Fragment内的CollapsingToolbarLayout返回null

Question

I have a viewpager inside in a activity. This activity launch three fragements (not tabbed), as created three different class extends fragment. It is working fine with horizontal scrolling in between fragment. Now I want to use collapsingToolbar with separate image display in fragment. Activity - having viewpager, Fragment1 XML having collapsingToolbar, Fragement1 also have 'content_launch.xml' Fragement1 class - toolbar added but while fetching (CollapsingToolbar object it is returning null.

Activity XML as below :

<LinearLayout 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:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" tools:context=".activity.LaunchActivity">

<android.support.v4.view.ViewPager
android:id="@+id/launchpager"
android:layout_width="match_parent"
android:layout_height="0px"
android:layout_weight="1" app:layout_behavior="@string/appbar_scrolling_view_behavior"/>
</LinearLayout>

Activity Class to launch viewpager

ViewPager viewPager = (ViewPager) findViewById(R.id.launchpager);
viewPager.setAdapter(new LaunchAdapter(getSupportFragmentManager
(),getApplicationContext()));

Fragement1 XML

<android.support.design.widget.CoordinatorLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/quote_coordinator"
    android:layout_height="match_parent"
    android:layout_width="match_parent"
        android:background="@android:color/white"
        android:fitsSystemWindows="true">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="@dimen/detail_backdrop_height"
        android:id="@+id/quote_appbar"
        android:fitsSystemWindows="true"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/quote_collapsing_toolbar"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:fitsSystemWindows="true"
            app:contentScrim ="?attr/colorPrimary"
            app:expandedTitleMarginEnd="64dp"
            app:expandedTitleMarginStart="48dp"
            app:expandedTitleTextAppearance="@android:color/transparent"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <RelativeLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">

                <ImageView android:id="@+id/quote_backdrop"
                    android:layout_width="match_parent"
                    android:layout_height="match_parent"
                    android:fitsSystemWindows="true"
                    android:scaleType="centerCrop"
                    app:layout_collapseMode ="parallax"/>
                <LinearLayout
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_centerInParent="true"
                    android:gravity="center_horizontal" android:orientation="vertical">

                    <TextView android:id="@+id/quote_main_title"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="@string/main_title"
                        android:textColor="@android:color/white"
                        android:textSize="@dimen/main_title"/>

                    <TextView android:id="@+id/quote_sub_title"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content"
                        android:text="@string/main_sub_title"
                        android:textColor="@android:color/white"
                        android:textSize="@dimen/main_sub_title"/>

                </LinearLayout>

            </RelativeLayout>

            <android.support.v7.widget.Toolbar
                android:id="@+id/quote_toolbar"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>


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


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

    <include layout="@layout/content_quote"/>
</android.support.design.widget.CoordinatorLayout>

Fragment1 Class:

public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Toolbar quoteToolbar = (Toolbar) getActivity().findViewById(R.id.quote_toolbar);
    ((AppCompatActivity) getActivity()).setSupportActionBar(quoteToolbar);
final CollapsingToolbarLayout collapsingToolbar = (CollapsingToolbarLayout) getActivity().findViewById(R.id.quote_collapsing_toolbar);
}

collapsingToolbar object returned as null, not able to find any suggestions, can someone suggest possible way to get object..

Answer 1

First thing: you should not use onCreate to initialize view elements in fragment, you should use onCreateView instead. Second one you don't use getActivity() context.

So instead of this code:

public void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Toolbar quoteToolbar = (Toolbar) getActivity().findViewById(R.id.quote_toolbar);
    ((AppCompatActivity) getActivity()).setSupportActionBar(quoteToolbar);
final CollapsingToolbarLayout collapsingToolbar = (CollapsingToolbarLayout) getActivity().findViewById(R.id.quote_collapsing_toolbar);
}

use this:

@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container,
                                     @Nullable Bundle savedInstanceState) {
// inflate your layout.    
View view = inflater.inflate(R.layout.yourlayout, container, false);
Toolbar quoteToolbar = (Toolbar) view.findViewById(R.id.quote_toolbar);
((AppCompatActivity) view).setSupportActionBar(quoteToolbar);
            final CollapsingToolbarLayout collapsingToolbar = (CollapsingToolbarLayout) view.findViewById(R.id.quote_collapsing_toolbar);

return view
}

Best regards and happy new year! :)