Option 1

In the AndroidManifest.xml add ‘screenOrientation’ property in activity tag

<activity 
    - - - - - - - 
    - - - - - - -    
    android:screenOrientation="portrait" />

Option 2

In the onCreate function add the following line of code before setContentView() function

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

        //------

    }

Android Retrofit 2.1  HTTP client :

In this example i have divided in to 5 steps :

1. Add gradle dependency

2. Create models for accessing the final data (in this example, the api response json converting to java object this object class is called model )

3. Create interface to define api end point

4. Create a service class for interacting our java code with retrofit.

5. Make the api calls wherever you required

1. Add Gradle dependency (ref: http://square.github.io/retrofit/ )

compile 'com.squareup.retrofit2:retrofit:2.1.0'
compile 'com.squareup.retrofit2:converter-gson:2.1.0'

2. Create models 

User.java

public class User {
    public int id;
    public String name;
    public String email;
    public String phone;
}

3. Create interface

ApiInterface.java

import java.util.List;

import retrofit2.Call;
import retrofit2.http.Body;
import retrofit2.http.GET;
import retrofit2.http.POST;
import retrofit2.http.Path;
import retrofit2.http.Query;
import samples.bm.com.firebaselogin2.models.User;

public interface ApiInterface {

    @GET("get/users")
    Call<List<User>> getAllUsers(); //List<User> is the response from api

    @GET("get/user")
    Call<User> getUser( @Query("id") int id); //using query param (get/user?id=17479666). User is the response from the api

    //@GET("get/user/{id}")
    //Call<User> getUser( @Query("id") int id); //using path param (get/user/17479666)

    @POST("register/user")
    Call<User> registerUser(@Body User user);

    @FormUrlEncoded
    @POST("update/{id}/user")
    Call<User> updateUser(@Field("name") String name, @Field("phone") String phone, @Path("id") String id);

}

expected api response

get/users

[
    {
	"id": 17479666,
	"name": "name1",
	"email": "name1@domain.com",
	"phone": "3435353535434"
    }, 
    {
	"id": 17479668,
	"name": "name3",
	"email": "name3@domain.com",
	"phone": "3435353343434"
    }
]

get/user

{
    "id": 17479666,
    "name": "name1",
    "email": "name1@domain.com",
    "phone": "3435353535434"
}

4. Create a service class

ApiService.java

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;

import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class ApiService {

    private static ApiInterface service;
    private static String BASE_URL = "https://api.domain.com/"; //your api domain

    public static ApiInterface getInstance() {

        if (service == null) {

            Gson gson = new GsonBuilder()
                    .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
                    .create();

            Retrofit retrofit = new Retrofit.Builder()
                    .baseUrl(BASE_URL)
                    .addConverterFactory(GsonConverterFactory.create(gson))
                    .build();

            service = retrofit.create(ApiInterface.class);
        }

        return service;
    }
}

5. Make the api calls

Retrofit supports synchronous and asynchronous request execution.

 Asynchronous Requests

GET calls

ApiService.getInstance().getAllUsers().enqueue(new Callback<List<User>>() {
    @Override
    public void onResponse(Call<List<User>> call, Response<List<User>> response) {
        //api success
        List<User> users = response.body();
    }

    @Override
    public void onFailure(Call<List<User>> call, Throwable t) {
        Log.e("Apicall", t.getMessage());
    }
});

GET call with query string/param OR GET call with path string/param

int id=17479666;
ApiService.getInstance().getUser(id).enqueue(new Callback<User>() {
    @Override
    public void onResponse(Call<User> call, Response<User> response) {
        //api success
        User user = response.body();
    }

    @Override
    public void onFailure(Call<User> call, Throwable t) {
        Log.e("Apicall", t.getMessage());
    }
});

Post call

POST call with body param

User user = new User("samoe", "some@ss.com", "234242424");

ApiService.getInstance().registerUser(user).enqueue(new Callback<User>() {
    @Override
    public void onResponse(Call<User> call, Response<User> response) {
        //api success
        User user = response.body();
    }

    @Override
    public void onFailure(Call<User> call, Throwable t) {
        Log.e("Apicall", t.getMessage());
    }
});

POST call with form encoding

    String name = "some name";
    String phone = "54686868";
    String id="17479666";

    ApiService.getInstance().updateUser(name, phone, id).enqueue(new Callback<User>() {
        @Override
        public void onResponse(Call<User> call, Response<User> response) {
            //api success
            User user = response.body();
        }

        @Override
        public void onFailure(Call<User> call, Throwable t) {
            Log.e("Apicall", t.getMessage());
        }
    });
}

Synchronous request

You can also call the apis synchronously.

try {            
     List<User> users = ApiService.getInstance().getAllUsers().execute().body();
} catch (IOException e) {
     e.printStackTrace();
}

You cannot run this code in main tread you will get exception like ( java.lang.RuntimeException:Unable to start activity ComponentInfo{  …. } android.os.NetworkOnMainThreadException). So better to use synchronous request in services or asyncTask.

How to create AsyncTask : https://wiki.workassis.com/android-asynctask

How to create Service : https://wiki.workassis.com/android-intentservice-example

Ref : http://square.github.io/retrofit/

Androidmanifest.xml

You need to use NoactionBar theme

----
----
<activity android:name=".SplashActivity"
    android:theme="@style/Theme.AppCompat.Light.NoActionBar">

---
----

Activity class (SplashActivity.java)

public class SplashActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, WindowManager.LayoutParams.FLAG_FULLSCREEN);
        
        super.onCreate(savedInstanceState);


        setContentView(R.layout.activity_splash);
    }
}

There are two step required for implementing Green Dao ORM library in to android project

1. Create generator java module
2. Implement data base interaction in Activity

Step 1. Create generator java module

The generator module contains a single class containing the data model definition. This will automatically generate model class and Dao calss for the database interaction

How to create a generator module?

In android studio got File->New-> New Module select Java Library 

Give library name and class name

After adding the library the folder structure will be like this

add GreenDao dependency in the created module, and sync

compile 'de.greenrobot:greendao-generator:2.1.0'

for Green dao 3.x please use the plugin

compile 'org.greenrobot:greendao-generator:3.1.0'

Add the following code in GeneratorClass.java file. Here we defining a users table scema

import de.greenrobot.daogenerator.DaoGenerator;
import de.greenrobot.daogenerator.Entity;
import de.greenrobot.daogenerator.Schema;

public class GeneratorClass {

    public static void main(String[] args)  throws Exception {

        //place where db folder will be created inside the project folder
        Schema schema = new Schema(1,"samples.bm.com.greendaoe1.db");

        //Entity Users or table Users
        Entity user= schema.addEntity("Users");
        user.addIdProperty();                       //It is the primary key for uniquely identifying a row
        user.addStringProperty("name").notNull();    //Not null is SQL constrain
        user.addStringProperty("email");
        user.addStringProperty("password");
        //user.addDateProperty("date");

        //  ./app/src/main/java/   ----   com/codekrypt/greendao/db is the full path
        new DaoGenerator().generateAll(schema, "./app/src/main/java");
    }
}

for Green dao 3.x:- just change the imports

import org.greenrobot.greendao.generator.DaoGenerator;
import org.greenrobot.greendao.generator.Entity;
import org.greenrobot.greendao.generator.Schema;

Run GeneratorClass.java file

It will Create a db folder inside out main app package

2. Implement data base interaction in Activity

Add Green Dao gradle dependency in our main project and sync

compile 'de.greenrobot:greendao:2.1.0'

for Green dao 3.x:-

compile 'org.greenrobot:greendao:3.1.1'

MainActivity .java

import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.BaseAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

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

import samples.bm.com.greendaoe1.db.DaoMaster;
import samples.bm.com.greendaoe1.db.DaoSession;
import samples.bm.com.greendaoe1.db.Users;
import samples.bm.com.greendaoe1.db.UsersDao;


public class MainActivity extends AppCompatActivity {

    //Dao --> Data Access Object
    private UsersDao userDao; // Sql access object

    private final String DB_NAME = "my-app-db";  //Name of Db file in the Device

    EditText mEtName;
    EditText mEtEmail;
    EditText mEtPassword;

    ArrayAdapter<String> mAdapter;
    ListView mListView;

    List<String> mResult = new ArrayList<>();

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

        //Initialise DAO
        userDao = setupDb();

        //Setting up form elements
        Button btnSave = (Button) findViewById(R.id.btn_Save);

        mEtName = (EditText) findViewById(R.id.et_name);
        mEtEmail = (EditText) findViewById(R.id.et_email);
        mEtPassword = (EditText) findViewById(R.id.et_password);

        mListView = (ListView) findViewById(R.id.lv_result);

        mAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, android.R.id.text1, mResult);
        mListView.setAdapter(mAdapter);

        btnSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String name = mEtName.getText().toString();
                String email = mEtEmail.getText().toString();
                String password = mEtPassword.getText().toString();

                Users user = new Users(null, name, email, password);// Class Object, Id is auto increment

                SaveToSQL(user);

                generateResult();

                mEtName.setText("");
                mEtEmail.setText("");
                mEtPassword.setText("");
            }
        });

        generateResult();
    }

    private void generateResult() {
        List<Users> usersList = getFromSQL();
        int size = usersList.size();

        if (size > 0) {
            mResult.clear();

            for (int i = 0; i < size; i++) {
                Users currentItem = usersList.get(i);
                mResult.add (0,currentItem.getId() + ", " + currentItem.getName() + ", " + currentItem.getEmail() + ", " + currentItem.getPassword());
            }

            ((BaseAdapter) mListView.getAdapter()).notifyDataSetChanged();
        }
    }


    //---------------------------------SQL QUERY Functions-----------------------------------------//
    public List<Users> getFromSQL() {
        List<Users> userses = userDao.queryBuilder().orderDesc(UsersDao.Properties.Id).build().list();
        return userses;
    }

    public void SaveToSQL(Users user) {
        userDao.insert(user);
    }
    //----------------------------***END SQL QUERY***---------------------------------------------//


    //-------------------------------DB Setup Functions---------------------------------------------//

    //Return the Configured LogDao Object
    public UsersDao setupDb() {
        DaoMaster.DevOpenHelper masterHelper = new DaoMaster.DevOpenHelper(this, DB_NAME, null); //create database db file if not exist
        SQLiteDatabase db = masterHelper.getWritableDatabase();  //get the created database db file
        DaoMaster master = new DaoMaster(db);//create masterDao
        DaoSession masterSession = master.newSession(); //Creates Session session
        return masterSession.getUsersDao();
    }
    //-------------------------***END DB setup Functions***---------------------------------------//

}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="samples.bm.com.greendaoe1.MainActivity">


    <EditText
        android:id="@+id/et_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Name" />

    <EditText
        android:id="@+id/et_email"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Email" />

    <EditText
        android:id="@+id/et_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Password" />

    <Button
        android:id="@+id/btn_Save"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Save" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="10dp"

        android:layout_marginTop="20dp"
        android:text="Result"
        android:textStyle="bold" />

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

</LinearLayout>

Out Put

Note:-

While running you app you need to set app from tine toolbar and run

Ref:

http://greenrobot.org/greendao/

Android RecyclerView example using view hodelr in adapter

(For using multiple layout in RecyclerView check this tutorial )

Add ‘com.android.support:recyclerview‘ in Gradle dependencies and sync it

my app/build.gradle file

apply plugin: 'com.android.application'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.1"

    defaultConfig {
        applicationId "samples.bm.com.myapplication"
        minSdkVersion 14
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    testCompile 'junit:junit:4.12'
    compile 'com.android.support:appcompat-v7:24.2.0'

    compile 'com.android.support:recyclerview-v7:24.2.0'
}

MainActivity

package samples.bm.com.myapplication;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.widget.Toast;
import java.util.ArrayList;

public class MainActivity extends AppCompatActivity implements MyMediatorInterface {

    private MyAdapter mAdapter;
    private ArrayList<UserModel> usersList;

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

        usersList = new ArrayList<>();

        usersList.add(new UserModel("Jos", "123546567"));
        usersList.add(new UserModel("Kiran", "456546456"));
        usersList.add(new UserModel("Manu", "5678"));
        usersList.add(new UserModel("Roy", "67443453"));
        usersList.add(new UserModel("Musthu", "456353"));
        usersList.add(new UserModel("Jaffer", "4644"));

        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rv_my_recycler_view);
        recyclerView.setHasFixedSize(true);

        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        mAdapter = new MyAdapter(usersList, this);
        recyclerView.setAdapter(mAdapter);

    }

    @Override
    public void userItemClick(int pos) {
        Toast.makeText(MainActivity.this, "Clicked User : " + usersList.get(pos).name, Toast.LENGTH_SHORT).show();
    }
}

Model

package samples.bm.com.myapplication;

public class UserModel {
    public String name;
    public String phone;

    public UserModel(String name, String phone) {
        this.name = name;
        this.phone = phone;
    }
}

Adapter

package samples.bm.com.myapplication;

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.LinearLayout;
import android.widget.TextView;
import java.lang.ref.WeakReference;
import java.util.ArrayList;


public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    ArrayList<UserModel> mUsersList;
    WeakReference<Context> mContextWeakReference;

    public MyAdapter(ArrayList<UserModel> usersList, Context context) {
        mUsersList = usersList;
        this.mContextWeakReference = new WeakReference<Context>(context);
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        Context context = mContextWeakReference.get();

        if (context != null) {

            View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_user_item, parent, false);

            return new MyViewHolder(itemView, context);
        }

        return null;
    }

    @Override
    public void onBindViewHolder(final MyViewHolder holder, int position) {

        Context context = mContextWeakReference.get();

        if (context == null) {
            return;
        }

        UserModel currentUser = mUsersList.get(position);

        holder.TvName.setText(currentUser.name);
        holder.TvPhone.setText(currentUser.phone);

    }

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

    //holder
    public static class MyViewHolder extends RecyclerView.ViewHolder {

        public TextView TvName, TvPhone;
        public LinearLayout ll;

        public MyViewHolder(View itemView, final Context context) {

            super(itemView);
            TvName = (TextView) itemView.findViewById(R.id.tv_name);
            TvPhone = (TextView) itemView.findViewById(R.id.tv_phone);
            ll = (LinearLayout) itemView.findViewById(R.id.ll_layout);

            ll.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View view) {
                    ((MainActivity) context).userItemClick(getAdapterPosition());
                }
            });
        }
    }
}

Interface:

package samples.bm.com.myapplication;

public interface MyMediatorInterface {
    void userItemClick(int pos);
}

Layouts

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="samples.bm.com.myapplication.MainActivity"
    android:orientation="vertical">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!" />

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

</LinearLayout>

Recycler View row

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:id="@+id/ll_layout"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:padding="20px">

    <TextView
        android:id="@+id/tv_name"
        android:layout_width="0dp"
        android:layout_weight="1"
        android:layout_height="wrap_content" />

    <TextView
        android:id="@+id/tv_phone"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="right" />
</LinearLayout>

Out Put

If you want to add data to RecyclerView  add data into the Array List (eg:- usersList.add(new UserModel(“new name”, “345”)); and you can call the adapter function notifyItemInserted() or notifyDatasetChanged().

mAdapter.notifyItemInserted(position);

mAdapter.notifyDataSetChanged(); //this function you can call with any activity (inset,update,delete) but it is expensive

While editing edit the value in array list and call notifyItemChanged(position), while deleting delete the position from array list and call notifyItemRemoved(position)

String

String objects are immutable ( once created can not be changed ) and it will stored in the  Constant String Pool , so if you chose to do a lot of manipulations with String objects, you will end up with a lot of abandoned String objects in the String pool. To avoiding this memory loss we can use StringBuilder or StringBuffer and can be modified over and over again without causing memory loss

StringBuilder example

StringBuffers are thread-safe, they have synchronized methods to control access so that only one thread can access a StringBuffer object’s synchronized code at a time. Thus, StringBuffer objects are generally safe to use in a multi-threaded environment where multiple threads may be trying to access the same StringBuffer object at the same time.

        String from = "From : ";
        String to = " To : ";

        StringBuilder builder = new StringBuilder();
        builder.append(from);
        builder.append("Manager");
        builder.append(to);
        builder.append("Developer");

        Log.i("Result : ", builder.toString());

StringBuffer example

StringBuilder’s access is not synchronized so that it is not thread-safe. The performance of StringBuilder can be better than StringBuffer. Thus, if you are working in a single-threaded environment, using StringBuilder instead of StringBuffer may result in increased performance.

        String from = "From : ";
        String to = " To : ";

        String str = new StringBuffer()
                .append(from)
                .append("Manager")
                .append(to)
                .append("Developer")
                .toString();


        Log.i("Result : ",str);

ref:
https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuilder.html

https://docs.oracle.com/javase/tutorial/java/data/buffers.html

https://docs.oracle.com/javase/7/docs/api/java/lang/StringBuffer.html