Disable expanding of AppBarLayout

Question

I have a Toolbar together with a TabLayout and an image wrapped inside a CollapsingToolbarLayout. This gif pretty much sums it up:

https://raw.githubusercontent.com/vitovalov/TabbedCoordinatorLayout/master/art/demo.gif

This is the 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:fitsSystemWindows="true">

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

        <android.support.design.widget.CollapsingToolbarLayout
            android:id="@+id/collapse_toolbar"
            android:layout_width="match_parent"
            android:layout_height="250dp"
            android:fitsSystemWindows="true"
            app:contentScrim="?attr/colorPrimary"
            app:layout_scrollFlags="scroll|exitUntilCollapsed">

            <ImageView
                android:id="@+id/header"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                android:background="@drawable/photo"
                android:fitsSystemWindows="true"
                android:scaleType="centerCrop"
                app:layout_collapseMode="parallax"/>

            <android.support.v7.widget.Toolbar
                android:id="@+id/toolbar"
                android:layout_width="match_parent"
                android:layout_height="100dp"
                android:gravity="top"
                android:minHeight="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
                app:titleMarginTop="15dp"/>

            <android.support.design.widget.TabLayout
                android:id="@+id/tabs"
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                android:layout_gravity="bottom"
                app:tabIndicatorColor="@color/colorAccent"/>

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

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

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

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

What I want to achieve is that for instance on Tab 2 I don't want to let the user be able to see the image. So even if he tries to pull the AppBarLayout down he should not see the image under any circumstance.

Calling appBarLayout.setExpanded(false); upon showing Tab 2 does hide the image and collapse everything back. Though the moment you press on the AppBarLayout and swipe down you can get the image back. This should not be the case.

How can I prevent this behavior?

I'm using v23.1.1 of the support libraries. For version 22 of the libraryes there's already this question. The workaround is however no longer applicable with version 23.

Answer 1

The trick provided by Anne-Claire works, but you end up loosing the animation. What I did instead was to create a custom Behavior extending the AppBarLayout.Behavior class that would allow me to enable/disable the scrolling whenever I chose.

public class CustomAppBarLayoutBehavior extends AppBarLayout.Behavior {

    private boolean shouldScroll = false;

    public CustomAppBarLayoutBehavior(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    public boolean onStartNestedScroll(CoordinatorLayout parent, AppBarLayout child, View directTargetChild, View target, int nestedScrollAxes, int type) {
        return shouldScroll;
    }

    @Override
    public boolean onTouchEvent(CoordinatorLayout parent, AppBarLayout child, MotionEvent ev) {
        if(shouldScroll){
            return super.onTouchEvent(parent, child, ev);
        }else{
            return false;
        }
    }

    public void setScrollBehavior(boolean shouldScroll){
        this.shouldScroll = shouldScroll;
    }

    public boolean isShouldScroll(){
        return shouldScroll;
    }
}

You should then apply this behavior to your AppBarLayout in the xml layout

<android.support.design.widget.AppBarLayout
    android:id="@+id/app_bar_layout"
    android:layout_width="wrap_content"
    android:layout_height="@dimen/activity_main_toolbar_height_extended"
    android:theme="@style/ThemeOverlay.AppCompat.Dark"
    android:fitsSystemWindows="true"
    android:elevation="4dp"
    app:layout_behavior="io.eighttails.mvp.widgets.CustomAppBarLayoutBehavior">

And then you'll be able to switch it on and off as you please by doing:

CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) mAppBarLayout.getLayoutParams();
((CustomAppBarLayoutBehavior)layoutParams.getBehavior()).setScrollBehavior(true);

or

CoordinatorLayout.LayoutParams layoutParams = (CoordinatorLayout.LayoutParams) mAppBarLayout.getLayoutParams();
((CustomAppBarLayoutBehavior)layoutParams.getBehavior()).setScrollBehavior(false);