I am trying to use both AppBarLayout
and BottomNavigationLayout
in a single CoordinatorLayout
and I'm having difficulties hiding the BottomNavigationLayout
as required by the material guideline.
I mean something like this:
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="false">
<android.support.design.widget.AppBarLayout
android:id="@+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_insetEdge="top"
android:theme="@style/AppTheme.AppBarOverlay">
<android.support.v7.widget.Toolbar
android:id="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
app:popupTheme="@style/AppTheme.PopupOverlay"
app:layout_scrollFlags="scroll|enterAlways"/>
</android.support.design.widget.AppBarLayout>
<android.support.design.widget.BottomNavigationView
android:id="@+id/bottom_nav"
android:layout_width="match_parent"
android:layout_height="56dp"
android:layout_gravity="bottom"
app:menu="@menu/menu_bottom_navigation"/>
<FrameLayout
android:id="@+id/content_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="top"
app:layout_behavior="@string/appbar_scrolling_view_behavior"/>
</android.support.design.widget.CoordinatorLayout>
As you can see, I also have a FrameLayout
that's used to contain a fragment with the actual content. Currently there are no default/built-in behaviors for the BottomNavigationView
- neither for the view itself, nor for its siblings. The existing appbar_scrolling_view_behavior
handles the content view in coordination with the appbar but ignores other siblings.
I am looking for a solution to hide and show both the appbar and the bottom navigation view on scroll.
After a day or two of searching I settled with a custom Behavior
attached to the BottomNavigationView
. Its main idea is to detect when the BottomNavigationView's sibling is scrolled so that it can hide the BottomNavigationView. Something like this:
public class BottomNavigationBehavior extends CoordinatorLayout.Behavior<BottomNavigationView> {
public BottomNavigationBehavior() {
super();
}
public BottomNavigationBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public boolean layoutDependsOn(CoordinatorLayout parent, BottomNavigationView child, View dependency) {
boolean dependsOn = dependency instanceof FrameLayout;
return dependsOn;
}
@Override
public boolean onStartNestedScroll(CoordinatorLayout coordinatorLayout, BottomNavigationView child, View directTargetChild, View target, int nestedScrollAxes) {
return nestedScrollAxes == ViewCompat.SCROLL_AXIS_VERTICAL;
}
@Override
public void onNestedPreScroll(CoordinatorLayout coordinatorLayout, BottomNavigationView child, View target, int dx, int dy, int[] consumed) {
if(dy < 0) {
showBottomNavigationView(child);
}
else if(dy > 0) {
hideBottomNavigationView(child);
}
}
private void hideBottomNavigationView(BottomNavigationView view) {
view.animate().translationY(view.getHeight());
}
private void showBottomNavigationView(BottomNavigationView view) {
view.animate().translationY(0);
}
}
As you can see, I'm using simple ViewPropertyAnimator
, obtained using the child views's animate
method. This leads to a simple animation that doesn't really match the AppBarLayout
's behavior but it's decent enough to look good and at the same time it's simple enough to implement.
I expect that at some point the Android team will add a default Behavior for the BottomNavigationView in the support library so I don't think it's reasonable to invest a lot more time to exactly duplicate the AppBarLayout's behavior.
edit (April 2018): see the comments section for a minor clarification about onStartNestedScroll
and onNestedPreScroll
and their new versions.