Android SQLite CRUD - RecyclerView ContextMenu- INSERT SELECT, DELETE

October 18, 2017 Oclemy Android SQLite, Android Menu, Android RecyclerView 13 minutes, 53 seconds

This is an android tutorial of how to work with SQLite datbase and RecyclerView with ContextMenu.

We perform the following:

  1. Insert Data to SQLite Database
  2. Retrieve Data from SQLite Database and render in a RecyclerView
  3. Long press the recyclerview to show a contextmenu.
  4. Choose Delete to Delete data from SQLite database.

SQLite RecyclerView ContextMenu

SQLite RecyclerView ContextMenu

SQLite RecyclerView ContextMenu

Let's go.

1. Create Basic Activity Project

  1. First create an empty project in android studio. Go to File --> New Project.

  2. Type the application name and choose the company name. New Project Dialog

  3. Choose minimum SDK. Choose minimum SDK

  4. Choose Basic Activity. Choose Empty Activity

  5. Click Finish. Finish

Basic Activity will have a toolbar and floating action button already added in the layout

Normally two layouts get generated with this option:

No. Name Type Description
1. activity_main.xml XML Layout Will get inflated into MainActivity Layout.Typically contains appbarlayout with toolbar.Also has a floatingactionbutton.
2. content_main.xml XML Layout Will be included into activity_main.xml.You add your views and widgets here.
3. MainActivity.java Class Main Activity.

In this example I used a basic Activity.

The Activity will automatically be registered in the android_manifest.xml. Android Activities are components and normally need to be registered as an application component.

If you've created yours manually then register it inside the <application>...<application> as following, replacing the MainActivity with your Activity name:


        <activity android:name=".MainActivity">

            <intent-filter>

                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />

            </intent-filter>

        </activity>

You can see that one action and category are specified as intent filters. The category makes our MainActivity as launcher Activity. Launcher activities get executed first when th android app is run.

Advantage of Creating Basic Activity project

You can optionally choose empty Activity over basic Activity for this project.

However basic Activity has the following advantages:

No. Advantage
1. Provides us a readymade toolbar which gives us actionbar features yet easily customizable
2. Provides us with appbar layout which implements material design appbar concepts.
3. Provides a FloatinActionButton which we can readily use to initiate quick actions especially in examples like these.
4. Decouples our custom content views and widgets from the templating features like toolbar.

Generated Project Structure

AndroidStudio will generate for you a project with default configurations via a set of files and directories.

Here are the most important of them:

No. File Major Responsibility
1. build/ A directory containing resources that have been compiled from the building of application and the classes generated by android tools. Such a tool is the R.java file. R.java file normally holds the references to application resources.
2. libs/ To hold libraries we use in our project.
3. src/main/ To hold the source code of our application.This is the main folder you work with.
4. src/main/java/ Contains our java classes organized as packages.
5. src/main/res/ Contains our project resources folders as follows.
6. src/main/res/drawable/ Contains our drawable resources.
7. src/main/res/layout/ Contains our layout resources.
8. src/main/res/menu/ Contains our menu resources XML code.
9. src/main/res/values/ Contains our values resources XML code.These define sets of name-value pairs and can be strings, styles and colors.
10. AndroidManifest.xml This file gets autogenerated when we create an android project.It will define basic information needed by the android system like application name,package name,permissions,activities,intents etc.
11. build.gradle Gradle Script used to build the android app.

2. Add Dependencies

Let's add build.gradle dependencies. These are basically support library dependencies and no special third party library

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:23.3.0'
    compile 'com.android.support:design:23.3.0'
    compile 'com.android.support:cardview-v7:23.3.0'
}

3. Create User Interface

User interfaces are typically created in android using XML layouts as opposed by direct java coding.

This is an example fo declarative programming.

Advantages of Using XML over Java
No. Advantage
1. Declarative creation of widgets and views allows us to use a declarative language XML which makes is easier.
2. It's easily maintanable as the user interface is decoupled from your Java logic.
3. It's easier to share or download code and safely test them before runtime.
4. You can use XML generated tools to generate XML

Here are our layouts for this project:

(a). activity_main.xml

  • This layout gets inflated to MainActivity user interface.
  • It includes the content_main.xml.

Here are some of the widgets, views and viewgroups that get employed"

No. View/ViewGroup Package Role
1. CordinatorLayout android.support.design.widget Super-powered framelayout that provides our application's top level decoration and is also specifies interactions and behavioros of all it's children.
2. AppBarLayout android.support.design.widget A LinearLayout child that arranges its children vertically and provides material design app bar concepts like scrolling gestures.
3. ToolBar <android.support.v7.widget A ViewGroup that can provide actionbar features yet still be used within application layouts.
4. FloatingActionButton android.support.design.widget An circular imageview floating above the UI that we can use as buttons.
<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"
    android:fitsSystemWindows="true"
    tools:context="com.tutorials.hp.sqlitecontextmenudelete.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

    </android.support.design.widget.AppBarLayout>

    <include layout="@layout/content_main" />

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        android:src="@android:drawable/ic_dialog_email" />

</android.support.design.widget.CoordinatorLayout>

(b). content_main.xml

This layout gets included in your activity_main.xml. You define your UI widgets right here. In this case we add a RecyclerView as our AdapterView.

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.tutorials.hp.sqlitecontextmenudelete.MainActivity"
    tools:showIn="@layout/activity_main">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/rv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"></android.support.v7.widget.RecyclerView>
</RelativeLayout>

(c). dialog_layout.xml

This is our input dialog layout.

This layout will inflate to an input dialog that will be used as the data entry form.

<?xml version="1.0" encoding="utf-8"?>

    <android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="horizontal" android:layout_width="500dp"
        xmlns:card_view="http://schemas.android.com/apk/res-auto"
        android:layout_margin="1dp"
        card_view:cardCornerRadius="10dp"
        card_view:cardElevation="5dp"
        android:layout_height="match_parent">

    <LinearLayout
            android:layout_width="match_parent"
            android:orientation="vertical"
            android:layout_height="match_parent">

        <android.support.design.widget.TextInputLayout
            android:id="@+id/nameLayout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <EditText
                android:id="@+id/nameEditTxt"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:singleLine="true"
                android:hint= "Name" />
        </android.support.design.widget.TextInputLayout>

        <Button android:id="@+id/saveBtn"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="Save"
            android:clickable="true"
            android:background="@color/colorAccent"
            android:layout_marginTop="40dp"
            android:textColor="@android:color/white"/>
        <Button android:id="@+id/retrieveBtn"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:text="Retrieve"
            android:clickable="true"
            android:background="@color/colorAccent"
            android:layout_marginTop="40dp"
            android:textColor="@android:color/white"/>

</LinearLayout>
</android.support.v7.widget.CardView>

(d). model.xml

This is our model or template layout for each row in our recyclerview.

At the root we have a CardView.

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal" android:layout_width="match_parent"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_margin="5dp"
    card_view:cardCornerRadius="10dp"
    card_view:cardElevation="5dp"
    android:layout_height="wrap_content">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="Name"
            android:id="@+id/nameTxt"
            android:padding="10dp"
            android:layout_alignParentTop="true"
            />
    </RelativeLayout>
</android.support.v7.widget.CardView>

4. Java Classes

Here are our Java classes:

Our Data Object

This is our POJO class. Our data object.

Represents a single Planet object with several properties.

package com.tutorials.hp.sqlitecontextmenudelete.mDataObject;

public class Planet {

    String name;
    int id;

    public Planet() {
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getId() {
        return id;
    }

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

Our SQLite classes

(a). Constants.java

This is a class that represents our SQLite database Constants. These include:

  1. Database name
  2. database version
  3. Table Name
  4. Column Names.
  5. SQLite Table-Creation and Table-Deletion statement.
package com.tutorials.hp.sqlitecontextmenudelete.mDataBase;

public class Constants {
    //COLUMNS
    static final String ROW_ID="id";
    static final String NAME="name";

    //DB PROPS
    static final String DB_NAME="ff_DB";
    static final String TB_NAME="ff_TB";
    static final int DB_VERSION=1;

    //CREATE TB
    static final String CREATE_TB="CREATE TABLE ff_TB(id INTEGER PRIMARY KEY AUTOINCREMENT,"
            + "name TEXT NOT NULL);";

    //TABLE DROP STMT
    static final String DROP_TB="DROP TABLE IF EXISTS "+TB_NAME;

}

(c). DBHelper.java

This is our SQlite database helper class.

This class derives from SQLiteOpenHelper class.

This class is responsible for two tasks:

  1. Creating Database Table
  2. Upgrading Database Table
package com.tutorials.hp.sqlitecontextmenudelete.mDataBase;

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

public class DBHelper extends SQLiteOpenHelper {

    public DBHelper(Context context) {
        super(context, Constants.DB_NAME, null, Constants.DB_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        try
        {
            db.execSQL(Constants.CREATE_TB);
        }catch (SQLException e)
        {
            e.printStackTrace();
        }

    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL(Constants.DROP_TB);
        onCreate(db);
    }
}

(c). DBAdapter.java

This is our SQLite database Adapter class.

This class is responsible for:

  1. Opening Database Connection.
  2. Closing Database Connection.
  3. Inserting Data to SQLite Database.
  4. Retrieving Data from SQlite database.
  5. Deletion of data from SQLite Database.
package com.tutorials.hp.sqlitecontextmenudelete.mDataBase;

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

public class DBAdapter {
    Context c;
    SQLiteDatabase db;
    DBHelper helper;

    public DBAdapter(Context c) {
        this.c = c;
        helper=new DBHelper(c);
    }

    //OPEN
    public void openDB()
    {
        try
        {
           db=helper.getWritableDatabase();
        }catch (SQLException e)
        {
            e.printStackTrace();
        }
    }

    //CLOSE DB
    public void closeDB()
    {
        try
        {
            helper.close();
        }catch (SQLException e)
        {
            e.printStackTrace();
        }
    }

    //INSERT/SAVE
    public boolean add(String name)
    {
        try
        {
            ContentValues cv=new ContentValues();
            cv.put(Constants.NAME, name);

            db.insert(Constants.TB_NAME, Constants.ROW_ID, cv);

           return true;

        }catch (SQLException e)
        {
            e.printStackTrace();
        }

        return false;
    }

    //RETRIEVE
    public Cursor retrieve()
    {
        String[] columns={Constants.ROW_ID,Constants.NAME};

        return db.query(Constants.TB_NAME,columns,null,null,null,null,null);
    }

    //DELETE/REMOVE
    public boolean delete(int id)
    {
        try
        {
            int result=db.delete(Constants.TB_NAME,Constants.ROW_ID+" =?",new String[]{String.valueOf(id)});

            if(result>0)
            {
                return true;
            }

        }catch (SQLException e)
        {
            e.printStackTrace();
        }

        return false;
    }
}

Our RecyclerView classes

(a). MyLongClickListener.java

Our RecyclerView viewitems long click listener interface

package com.tutorials.hp.sqlitecontextmenudelete.mRecycler;

public interface MyLongClickListener {

    void onLongClick(int pos);

}

(b). MyHolder.java

Our RecyclerView.ViewHolder class.

package com.tutorials.hp.sqlitecontextmenudelete.mRecycler;

import android.support.v7.widget.RecyclerView;
import android.view.ContextMenu;
import android.view.View;
import android.widget.TextView;

import com.tutorials.hp.sqlitecontextmenudelete.R;

public class MyHolder extends RecyclerView.ViewHolder implements View.OnLongClickListener,View.OnCreateContextMenuListener {

    TextView nameTxt;
    MyLongClickListener longClickListener;

    public MyHolder(View itemView) {
        super(itemView);

        this.nameTxt= (TextView) itemView.findViewById(R.id.nameTxt);

        itemView.setOnLongClickListener(this);
        itemView.setOnCreateContextMenuListener(this);
    }

    public void setLongClickListener(MyLongClickListener longClickListener)
    {
        this.longClickListener=longClickListener;
    }

    @Override
    public boolean onLongClick(View v) {
        this.longClickListener.onLongClick(getLayoutPosition());
        return false;
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {

        //OUR CONTEXT MENU
        menu.setHeaderTitle("ACTION : ");
        menu.add(0,0,0,"New");
        menu.add(0,1,0,"Delete");

    }
}

(c). MyAdapter.java

Our RecyclerView Adapter class. Will inflate our model.xml layout into a view objects and bind data from the sqlite database to them.

package com.tutorials.hp.sqlitecontextmenudelete.mRecycler;

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.Toast;

import com.tutorials.hp.sqlitecontextmenudelete.R;
import com.tutorials.hp.sqlitecontextmenudelete.mDataBase.DBAdapter;
import com.tutorials.hp.sqlitecontextmenudelete.mDataObject.Planet;

import java.util.ArrayList;

public class MyAdapter extends RecyclerView.Adapter<MyHolder> {

    Context c;
    ArrayList<Planet> planets;
    int selectedPos;

    public MyAdapter(Context c, ArrayList<Planet> planets) {
        this.c = c;
        this.planets = planets;
    }

    @Override
    public MyHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v= LayoutInflater.from(parent.getContext()).inflate(R.layout.model,parent,false);
        MyHolder holder=new MyHolder(v);
        return holder;
    }

    @Override
    public void onBindViewHolder(MyHolder holder, int position) {
         holder.nameTxt.setText(planets.get(position).getName());

        holder.setLongClickListener(new MyLongClickListener() {
            @Override
            public void onLongClick(int pos) {
                selectedPos=pos;
            }
        });
    }

    @Override
    public int getItemCount() {
        return planets.size();
    }

    //DELETE PLANET
    public void deletePlanet()
    {
        //GET ID
        Planet p=planets.get(selectedPos);
        int id=p.getId();

        //DELETE IT FROM DB
        DBAdapter db=new DBAdapter(c);
        db.openDB();
        if(db.delete(id))
        {
            //DELETE ALSO FROM ARRAYLIST
            planets.remove(selectedPos);
        }else {
            Toast.makeText(c,"Unable To Delete",Toast.LENGTH_SHORT).show();
        }

        db.closeDB();

        this.notifyItemRemoved(selectedPos);
    }

}

Our Activity class

MainActivity.java

This is our main activity. It represents our UI screen.

Our UI will comprise of a RecyclerView with data items from SQLite database.

It will also host a dialog which will act as our data entry form.

package com.tutorials.hp.sqlitecontextmenudelete;

import android.app.Dialog;
import android.database.Cursor;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.Toolbar;
import android.view.View;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.tutorials.hp.sqlitecontextmenudelete.mDataBase.DBAdapter;
import com.tutorials.hp.sqlitecontextmenudelete.mDataObject.Planet;
import com.tutorials.hp.sqlitecontextmenudelete.mRecycler.MyAdapter;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    RecyclerView rv;
    MyAdapter adapter;
    EditText nameEditText;
    Button saveBtn,retrieveBtn;
    ArrayList<Planet> planets=new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);

        rv= (RecyclerView) findViewById(R.id.rv);
        rv.setLayoutManager(new LinearLayoutManager(this));

        adapter=new MyAdapter(this,planets);

        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                displayDialog();
            }
        });
    }

    private void displayDialog()
    {
        Dialog d=new Dialog(this);
        d.setTitle("SQLite Database");
        d.setContentView(R.layout.dialog_layout);

        nameEditText= (EditText) d.findViewById(R.id.nameEditTxt);
        saveBtn= (Button) d.findViewById(R.id.saveBtn);
        retrieveBtn= (Button) d.findViewById(R.id.retrieveBtn);

        saveBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               save(nameEditText.getText().toString());
            }
        });
        retrieveBtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                getPlanets();
            }
        });

        d.show();
    }

    private void save(String name)
    {
        DBAdapter db=new DBAdapter(this);
        db.openDB();
        if(db.add(name))
        {
            nameEditText.setText("");
        }else
        {
            Toast.makeText(this,"Unable To Save",Toast.LENGTH_SHORT).show();
        }

        db.closeDB();

        //REFRESH
        getPlanets();
    }

    private void getPlanets()
    {
        planets.clear();

        DBAdapter db=new DBAdapter(this);
        db.openDB();
        Planet p=null;
        Cursor c=db.retrieve();

        while (c.moveToNext())
        {
            int id=c.getInt(0);
            String name=c.getString(1);

            p=new Planet();
            p.setId(id);
            p.setName(name);

            planets.add(p);
        }

        db.closeDB();

        if(planets.size()>0)
        {
            rv.setAdapter(adapter);
        }
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        if(item.getTitle()=="New")
        {
            displayDialog();
        }else if(item.getTitle()=="Delete")
        {
            adapter.deletePlanet();
        }
        return super.onContextItemSelected(item);
    }
}

Comments