Hiding toolbar and tablayout from a particular fragment in a viewpager

Question

I use a single activity with four Fragments . Fragments 1 , 2 and 3 are Viewpager Fragments and fragment 4 is a Detail Fragment that replaces fragment 3 when a list item is clicked. Unfortunately when the detail fragment replaces the master fragment it adds a Toolbar and back button in addition to the existing toolbar and Tablayout . However, I'd like to replace the existing toolbar and tablayout with this instead.

QUESTION : How would I achieve this without creating a new activity?

Master fragment. Has desired toolbar and tablayout.

Details fragment. Has both new toolbar (desired) and original toolbar and tablayout (undesired)

MainActivity.XML

<?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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    <android.support.v7.widget.Toolbar
        android:id="@+id/toolbar"
        android:layout_width="match_parent"
        android:layout_height="?attr/actionBarSize"
        android:background="?attr/colorPrimary"
        app:layout_scrollFlags="scroll|enterAlways"
        app:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

    <android.support.design.widget.TabLayout
        android:id="@+id/tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:tabMode="fixed"
        app:tabGravity="fill"/>

    <android.support.v4.view.ViewPager
        android:id="@+id/pager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        android:background="@color/black_process_2"/>

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

DetailFragment.XML

<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:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"
tools:context="com.allison.viewpagermasterdetail.ItemDetailActivity"
tools:ignore="MergeRootFrame">

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

    <android.support.design.widget.CollapsingToolbarLayout
        android:id="@+id/toolbar_layout"
        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/toolbar">

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

        </android.support.v7.widget.Toolbar>

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

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

<android.support.v4.widget.NestedScrollView
    android:id="@+id/item_detail_container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

    <TextView
        android:id="@+id/item_detail"
        style="?android:attr/textAppearanceLarge"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="16dp"
        android:textIsSelectable="true"/>

</android.support.v4.widget.NestedScrollView>

<android.support.design.widget.FloatingActionButton
    android:id="@+id/fab"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center_vertical|start"
    android:layout_margin="@dimen/fab_margin"
    android:src="@android:drawable/stat_notify_chat"
    app:layout_anchor="@+id/item_detail_container"
    app:layout_anchorGravity="top|end" />

Answer 1

When you open details fragment invoke:

toolbar.setVisibility(View.GONE);
tabLayout.setVisibility(View.GONE);

and

@Override
public void onBackPressed() {
    if (currentFragment instanceOf DetailFragment) {
      toolbar.setVisibility(View.VISIBILE);
      tabLayout.setVisibility(View.VISIBLE);
    }
    ...
}

Answer 2

Well i personally think that the best solution is to open the detail in a separate activity with it's own toolbar. This solution would be the easiest and the cleanest in my opinion.

If you would go for the detail fragment i would suggest you to set toolbar in the activity via setSupportActionBar() and modify it within the fragment with getSupportActionBar() method.