android - changing Textview dinamically

Question

I am new to android app. I am following a book to change the text dynamically, but it doesn't do what it is supposed to do. I have researched, but I couldn't find where is the problem. the app works find but don't change the text. I am stuck and I would really apreciate some help.

Java file:

public class ViewDVDActivity extends  Activity {

    TextView txtTituloDVD;
    TextView txtAnyoDVD;
    TextView txtActor1;
    TextView txtActor2;
    TextView txtResumenPelicula;

    @Override
    protected void onCreate ( Bundle saveInstanceState ) {
        super.onCreate(saveInstanceState);
        // asignacion layout
        setContentView(R.layout.activity_viewdvd);

        // obtención componentes
        txtTituloDVD = (TextView) findViewById(R.id.tituloDVD);
        txtAnyoDVD = (TextView) findViewById(R.id.anyoDVD);
        txtActor1 = (TextView) findViewById(R.id.actor1);
        txtActor2 = (TextView) findViewById(R.id.actor2);
        txtResumenPelicula = (TextView) findViewById(R.id.resumenPelicula);

    }

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

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

          txtTituloDVD.setText("Matrix");
          txtAnyoDVD.setText(String.format(getString(R.string.anyo_de_aparicion), 2014));
          txtActor1.setText("Nelson Harris");
          txtActor2.setText("Brian Eno");
          String resumen = "En un lugar de la mancha de cuyo nombre no me acuerdo";
          txtResumenPelicula.setText(resumen);
      }

manifest.xml file:

<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/Theme.LocDVD">
            <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=".ViewDVDActivity">
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
        </application>

xml file: activity_viewdvd.xml

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

     <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal|top"
        android:layout_marginTop="16dp"
        android:layout_weight="1"
        android:text="TextView"  /> 
    <TextView
        android:id="@+id/tituloDVD"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Título del dvd"
        android:layout_gravity="top|center_horizontal"
        android:layout_marginTop="16dp"
        android:textSize="22sp"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:text="A?o"
        android:textSize="15sp"
        android:id="@+id/anyoDVD" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:textSize="18sp"
        android:text="Actor 1"
        android:id="@+id/actor1" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:textSize="18sp"
        android:text="Actor 2"
        android:id="@+id/actor2" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="16dp"
        android:textSize="18sp"
        android:text="Resumen"
        android:minLines="5"
        android:maxLines="15"
        android:id="@+id/resumenPelicula" />

</LinearLayout>

String values:

<resources>
    <string name="app_name">LocDVD</string>
    <string name="anyo_de_aparicion">"A?o de aparición : %d"</string>
    <string name="titulo_de_la_pelicula">"Títlo de la película"</string>
    <string name="anyo_de_aparicion_etiqueta">"A?o de aparición"</string>
    <string name="actores">"Actores"</string>
    <string name="resumen">"Resumen"</string>
</resources>

Answer 1

I think you navigate to wrong activity

<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/Theme.LocDVD">
            <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=".ViewDVDActivity">
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
        </application>

because you have two luncher activity

if you want to show ViewDVDActivity at first

<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/Theme.LocDVD">
            <activity android:name=".MainActivity">
               
            </activity>
            <activity android:name=".ViewDVDActivity">
                <intent-filter>
                    <action android:name="android.intent.action.MAIN" />
                    <category android:name="android.intent.category.LAUNCHER" />
                </intent-filter>
            </activity>
        </application>