demonstrate the working of insert, update, delete and retrieve list of events functionality using the Room database in DatabaseAsync worker thread.

MainActivity.Java

package com.example.lenovo.eventapp;

import android.app.AlertDialog;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.content.DialogInterface;
import android.os.AsyncTask;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.app.DialogFragment;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.text.TextUtils;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import com.example.lenovo.eventapp.db.EventDatabase;
import com.example.lenovo.eventapp.entity.Event;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;


public class MainActivity extends AppCompatActivity {

    RecyclerView recyclerView;
    TextView noEventsFound;
    FloatingActionButton fab;
    EventsAdapter adapter;
    List<Event> events = new ArrayList<>();
    private static TextView tv_date;

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

        noEventsFound = (TextView) findViewById(R.id.tv_no_events_found);

        recyclerView = (RecyclerView) findViewById(R.id.recycler_view_list_events);

        recyclerView.setItemAnimator(new DefaultItemAnimator());

        recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext(), LinearLayoutManager.VERTICAL, false));

        //show list of events if exists in database
        new DatabaseAsync().execute(null, -1, null, null, null);

        //shows NO EVENTS FOUND when list is empty
        checkListEmptyOrNot();

        recyclerView.addOnItemTouchListener(new RecyclerTouchListener(getApplicationContext(), recyclerView, new RecyclerTouchListener.ClickListener() {
            @Override
            public void onClick(View view, int position) {

            }

            @Override
            public void onLongClick(View view, int position) {

                //show Alertdialog to edit or update the event
                showActionsDialog(position);
            }
        }));

        //add listener on FloatingActionButton to add event
        fab = (FloatingActionButton) findViewById(R.id.fab_add);

        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //adding  new event
                showEventDialog(false, null, -1);
            }
        });
    }

    private class DatabaseAsync extends AsyncTask<Object, Void, List<Event>> {

        @Override
        protected void onPreExecute() {
            super.onPreExecute();

            //Perform pre-adding operation here.
        }

        @Override
        protected List<Event> doInBackground(Object... params) {

            Boolean shouldUpdate = (Boolean) params[0];
            int position = (int) params[1];
            String title = (String) params[2];
            String detail = (String) params[3];
            String date = (String) params[4];

            //check whether to add add or update event
            if (shouldUpdate != null) {
                //update event
                if (shouldUpdate) {
                    Event event = events.get(position);
                    event.setTitle(title);
                    event.setDescription(detail);
                    event.setDate(date);

                    //update event into the database
                    EventDatabase.getEventDatabase(getApplicationContext()).eventDao().updateEvent(event);

                } else {
                    //add event
                    Event event = new Event();
                    event.setTitle(title);
                    event.setDescription(detail);
                    event.setDate(date);

                    //add event into the database
                    EventDatabase.getEventDatabase(getApplicationContext()).eventDao().addEvent(event);
                }

            } else {
                //delete event
                if (position != -1) {
                    Event event = events.get(position);

                    //delete event from database
                    EventDatabase.getEventDatabase(getApplicationContext()).eventDao().deleteEvent(event);
                }
            }

            //get events from database
            List<Event> events = EventDatabase.getEventDatabase(getApplicationContext()).eventDao().getEvents();
            return events;

        }

        @Override
        protected void onPostExecute(List<Event> items) {

//get list of events from doInBackground()
            events = items;

            adapter = new EventsAdapter(events, getApplicationContext());

            recyclerView.setAdapter(adapter);

            //shows NO EVENTS FOUND when list is empty
            checkListEmptyOrNot();
        }
    }

    private void showActionsDialog(final int position) {
        CharSequence colors[] = new CharSequence[]{"Edit", "Delete"};

        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setTitle("Choose option");
        builder.setItems(colors, new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                if (which == 0) {

                    //show Alertdialog to update the event
                    showEventDialog(true, events.get(position), position);
                } else {

                    //delete event from database
                    deleteEvent(position);
                }
            }
        });
        builder.show();
    }

    private void deleteEvent(int position) {

        new DatabaseAsync().execute(null, position, null, null, null);
    }

    private void showEventDialog(final Boolean shouldUpdate, final Event event, final int position) {

        LayoutInflater layoutInflater = LayoutInflater.from(getApplicationContext());
        View view = layoutInflater.inflate(R.layout.event_dialog, null);

        AlertDialog.Builder alertDialogBuilderUserInput = new AlertDialog.Builder(this);
        alertDialogBuilderUserInput.setView(view);

        TextView dialog_title = (TextView) view.findViewById(R.id.dialog_title);

        final EditText edt_title = (EditText) view.findViewById(R.id.edt_title);

        final EditText edt_discription = (EditText) view.findViewById(R.id.edt_discription);

        tv_date = (TextView) view.findViewById(R.id.tv_date);

        Button btn_setdate = (Button) view.findViewById(R.id.btn_setdate);

        //add listener to button to open datepickerdialog
        btn_setdate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                //open datepickerdialog
                showDateDialog();
            }
        });

        dialog_title.setText(!shouldUpdate ? "New Event" : "Edit Event");

        //in case of update we want all the
        //fields  to be set bydefault with text
        if (shouldUpdate && event != null) {
            edt_title.setText(event.getTitle());
            edt_discription.setText(event.getDescription());
            tv_date.setText(event.getDate());
        }

        alertDialogBuilderUserInput
                .setCancelable(false)
                .setPositiveButton(shouldUpdate ? "update" : "add", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialogBox, int id) {

                    }
                })
                .setNegativeButton("cancel",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialogBox, int id) {
                                dialogBox.cancel();
                            }
                        });

        final AlertDialog alertDialog = alertDialogBuilderUserInput.create();

        alertDialog.show();

        alertDialog.getButton(AlertDialog.BUTTON_POSITIVE).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

               // Show toast message when no text is entered
                if (TextUtils.isEmpty(edt_title.getText().toString()) && !TextUtils.isEmpty(edt_discription.getText().toString())) {
                    Toast.makeText(MainActivity.this, "Enter title!", Toast.LENGTH_SHORT).show();
                }
                else if (!TextUtils.isEmpty(edt_title.getText().toString()) && TextUtils.isEmpty(edt_discription.getText().toString())) {
                    Toast.makeText(MainActivity.this, "Enter description!", Toast.LENGTH_SHORT).show();
                }
                else if (TextUtils.isEmpty(edt_title.getText().toString()) && TextUtils.isEmpty(edt_discription.getText().toString())) {
                    Toast.makeText(MainActivity.this, "Enter title and description!", Toast.LENGTH_SHORT).show();
                }
                else {
                    alertDialog.dismiss();
                }

                //Update or add data into the database only when both field are  filled(i.e title,description)
                if (!TextUtils.isEmpty(edt_title.getText().toString()) && !TextUtils.isEmpty(edt_discription.getText().toString())) {

                    // check if user updating note

                    if (shouldUpdate && event != null) {
                        // update event
                        new DatabaseAsync().execute(shouldUpdate, position, edt_title.getText().toString(), edt_discription.getText().toString(), tv_date.getText().toString());


                    } else {
                        // create new event
                        new DatabaseAsync().execute(shouldUpdate, -1, edt_title.getText().toString(), edt_discription.getText().toString(), tv_date.getText().toString());


                    }
                }
            }
        });


    }

    public static class DatePickerFragment extends DialogFragment implements DatePickerDialog.OnDateSetListener {

        @Override
        public Dialog onCreateDialog(Bundle savedInstanceState) {
            final Calendar c = Calendar.getInstance();
            int year = c.get(Calendar.YEAR);
            int month = c.get(Calendar.MONTH);
            int day = c.get(Calendar.DAY_OF_MONTH);

            return new DatePickerDialog(getActivity(), this, year, month, day);
        }

        public void onDateSet(DatePicker view, int year, int month, int day) {
            String monthVal, dayVal = "" + day;
            if ((month + 1) < 10) {
                month += 1;
                monthVal = "0" + month;
            } else {
                month += 1;
                monthVal = "" + month;
            }
            if (day < 10) {
                dayVal = "0" + day;
            }
            SimpleDateFormat simpledateformat = new SimpleDateFormat("EEEE");
            Date date = new Date(year, month, day - 3);
            String dayOfWeek = simpledateformat.format(date);


            tv_date.setText(dayOfWeek + "\n" + dayVal + "-" + monthVal + "-" + year);

        }
    }

    private void showDateDialog() {
        DialogFragment newFragment = new DatePickerFragment();
        newFragment.show(getSupportFragmentManager(), "datePicker");
    }

    public void checkListEmptyOrNot() {
        if (events.isEmpty())
            noEventsFound.setVisibility(View.VISIBLE);
        else
            noEventsFound.setVisibility(View.GONE);
    }
}

2 thoughts on “Android Room Persistence Library Example”

Kenyx
August 20, 2018 at 5:28 am

Can’t seem to delete any entries.

1. Arun Chandravanshi
  August 20, 2018 at 8:50 am
  
  Long press on the item you will get the edit and delete option , on tap of the delete item will be deleted from the db and list.

Android Room Persistence Library Example

Room Persistence Library

Building an Event App

Creating New Project

Create Entity

Creating DAO

Create Database

Implement Database Interactions

Like this:

Related

2 thoughts on “Android Room Persistence Library Example”

Leave a ReplyCancel reply

Room Persistence Library

Building an Event App

Creating New Project

Create Entity

Creating DAO

Create Database

Implement Database Interactions

Share this:

Like this:

Related

2 thoughts on “Android Room Persistence Library Example”

Leave a ReplyCancel reply