Ejemplo base de datos Realm. Curso de desarrollo de aplicaciones Android.

activity_adicionar.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"
    tools:context="tech.alvarez.mislibros.AdicionarActivity">

    <LinearLayout
        android:padding="16dp"
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <EditText
            android:id="@+id/tituloEditText"
            android:hint="@string/titulo"
            android:layout_width="match_parent"
            android:layout_height="48dp" />

        <EditText
            android:id="@+id/autorEditText"
            android:hint="@string/autor"
            android:layout_width="match_parent"
            android:layout_height="48dp" />

        <RatingBar
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/ratingBar"
            android:layout_gravity="center_horizontal" />


    </LinearLayout>


    <android.support.design.widget.FloatingActionButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="16dp"
        android:onClick="guardarLibro"
        android:src="@drawable/ic_save_white_24dp" />


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

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 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"
    tools:context="tech.alvarez.mislibros.MainActivity">

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

    <android.support.design.widget.FloatingActionButton
        android:onClick="adicionar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="16dp"
        android:src="@drawable/ic_add_white_24dp" />

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

AdicionarActivity.java

package tech.alvarez.mislibros;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.RatingBar;

import io.realm.Realm;
import tech.alvarez.mislibros.models.Libro;

public class AdicionarActivity extends AppCompatActivity {

    public Realm realm;

    private EditText tituloEditText;
    private EditText autorEditText;
    private RatingBar ratingBar;

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

        realm = Realm.getDefaultInstance();

        tituloEditText = (EditText) findViewById(R.id.tituloEditText);
        autorEditText = (EditText) findViewById(R.id.autorEditText);
        ratingBar = (RatingBar) findViewById(R.id.ratingBar);
    }

    public void guardarLibro(View view) {

        String titulo = tituloEditText.getText().toString();
        String autor = autorEditText.getText().toString();
        float puntaje = ratingBar.getRating();

        realm.beginTransaction();
        Libro li = realm.createObject(Libro.class);
        li.setTitulo(titulo);
        li.setAutor(autor);
        li.setPuntaje(puntaje);
        realm.commitTransaction();

        finish();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        realm.close();
    }
}

buildmodulo.gradle

apply plugin: 'com.android.application'
apply plugin: 'realm-android'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.0"

    defaultConfig {
        applicationId "tech.alvarez.mislibros"
        minSdkVersion 15
        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-v7:24.0.0'
    compile 'com.android.support:design:24.0.0'
    compile 'com.android.support:cardview-v7:24.0.0'
    compile 'com.android.support:recyclerview-v7:24.0.0'



}

buildproject.gradle

// Top-level build file where you can add configuration options common to all sub-projects/modules.

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.1.2'

        classpath "io.realm:realm-gradle-plugin:1.1.0"
        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

colors.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <color name="colorPrimary">#3F51B5</color>
    <color name="colorPrimaryDark">#303F9F</color>
    <color name="colorAccent">#FF4081</color>

    <color name="colorPrimaryText">#DE000000</color>
    <color name="colorSecondaryText">#8A000000</color>
    <color name="colorDisabledText">#61000000</color>

    <color name="colorPrimaryDarkText">#FFFFFF</color>
    <color name="colorSecondaryDarkText">#B3FFFFFF</color>
    <color name="colorDisabledDarkText">#80FFFFFF</color>
</resources>

item_libro.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="72dp"
    android:layout_marginBottom="0dp"
    android:layout_marginLeft="8dp"
    android:layout_marginRight="8dp"
    android:layout_marginTop="8dp"
    android:orientation="horizontal"
    card_view:cardCornerRadius="4dp">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center"
        android:gravity="center_vertical"
        android:orientation="vertical"
        android:paddingLeft="16dp"
        android:paddingRight="16dp">

        <TextView
            android:id="@+id/tituloTextView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/app_name"
            android:textColor="@color/colorPrimaryText"
            android:textSize="16sp" />

        <TextView
            android:id="@+id/autorTextView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="@string/app_name"
            android:textColor="@color/colorSecondaryText"
            android:textSize="14sp" />

        <TextView
            android:id="@+id/puntajeTextView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center_vertical"
            android:text="@string/app_name"
            android:textColor="@color/colorAccent"
            android:textSize="12sp" />
    </LinearLayout>

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

ItemClickOyente.java

package tech.alvarez.mislibros.adapters;

import tech.alvarez.mislibros.models.Libro;

/**
 * Created by Daniel Alvarez on 14/7/16.
 * Copyright © 2016 Alvarez.tech. All rights reserved.
 */
public interface ItemClickOyente {

    void onItemClick(Libro libro);

}

Libro.java

package tech.alvarez.mislibros.models;

import io.realm.RealmObject;

/**
 * Created by Daniel Alvarez on 13/7/16.
 * Copyright © 2016 Alvarez.tech. All rights reserved.
 */
public class Libro extends RealmObject{

    private String titulo;
    private String autor;
    private float puntaje;

    public String getTitulo() {
        return titulo;
    }

    public void setTitulo(String titulo) {
        this.titulo = titulo;
    }

    public String getAutor() {
        return autor;
    }

    public void setAutor(String autor) {
        this.autor = autor;
    }

    public float getPuntaje() {
        return puntaje;
    }

    public void setPuntaje(float puntaje) {
        this.puntaje = puntaje;
    }
}

LibrosAdapter.java

package tech.alvarez.mislibros.adapters;

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

import io.realm.RealmResults;
import tech.alvarez.mislibros.R;
import tech.alvarez.mislibros.models.Libro;

/**
 * Created by Daniel Alvarez on 13/7/16.
 * Copyright © 2016 Alvarez.tech. All rights reserved.
 */
public class LibrosAdapter extends RecyclerView.Adapter<LibrosAdapter.ViewHolder> {

    private RealmResults<Libro> dataset;
    private ItemClickOyente itemClickOyente;

    public LibrosAdapter(RealmResults<Libro> dataset, ItemClickOyente itemClickOyente) {
        this.dataset = dataset;
        this.itemClickOyente = itemClickOyente;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_libro, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        Libro libro = dataset.get(position);
        holder.tituloTextView.setText(libro.getTitulo());
        holder.autorTextView.setText(libro.getAutor());
        holder.puntajeTextView.setText(libro.getPuntaje() + "");

        holder.setItemClick(libro, itemClickOyente);
    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder {

        private TextView tituloTextView;
        private TextView autorTextView;
        private TextView puntajeTextView;

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

            tituloTextView = (TextView) itemView.findViewById(R.id.tituloTextView);
            autorTextView = (TextView) itemView.findViewById(R.id.autorTextView);
            puntajeTextView = (TextView) itemView.findViewById(R.id.puntajeTextView);
        }

        public void setItemClick(final Libro libro, final ItemClickOyente itemClickOyente) {
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    itemClickOyente.onItemClick(libro);
                }
            });
        }
    }
}

MainActivity.java

package tech.alvarez.mislibros;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.Toast;

import io.realm.Realm;
import io.realm.RealmQuery;
import io.realm.RealmResults;
import io.realm.Sort;
import tech.alvarez.mislibros.adapters.ItemClickOyente;
import tech.alvarez.mislibros.adapters.LibrosAdapter;
import tech.alvarez.mislibros.models.Libro;

public class MainActivity extends AppCompatActivity implements ItemClickOyente{

    public Realm realm;

    private RecyclerView librosRecyclerView;

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

        realm = Realm.getDefaultInstance();

        librosRecyclerView = (RecyclerView) findViewById(R.id.librosRecyclerView);
        librosRecyclerView.setHasFixedSize(true);
        librosRecyclerView.setLayoutManager(new LinearLayoutManager(this));
    }

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

        actualizarDatos();
    }

    public void adicionar(View view) {

        Intent intent = new Intent(this, AdicionarActivity.class);
        startActivity(intent);

    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        realm.close();
    }


    public void actualizarDatos() {
        RealmQuery<Libro> query = realm.where(Libro.class);
        RealmResults<Libro> results = query.findAll();
        results = results.sort("puntaje", Sort.DESCENDING);

        librosRecyclerView.setAdapter(new LibrosAdapter(results, this));
    }

    @Override
    public void onItemClick(Libro libro) {
//        Toast.makeText(getApplicationContext(), libro.getTitulo(), Toast.LENGTH_SHORT).show();

//        realm.beginTransaction();
//        libro.setAutor("Maria Loza");
//        realm.commitTransaction();

        realm.beginTransaction();
        libro.deleteFromRealm();
        realm.commitTransaction();

        actualizarDatos();
    }
}

MisLibrosApp.java

package tech.alvarez.mislibros;

import android.app.Application;

import io.realm.Realm;
import io.realm.RealmConfiguration;

/**
 * Created by Daniel Alvarez on 13/7/16.
 * Copyright © 2016 Alvarez.tech. All rights reserved.
 */
public class MisLibrosApp extends Application {

    @Override
    public void onCreate() {
        super.onCreate();

        RealmConfiguration realmConfiguration = new RealmConfiguration.Builder(this).build();
        Realm.setDefaultConfiguration(realmConfiguration);

    }
}