How to make toolbar visible again which is previous hidden using layout_scrollFlags, when swipe to different viewpager page [duplicate]

Question

Currently, I have the following page with ViewPager

When the page in INFO tab is scrolled, toolbar will be hidden. This behavior is implemented via CoordinatorLayout, AppBarLayout and app:layout_scrollFlags

<?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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">


    <android.support.design.widget.AppBarLayout
        android:id="@+id/app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:elevation="0dp"
        android:elevation="0dp"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" >

        <android.support.v7.widget.Toolbar
            app:layout_scrollFlags="scroll|enterAlways|snap"

            android:id="@+id/toolbar"
            android:layout_height="wrap_content"
            android:layout_width="match_parent"
            android:minHeight="?attr/actionBarSize"
            android:background="@android:color/transparent"
            app:elevation="0dp"
            android:elevation="0dp"
            app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

        <android.support.design.widget.TabLayout
            android:id="@+id/tab_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tabIndicatorColor="?attr/detailedStockTabIndicatorColor" />
    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/view_pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

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

So, this is how it looks like after scrolling.

After Scroll, Toolbar is hidden

Since this is a ViewPager, if I swipe to FINANCIAL tab, it will look like the following.

Followed by Swipe

Since, the page in FINANCIAL tab is not scroll-able, we hope not to hide the Toolbar.

I was wondering, how to make toolbar visible again which is previous hidden using layout_scrollFlags, when swipe to different ViewPager page?

Answer 1

you can do it like this :

final AppBarLayout appBarLayout = view.findViewById(R.id.app_bar_layout);
    viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
            if (position == 1)
                appBarLayout.setExpanded(true, true);
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });

so when viewPager is in unscrollable page it expands and toolbar appears

Answer 2

@Marzieh Heidari answer is the correct answer for this question, but I share my different approach that I use in my project to solve this problem.

In the fragment which have short content, I still keep NestedScrollView at root. Then I still able to scroll up/down to collapse and expand toolbar

<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.NestedScrollView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    android:isScrollContainer="false"
    >
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        >
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="This fragment have short content"
            android:textSize="100sp"
            />
    </LinearLayout>
</android.support.v4.widget.NestedScrollView>

Hope it help