Mise en place d'une collapsing toolbar

Bonjour,

Je suis en train de developper une application disposant de 3 activités dont 2 avec une toolbar classique, et la 3 ième avec une collapsing toolbar. voici mes sources :
le fichier manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.openclassrooms.entrevoisins">

    <uses-permission android:name="android.permission.INTERNET" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:networkSecurityConfig="@xml/network_security_config"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        >

        <activity
            android:name=".ui.neighbour_list.AddNeighbourActivity"
            android:label="@string/activity_new_neighbour"
            android:theme="@style/AppTheme" />

        <activity
            android:name=".ui.neighbour_list.ZoomNeighbourActivity"
            android:theme="@style/AppThemeNoToolBar" />

        <activity
            android:name=".ui.neighbour_list.ListNeighbourActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>

</manifest>

Le fichier "style.xml"

<resources>

    <!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.MaterialComponents.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>

    </style>

    <style name="AppThemeNoToolBar" parent="Theme.AppCompat.Light.NoActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
    </style>
    <style name="AppTheme.AppBarOverlay" parent="ThemeOverlay.AppCompat.Dark.ActionBar" />

    <style name="AppTheme.PopupOverlay" parent="ThemeOverlay.AppCompat.Light" />

</resources>

Mon fichier layout avec la collapsing toolbar

<?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:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context=".ui.neighbour_list.ZoomNeighbourActivity">

    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_zoom"
        android:layout_width="match_parent"
        android:layout_height="300dp"
        android:fitsSystemWindows="true"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/toolbar_layout_zoom"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed"
            app:toolbarId="@+id/toolbarZoom">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@color/colorAccent"
                android:orientation="vertical"
                app:layout_collapseMode="parallax"
                app:layout_scrollFlags="scroll|exitUntilCollapsed">

                <ImageView
                    android:id="@+id/zoom_avatar"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    />

                <TextView
                    android:id="@+id/zoom_name"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_gravity="center"
                    android:layout_marginTop="5dp"
                    android:textColor="@color/white"/>

            </LinearLayout>

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:navigationIcon="@drawable/ic_baseline_arrow_back_24"
                app:popupTheme="@style/AppTheme.PopupOverlay"/>

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


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

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/floating_action"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="5dp"
        android:src="@drawable/ic_baseline_star_border_24"
        app:backgroundTint="@color/white"
        app:layout_anchor="@id/app_bar_zoom"
        app:layout_anchorGravity="bottom|end"/>

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

et la classe java associée à l'activité avec collapsing toolbar

package com.openclassrooms.entrevoisins.ui.neighbour_list;

import android.os.Bundle;
import android.support.design.widget.AppBarLayout;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import com.bumptech.glide.Glide;
import com.openclassrooms.entrevoisins.R;
import com.openclassrooms.entrevoisins.model.Neighbour;

public class ZoomNeighbourActivity extends AppCompatActivity {
    private ImageView mZoomAvatar;
    private TextView mZoomNom;
    Toolbar toolbarZoom;
    Menu zoom_menu;
    AppBarLayout appBarLayoutZoom;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate( savedInstanceState );
        setContentView( R.layout.activity_zoom_neighbour );
        Neighbour neighbour = (Neighbour) getIntent().getSerializableExtra( "NEIGHBOUR" );
        Log.e( "TAG3", "nom : " + neighbour.getName() );

        mZoomAvatar = findViewById( R.id.zoom_avatar );
        Glide.with( this )
                .load( neighbour.getAvatarUrl() )
                .into( mZoomAvatar );

        appBarLayoutZoom = findViewById( R.id.app_bar_zoom );
        toolbarZoom = findViewById( R.id.toolbarZoom );
        setSupportActionBar( toolbarZoom );

        getSupportActionBar().setDisplayShowTitleEnabled( false );

        toolbarZoom.setNavigationOnClickListener( new View.OnClickListener(){
            @Override
            public void onClick(View v) {
                finish();
            }
        } );
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        this.zoom_menu = menu;
        getMenuInflater().inflate( R.menu.zoom_menu, menu );
        hideShowFAB();
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();
        if (id == R.id.favorit_zoom) {
            return true;
        }
        return super.onOptionsItemSelected( item );
    }

    public void hideShowFAB(){
        appBarLayoutZoom.addOnOffsetChangedListener( new AppBarLayout.OnOffsetChangedListener(){
            @Override
            public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
                MenuItem menuItem = zoom_menu.findItem( R.id.favorit_zoom );
                if (Math.abs( verticalOffset ) == appBarLayout.getTotalScrollRange()) {
                    menuItem.setVisible( true );
                } else if (verticalOffset == 0) {
                    menuItem.setVisible( false );
                }
            }
        } );

    }
}

A l'execution je plante avec le message :

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.openclassrooms.entrevoisins/com.openclassrooms.entrevoisins.ui.neighbour_list.ZoomNeighbourActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.app.ActionBar.setDisplayShowTitleEnabled(boolean)' on a null object reference

Merci d'avance pour votre aide...



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