adding firebase lecture CRUD demo

.gitignore

+*.iml
+.gradle
+/local.properties
+/.idea/libraries
+/.idea/modules.xml
+/.idea/workspace.xml
+.DS_Store
+/build
+/captures
+.externalNativeBuild

.idea/codeStyles/Project.xml

+<component name="ProjectCodeStyleConfiguration">
+  <code_scheme name="Project" version="173">
+    <Objective-C-extensions>
+      <file>
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Import" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Macro" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Typedef" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Enum" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Constant" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Global" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Struct" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="FunctionPredecl" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Function" />
+      </file>
+      <class>
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Property" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="Synthesize" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="InitMethod" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="StaticMethod" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="InstanceMethod" />
+        <option name="com.jetbrains.cidr.lang.util.OCDeclarationKind" value="DeallocMethod" />
+      </class>
+      <extensions>
+        <pair source="cpp" header="h" fileNamingConvention="NONE" />
+        <pair source="c" header="h" fileNamingConvention="NONE" />
+      </extensions>
+    </Objective-C-extensions>
+  </code_scheme>
+</component>
\ No newline at end of file

.idea/gradle.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="GradleSettings">
+    <option name="linkedExternalProjectsSettings">
+      <GradleProjectSettings>
+        <option name="distributionType" value="DEFAULT_WRAPPED" />
+        <option name="externalProjectPath" value="$PROJECT_DIR$" />
+        <option name="modules">
+          <set>
+            <option value="$PROJECT_DIR$" />
+            <option value="$PROJECT_DIR$/app" />
+          </set>
+        </option>
+        <option name="resolveModulePerSourceSet" value="false" />
+      </GradleProjectSettings>
+    </option>
+  </component>
+</project>
\ No newline at end of file

.idea/misc.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="NullableNotNullManager">
+    <option name="myDefaultNullable" value="android.support.annotation.Nullable" />
+    <option name="myDefaultNotNull" value="android.support.annotation.NonNull" />
+    <option name="myNullables">
+      <value>
+        <list size="5">
+          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.Nullable" />
+          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nullable" />
+          <item index="2" class="java.lang.String" itemvalue="javax.annotation.CheckForNull" />
+          <item index="3" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.Nullable" />
+          <item index="4" class="java.lang.String" itemvalue="android.support.annotation.Nullable" />
+        </list>
+      </value>
+    </option>
+    <option name="myNotNulls">
+      <value>
+        <list size="4">
+          <item index="0" class="java.lang.String" itemvalue="org.jetbrains.annotations.NotNull" />
+          <item index="1" class="java.lang.String" itemvalue="javax.annotation.Nonnull" />
+          <item index="2" class="java.lang.String" itemvalue="edu.umd.cs.findbugs.annotations.NonNull" />
+          <item index="3" class="java.lang.String" itemvalue="android.support.annotation.NonNull" />
+        </list>
+      </value>
+    </option>
+  </component>
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_7" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+    <output url="file://$PROJECT_DIR$/build/classes" />
+  </component>
+  <component name="ProjectType">
+    <option name="id" value="Android" />
+  </component>
+</project>
\ No newline at end of file

.idea/runConfigurations.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="RunConfigurationProducerService">
+    <option name="ignoredProducers">
+      <set>
+        <option value="org.jetbrains.plugins.gradle.execution.test.runner.AllInPackageGradleConfigurationProducer" />
+        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestClassGradleConfigurationProducer" />
+        <option value="org.jetbrains.plugins.gradle.execution.test.runner.TestMethodGradleConfigurationProducer" />
+      </set>
+    </option>
+  </component>
+</project>
\ No newline at end of file

.idea/vcs.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>
\ No newline at end of file

app/.gitignore

+/build

app/build.gradle

+apply plugin: 'com.android.application'
+
+android {
+    compileSdkVersion 28
+    defaultConfig {
+        applicationId "com.example.tesla.myhomelibrary"
+        minSdkVersion 26
+        targetSdkVersion 28
+        versionCode 1
+        versionName "1.0"
+        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+    }
+    buildTypes {
+        release {
+            minifyEnabled false
+            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
+        }
+    }
+}
+
+dependencies {
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation 'com.android.support:appcompat-v7:28.0.0'
+    implementation 'com.android.support.constraint:constraint-layout:1.1.3'
+    implementation 'com.google.firebase:firebase-core:16.0.4'
+    implementation 'com.google.firebase:firebase-database:16.0.3'
+    testImplementation 'junit:junit:4.12'
+    testImplementation 'org.mockito:mockito-core:1.10.19'
+    androidTestImplementation 'com.android.support.test:runner:1.0.2'
+    implementation 'com.android.support:support-annotations:28.0.0'
+    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
+    androidTestImplementation 'com.android.support.test:rules:1.0.2'
+}
+
+apply plugin: 'com.google.gms.google-services'
\ No newline at end of file

app/google-services.json

+{
+  "project_info": {
+    "project_number": "29102789333",
+    "firebase_url": "https://myhomelibrary-838ac.firebaseio.com",
+    "project_id": "myhomelibrary-838ac",
+    "storage_bucket": "myhomelibrary-838ac.appspot.com"
+  },
+  "client": [
+    {
+      "client_info": {
+        "mobilesdk_app_id": "1:29102789333:android:7f079efdba385b39",
+        "android_client_info": {
+          "package_name": "com.example.tesla.myhomelibrary"
+        }
+      },
+      "oauth_client": [
+        {
+          "client_id": "29102789333-b0jc7do4lghpm5oo3panm8rgcqrco9at.apps.googleusercontent.com",
+          "client_type": 3
+        }
+      ],
+      "api_key": [
+        {
+          "current_key": "AIzaSyCYVtTDVxur-80vXj37SRHPAvhQeSX8L6U"
+        }
+      ],
+      "services": {
+        "analytics_service": {
+          "status": 1
+        },
+        "appinvite_service": {
+          "status": 1,
+          "other_platform_oauth_client": []
+        },
+        "ads_service": {
+          "status": 2
+        }
+      }
+    }
+  ],
+  "configuration_version": "1"
+}
\ No newline at end of file

app/proguard-rules.pro

+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# proguardFiles setting in build.gradle.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+#-renamesourcefileattribute SourceFile

app/src/androidTest/java/com/example/tesla/myhomelibrary/MainActivityTest.java

+package com.example.tesla.myhomelibrary;
+
+
+import android.support.test.espresso.ViewInteraction;
+import android.support.test.filters.LargeTest;
+import android.support.test.rule.ActivityTestRule;
+import android.support.test.runner.AndroidJUnit4;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.ViewParent;
+
+import org.hamcrest.Description;
+import org.hamcrest.Matcher;
+import org.hamcrest.TypeSafeMatcher;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import static android.support.test.espresso.Espresso.onView;
+import static android.support.test.espresso.assertion.ViewAssertions.matches;
+import static android.support.test.espresso.matcher.ViewMatchers.isDisplayed;
+import static android.support.test.espresso.matcher.ViewMatchers.withId;
+import static android.support.test.espresso.matcher.ViewMatchers.withText;
+import static org.hamcrest.Matchers.allOf;
+
+@LargeTest
+@RunWith(AndroidJUnit4.class)
+public class MainActivityTest {
+
+    @Rule
+   public ActivityTestRule<MainActivity> mActivityTestRule = new ActivityTestRule<>(MainActivity.class);
+
+    @Test
+    public void mainActivityTest() {
+        // Added a sleep statement to match the app's execution delay.
+        // The recommended way to handle such scenarios is to use Espresso idling resources:
+        // https://google.github.io/android-testing-support-library/docs/espresso/idling-resource/index.html
+        try {
+            Thread.sleep(30000);
+        } catch (InterruptedException e) {
+            e.printStackTrace();
+        }
+
+
+        ViewInteraction textView = onView(
+                allOf(withId(R.id.textView), withText("Authors"),
+                        childAtPosition(
+                                allOf(withId(R.id.activity_main),
+                                        childAtPosition(
+                                                withId(android.R.id.content),
+                                                0)),
+                                3),
+                        isDisplayed()));
+        textView.check(matches(withText("Authors")));
+
+        ViewInteraction button = onView(
+                allOf(withId(R.id.buttonAddAuthor),
+                        childAtPosition(
+                                allOf(withId(R.id.activity_main),
+                                        childAtPosition(
+                                                withId(android.R.id.content),
+                                                0)),
+                                2),
+                        isDisplayed()));
+        button.check(matches(isDisplayed()));
+
+        ViewInteraction textView2 = onView(
+                allOf(withId(R.id.textViewName), withText("Ernesto Hemingway"),
+                        childAtPosition(
+                                childAtPosition(
+                                        withId(R.id.listViewAuthors),
+                                        0),
+                                0),
+                        isDisplayed()));
+        textView2.check(matches(withText("Ernesto Hemingway")));
+
+    }
+
+    private static Matcher<View> childAtPosition(
+            final Matcher<View> parentMatcher, final int position) {
+
+        return new TypeSafeMatcher<View>() {
+            @Override
+            public void describeTo(Description description) {
+                description.appendText("Child at position " + position + " in parent ");
+                parentMatcher.describeTo(description);
+            }
+
+            @Override
+            public boolean matchesSafely(View view) {
+                ViewParent parent = view.getParent();
+                return parent instanceof ViewGroup && parentMatcher.matches(parent)
+                        && view.equals(((ViewGroup) parent).getChildAt(position));
+            }
+        };
+    }
+}

app/src/main/AndroidManifest.xml

+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    package="com.example.tesla.myhomelibrary">
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/AppTheme">
+        <activity android:name=".MainActivity">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+        <activity android:name=".AuthorActivity"></activity>
+    </application>
+
+</manifest>
\ No newline at end of file

app/src/main/java/com/example/tesla/myhomelibrary/Author.java

+package com.example.tesla.myhomelibrary;
+
+import com.google.firebase.database.IgnoreExtraProperties;
+
+@IgnoreExtraProperties
+public class Author {
+    private String authorId;
+    private String authorName;
+    private String authorCountry;
+
+    public Author(){
+        //this constructor is required
+    }
+
+    public Author(String authorId, String authorName, String authorCountry) {
+        this.authorId = authorId;
+        this.authorName = authorName;
+        this.authorCountry = authorCountry;
+    }
+
+    public String getAuthorId() {
+        return authorId;
+    }
+
+    public String getAuthorName() { return authorName; }
+
+    public String getAuthorCountry() {
+        return authorCountry;
+    }
+}
\ No newline at end of file

app/src/main/java/com/example/tesla/myhomelibrary/AuthorActivity.java

+package com.example.tesla.myhomelibrary;
+
+import android.content.Intent;
+import android.support.v7.app.AppCompatActivity;
+import android.os.Bundle;
+import android.text.TextUtils;
+import android.view.View;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.ListView;
+import android.widget.SeekBar;
+import android.widget.TextView;
+import android.widget.Toast;
+
+import com.google.firebase.database.DataSnapshot;
+import com.google.firebase.database.DatabaseError;
+import com.google.firebase.database.DatabaseReference;
+import com.google.firebase.database.FirebaseDatabase;
+import com.google.firebase.database.ValueEventListener;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class AuthorActivity extends AppCompatActivity {
+    Button buttonAddTitle;
+    EditText editTextTitleName;
+    SeekBar seekBarRating;
+    TextView textViewRating, textViewAuthor;
+    ListView listViewTitles;
+
+    DatabaseReference databaseTitles;
+
+    List<Title> titles;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_author);
+
+        Intent intent = getIntent();
+
+        /*
+         * this line is important
+         * this time we are not getting the reference of a direct node
+         * but inside the node track we are creating a new child with the author id
+         * and inside that node we will store all the titles with unique ids
+         * */
+        databaseTitles = FirebaseDatabase.getInstance().getReference("titles").child(intent.getStringExtra(MainActivity.AUTHOR_ID));
+
+        buttonAddTitle = (Button) findViewById(R.id.buttonAddTitle);
+        editTextTitleName = (EditText) findViewById(R.id.editTextName);
+        seekBarRating = (SeekBar) findViewById(R.id.seekBarRating);
+        textViewRating = (TextView) findViewById(R.id.textViewRating);
+        textViewAuthor = (TextView) findViewById(R.id.textViewAuthor);
+        listViewTitles = (ListView) findViewById(R.id.listViewTitles);
+
+        titles = new ArrayList<Title>();
+
+        textViewAuthor.setText(intent.getStringExtra(MainActivity.AUTHOR_NAME));
+
+        seekBarRating.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
+            @Override
+            public void onProgressChanged(SeekBar seekBar, int i, boolean b) {
+                textViewRating.setText(String.valueOf(i));
+            }
+
+            @Override
+            public void onStartTrackingTouch(SeekBar seekBar) {
+
+            }
+
+            @Override
+            public void onStopTrackingTouch(SeekBar seekBar) {
+
+            }
+        });
+
+        buttonAddTitle.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                saveTitle();
+            }
+        });
+    }
+
+    @Override
+    protected void onStart() {
+        super.onStart();
+
+        databaseTitles.addValueEventListener(new ValueEventListener() {
+            @Override
+            public void onDataChange(DataSnapshot dataSnapshot) {
+                titles.clear();
+                for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
+                    Title title = postSnapshot.getValue(Title.class);
+                    titles.add(title);
+                }
+                TitleList titleListAdapter = new TitleList(AuthorActivity.this, titles);
+                listViewTitles.setAdapter(titleListAdapter);
+            }
+
+            @Override
+            public void onCancelled(DatabaseError databaseError) {
+
+            }
+        });
+    }
+
+    private void saveTitle() {
+        String titleName = editTextTitleName.getText().toString().trim();
+        int rating = seekBarRating.getProgress();
+        if (!TextUtils.isEmpty(titleName)) {
+            String id  = databaseTitles.push().getKey();
+            Title title = new Title(id, titleName, rating);
+            databaseTitles.child(id).setValue(title);
+            Toast.makeText(this, "Title saved", Toast.LENGTH_LONG).show();
+            editTextTitleName.setText("");
+        } else {
+            Toast.makeText(this, "Please enter title name", Toast.LENGTH_LONG).show();
+        }
+    }
+}

app/src/main/java/com/example/tesla/myhomelibrary/AuthorList.java

+package com.example.tesla.myhomelibrary;
+
+import android.app.Activity;
+import android.support.annotation.NonNull;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ArrayAdapter;
+import android.widget.TextView;
+
+import java.util.List;
+
+
+public class AuthorList extends ArrayAdapter<Author> {
+    private Activity context;
+    List<Author> authors;
+
+    public AuthorList(Activity context, List<Author> authors) {
+        super(context, R.layout.layout_author_list, authors);
+        this.context = context;
+        this.authors = authors;
+    }
+
+
+    @Override
+    public View getView(int position, View convertView, ViewGroup parent) {
+        LayoutInflater inflater = context.getLayoutInflater();
+        View listViewItem = inflater.inflate(R.layout.layout_author_list, null, true);
+
+        TextView textViewName = (TextView) listViewItem.findViewById(R.id.textViewName);
+        TextView textViewCountry = (TextView) listViewItem.findViewById(R.id.textViewCountry);
+
+        Author author = authors.get(position);
+        textViewName.setText(author.getAuthorName());
+        textViewCountry.setText(author.getAuthorCountry());
+
+        return listViewItem;
+    }
+}
\ No newline at end of file

app/src/main/java/com/example/tesla/myhomelibrary/MainActivity.java

+package com.example.tesla.myhomelibrary;
+
+import android.content.Intent;
+import android.support.v7.app.AlertDialog;
+import android.support.v7.app.AppCompatActivity;
+import android.os.Bundle;
+import android.text.TextUtils;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.widget.AdapterView;
+import android.widget.ArrayAdapter;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.ListView;
+import android.widget.Spinner;
+import android.widget.Toast;
+
+import com.google.firebase.database.DataSnapshot;
+import com.google.firebase.database.DatabaseError;
+import com.google.firebase.database.DatabaseReference;
+import com.google.firebase.database.FirebaseDatabase;
+import com.google.firebase.database.ValueEventListener;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class MainActivity extends AppCompatActivity {
+    public static final String AUTHOR_NAME = "com.example.tesla.myhomelibrary.authorname";
+    public static final String AUTHOR_ID = "com.example.tesla.myhomelibrary.authorid";
+
+    EditText editTextName;
+    Spinner spinnerCountry;
+    Button buttonAddAuthor;
+    ListView listViewAuthors;
+
+    //a list to store all the artist from firebase database
+    List<Author> authors;
+
+    //our database reference object
+    DatabaseReference databaseAuthors;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+
+        //getting the reference of artists node
+        databaseAuthors = FirebaseDatabase.getInstance().getReference("authors");
+
+        //getting views
+        editTextName = (EditText) findViewById(R.id.editTextName);
+        spinnerCountry = (Spinner) findViewById(R.id.spinnerCountry);
+        listViewAuthors = (ListView) findViewById(R.id.listViewAuthors);
+
+        buttonAddAuthor = (Button) findViewById(R.id.buttonAddAuthor);
+
+        //list to store authors
+        authors = new ArrayList<>();
+
+
+        //adding an onclicklistener to button
+        buttonAddAuthor.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                //calling the method addArtist()
+                //the method is defined below
+                //this method is actually performing the write operation
+                addAuthor();
+            }
+        });
+
+        //attaching listener to listview
+        listViewAuthors.setOnItemClickListener(new AdapterView.OnItemClickListener() {
+            @Override
+            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
+                //getting the selected artist
+                Author author = authors.get(i);
+
+                //creating an intent
+                Intent intent = new Intent(getApplicationContext(), AuthorActivity.class);
+
+                //putting artist name and id to intent
+                intent.putExtra(AUTHOR_ID, author.getAuthorId());
+                intent.putExtra(AUTHOR_NAME, author.getAuthorName());
+
+                //starting the activity with intent
+                startActivity(intent);
+            }
+        });
+
+        listViewAuthors.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
+            @Override
+            public boolean onItemLongClick(AdapterView<?> adapterView, View view, int i, long l) {
+                Author author = authors.get(i);
+                showUpdateDeleteDialog(author.getAuthorId(), author.getAuthorName());
+                return true;
+            }
+        });
+    }
+
+    private void showUpdateDeleteDialog(final String authorId, String authorName) {
+
+        AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
+        LayoutInflater inflater = getLayoutInflater();
+        final View dialogView = inflater.inflate(R.layout.update_dialog, null);
+        dialogBuilder.setView(dialogView);
+
+        final EditText editTextName = (EditText) dialogView.findViewById(R.id.editTextName);
+        final Spinner spinnerCountry = (Spinner) dialogView.findViewById(R.id.spinnerCountry);
+        final Button buttonUpdate = (Button) dialogView.findViewById(R.id.buttonUpdateAuthor);
+        final Button buttonDelete = (Button) dialogView.findViewById(R.id.buttonDeleteAuthor);
+
+        dialogBuilder.setTitle(authorName);
+        final AlertDialog b = dialogBuilder.create();
+        b.show();
+
+
+        buttonUpdate.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+                String name = editTextName.getText().toString().trim();
+                String country = spinnerCountry.getSelectedItem().toString();
+                if (!TextUtils.isEmpty(name)) {
+                    updateAuthor(authorId, name, country);
+                    b.dismiss();
+                }
+            }
+        });
+
+
+        buttonDelete.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View view) {
+
+                deleteAuthor(authorId);
+                b.dismiss();
+            }
+        });
+    }
+
+
+    private boolean updateAuthor(String id, String name, String country) {
+        //getting the specified author reference
+        DatabaseReference dR = FirebaseDatabase.getInstance().getReference("authors").child(id);
+
+        //updating author
+        Author author = new Author(id, name, country);
+        dR.setValue(author);
+        Toast.makeText(getApplicationContext(), "Author Updated", Toast.LENGTH_LONG).show();
+        return true;
+    }
+
+    private boolean deleteAuthor(String id) {
+        //getting the specified author reference
+        DatabaseReference dR = FirebaseDatabase.getInstance().getReference("authors").child(id);
+
+        //removing author
+        dR.removeValue();
+
+        //getting the titles reference for the specified author
+        DatabaseReference drTitles = FirebaseDatabase.getInstance().getReference("titles").child(id);
+
+        //removing all titles
+        drTitles.removeValue();
+        Toast.makeText(getApplicationContext(), "Author Deleted", Toast.LENGTH_LONG).show();
+
+        return true;
+    }
+
+    @Override
+    protected void onStart() {
+        super.onStart();
+        //attaching value event listener
+        databaseAuthors.addValueEventListener(new ValueEventListener() {
+            @Override
+            public void onDataChange(DataSnapshot dataSnapshot) {
+
+                //clearing the previous artist list
+                authors.clear();
+
+                //iterating through all the nodes
+                for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
+                    //getting artist
+                    Author author = postSnapshot.getValue(Author.class);
+                    //adding author to the list
+                    authors.add(author);
+                }
+
+                //creating adapter
+                AuthorList authorAdapter = new AuthorList(MainActivity.this, authors);
+                //attaching adapter to the listview
+                listViewAuthors.setAdapter(authorAdapter);
+            }
+
+            @Override
+            public void onCancelled(DatabaseError databaseError) {
+
+            }
+        });
+    }
+
+
+    /*
+     * This method is saving a new author to the
+     * Firebase Realtime Database
+     * */
+    private void addAuthor() {
+        //getting the values to save
+        String name = editTextName.getText().toString().trim();
+        String country = spinnerCountry.getSelectedItem().toString();
+
+        //checking if the value is provided
+        if (!TextUtils.isEmpty(name)) {
+
+            //getting a unique id using push().getKey() method
+            //it will create a unique id and we will use it as the Primary Key for our Author
+            String id = databaseAuthors.push().getKey();
+
+            //creating an Author Object
+            Author author = new Author(id, name, country);
+
+            //Saving the Author
+            databaseAuthors.child(id).setValue(author);
+
+            //setting edittext to blank again
+            editTextName.setText("");
+
+            //displaying a success toast
+            Toast.makeText(this, "Author added", Toast.LENGTH_LONG).show();
+        } else {
+            //if the value is not given displaying a toast
+            Toast.makeText(this, "Please enter a name", Toast.LENGTH_LONG).show();
+        }
+    }
+}
+

app/src/main/java/com/example/tesla/myhomelibrary/Title.java

+package com.example.tesla.myhomelibrary;
+
+import com.google.firebase.database.IgnoreExtraProperties;
+
+@IgnoreExtraProperties
+public class Title {
+    private String id;
+    private String titleName;
+    private int rating;
+
+    public Title() {
+
+    }
+
+    public Title(String id, String titleName, int rating) {
+        this.titleName = titleName;
+        this.rating = rating;
+        this.id = id;
+    }
+
+    public String getTitleName() {
+        return titleName;
+    }
+
+    public int getRating() {
+        return rating;
+    }
+}

app/src/main/java/com/example/tesla/myhomelibrary/TitleList.java

+package com.example.tesla.myhomelibrary;
+
+import android.app.Activity;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.widget.ArrayAdapter;
+import android.widget.TextView;
+
+import java.util.List;
+
+public class TitleList extends ArrayAdapter<Title> {
+    private Activity context;
+    List<Title> titles;
+
+    public TitleList(Activity context, List<Title> titles) {
+        super(context, R.layout.layout_author_list, titles);
+        this.context = context;
+        this.titles = titles;
+    }
+
+
+    @Override
+    public View getView(int position, View convertView, ViewGroup parent) {
+        LayoutInflater inflater = context.getLayoutInflater();
+        View listViewItem = inflater.inflate(R.layout.layout_author_list, null, true);
+
+        TextView textViewName = (TextView) listViewItem.findViewById(R.id.textViewName);
+        TextView textViewRating = (TextView) listViewItem.findViewById(R.id.textViewCountry);
+
+        Title title = titles.get(position);
+        textViewName.setText(title.getTitleName());
+        textViewRating.setText(String.valueOf(title.getRating()));
+
+        return listViewItem;
+    }
+}

app/src/main/res/drawable-v24/ic_launcher_foreground.xml

+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:aapt="http://schemas.android.com/aapt"
+    android:width="108dp"
+    android:height="108dp"
+    android:viewportHeight="108"
+    android:viewportWidth="108">
+    <path
+        android:fillType="evenOdd"
+        android:pathData="M32,64C32,64 38.39,52.99 44.13,50.95C51.37,48.37 70.14,49.57 70.14,49.57L108.26,87.69L108,109.01L75.97,107.97L32,64Z"
+        android:strokeColor="#00000000"
+        android:strokeWidth="1">
+        <aapt:attr name="android:fillColor">
+            <gradient
+                android:endX="78.5885"
+                android:endY="90.9159"
+                android:startX="48.7653"
+                android:startY="61.0927"
+                android:type="linear">
+                <item
+                    android:color="#44000000"
+                    android:offset="0.0" />
+                <item
+                    android:color="#00000000"
+                    android:offset="1.0" />
+            </gradient>
+        </aapt:attr>
+    </path>
+    <path
+        android:fillColor="#FFFFFF"
+        android:fillType="nonZero"
+        android:pathData="M66.94,46.02L66.94,46.02C72.44,50.07 76,56.61 76,64L32,64C32,56.61 35.56,50.11 40.98,46.06L36.18,41.19C35.45,40.45 35.45,39.3 36.18,38.56C36.91,37.81 38.05,37.81 38.78,38.56L44.25,44.05C47.18,42.57 50.48,41.71 54,41.71C57.48,41.71 60.78,42.57 63.68,44.05L69.11,38.56C69.84,37.81 70.98,37.81 71.71,38.56C72.44,39.3 72.44,40.45 71.71,41.19L66.94,46.02ZM62.94,56.92C64.08,56.92 65,56.01 65,54.88C65,53.76 64.08,52.85 62.94,52.85C61.8,52.85 60.88,53.76 60.88,54.88C60.88,56.01 61.8,56.92 62.94,56.92ZM45.06,56.92C46.2,56.92 47.13,56.01 47.13,54.88C47.13,53.76 46.2,52.85 45.06,52.85C43.92,52.85 43,53.76 43,54.88C43,56.01 43.92,56.92 45.06,56.92Z"
+        android:strokeColor="#00000000"
+        android:strokeWidth="1" />
+</vector>