Expand/Collapse Lollipop toolbar animation (Telegram app)

Edit :

Since the release of the Android Design support library, there's an easier solution. Check joaquin's answer

--

Here's how I did it, there probably are many other solutions but this one worked for me.

1. First of all, you have to use a Toolbar with a transparent background. The expanding & collapsing Toolbar is actually a fake one that's under the transparent Toolbar. (you can see on the first screenshot below - the one with the margins - that this is also how they did it in Telegram).

   We only keep the actual Toolbar for the NavigationIcon and the overflow MenuItem.

   

2. Everything that's in the red rectangle on the second screenshot (ie the fake Toolbar and the FloatingActionButton) is actually a header that you add to the settings ListView (or ScrollView).

   So you have to create a layout for this header in a separate file that could look like this :

    <!-- The headerView layout. Includes the fake Toolbar & the FloatingActionButton -->
   
   
   <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:layout_width="match_parent"
   android:layout_height="wrap_content">
   
   
   <RelativeLayout
   android:id="@+id/header_container"
   android:layout_width="match_parent"
   android:layout_height="@dimen/header_height"
   android:layout_marginBottom="3dp"
   android:background="@android:color/holo_blue_dark">
   
   
   <RelativeLayout
   android:id="@+id/header_infos_container"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:layout_alignParentBottom="true"
   android:padding="16dp">
   
   
   <ImageView
   android:id="@+id/header_picture"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_centerVertical="true"
   android:layout_marginRight="8dp"
   android:src="@android:drawable/ic_dialog_info" />
   
   
   <TextView
   android:id="@+id/header_title"
   style="@style/TextAppearance.AppCompat.Title"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_toRightOf="@+id/header_picture"
   android:text="Toolbar Title"
   android:textColor="@android:color/white" />
   
   
   <TextView
   android:id="@+id/header_subtitle"
   style="@style/TextAppearance.AppCompat.Subhead"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_below="@+id/header_title"
   android:layout_toRightOf="@+id/header_picture"
   android:text="Toolbar Subtitle"
   android:textColor="@android:color/white" />
   
   
   </RelativeLayout>
   </RelativeLayout>
   
   
   <FloatingActionButton
   android:id="@+id/header_fab"
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:layout_gravity="bottom|right"
   android:layout_margin="10dp"
   android:src="@drawable/ic_open_in_browser"/>
   
   
   </FrameLayout>
   

   (Note that you can use negative margins/padding for the fab to be straddling on 2 Views)

3. Now comes the interesting part. In order to animate the expansion of our fake Toolbar, we implement the ListView onScrollListener.

   // The height of your fully expanded header view (same than in the xml layout)
   int headerHeight = getResources().getDimensionPixelSize(R.dimen.header_height);
   // The height of your fully collapsed header view. Actually the Toolbar height (56dp)
   int minHeaderHeight = getResources().getDimensionPixelSize(R.dimen.action_bar_height);
   // The left margin of the Toolbar title (according to specs, 72dp)
   int toolbarTitleLeftMargin = getResources().getDimensionPixelSize(R.dimen.toolbar_left_margin);
   // Added after edit
   int minHeaderTranslation;
   
   
   private ListView listView;
   
   
   // Header views
   private View headerView;
   private RelativeLayout headerContainer;
   private TextView headerTitle;
   private TextView headerSubtitle;
   private FloatingActionButton headerFab;
   
   
   
   
   @Override
   public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
   {
   View rootView = inflater.inflate(R.layout.listview_fragment, container, false);
   listView = rootView.findViewById(R.id.listview);
   
   
   // Init the headerHeight and minHeaderTranslation values
   
   
   headerHeight = getResources().getDimensionPixelSize(R.dimen.header_height);
   minHeaderTranslation = -headerHeight +
   getResources().getDimensionPixelOffset(R.dimen.action_bar_height);
   
   
   // Inflate your header view
   headerView = inflater.inflate(R.layout.header_view, listview, false);
   
   
   // Retrieve the header views
   headerContainer = (RelativeLayout) headerView.findViewById(R.id.header_container);
   headerTitle = (TextView) headerView.findViewById(R.id.header_title);
   headerSubtitle = (TextView) headerView.findViewById(R.id.header_subtitle);
   headerFab = (TextView) headerView.findViewById(R.id.header_fab);;
   
   
   // Add the headerView to your listView
   listView.addHeaderView(headerView, null, false);
   
   
   // Set the onScrollListener
   listView.setOnScrollListener(this);
   
   
   // ...
   
   
   return rootView;
   }
   
   
   @Override
   public void onScrollStateChanged(AbsListView view, int scrollState)
   {
   // Do nothing
   }
   
   
   
   
   @Override
   public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
   {
   Integer scrollY = getScrollY(view);
   
   
   // This will collapse the header when scrolling, until its height reaches
   // the toolbar height
   headerView.setTranslationY(Math.max(0, scrollY + minHeaderTranslation));
   
   
   // Scroll ratio (0 <= ratio <= 1).
   // The ratio value is 0 when the header is completely expanded,
   // 1 when it is completely collapsed
   float offset = 1 - Math.max(
   (float) (-minHeaderTranslation - scrollY) / -minHeaderTranslation, 0f);
   
   
   
   
   // Now that we have this ratio, we only have to apply translations, scales,
   // alpha, etc. to the header views
   
   
   // For instance, this will move the toolbar title & subtitle on the X axis
   // from its original position when the ListView will be completely scrolled
   // down, to the Toolbar title position when it will be scrolled up.
   headerTitle.setTranslationX(toolbarTitleLeftMargin * offset);
   headerSubtitle.setTranslationX(toolbarTitleLeftMargin * offset);
   
   
   // Or we can make the FAB disappear when the ListView is scrolled
   headerFab.setAlpha(1 - offset);
   }
   
   
   
   
   // Method that allows us to get the scroll Y position of the ListView
   public int getScrollY(AbsListView view)
   {
   View c = view.getChildAt(0);
   
   
   if (c == null)
   return 0;
   
   
   int firstVisiblePosition = view.getFirstVisiblePosition();
   int top = c.getTop();
   
   
   int headerHeight = 0;
   if (firstVisiblePosition >= 1)
   headerHeight = this.headerHeight;
   
   
   return -top + firstVisiblePosition * c.getHeight() + headerHeight;
   }
   

Note that there are some parts of this code I didn't test, so feel free to highlight mistakes. But overall, I'm know that this solution works, even though I'm sure it can be improved.

EDIT 2:

There were some mistakes in the code above (that I didn't test until today...), so I changed a few lines to make it work :

1. I introduced another variable, minHeaderTranslation, which replaced minHeaderHeight;

2. I changed the Y translation value applied to the header View from :

       headerView.setTranslationY(Math.max(-scrollY, minHeaderTranslation));
   

   to :

       headerView.setTranslationY(Math.max(0, scrollY + minHeaderTranslation));
   

   Previous expression wasn't working at all, I'm sorry about that...

3. The ratio calculation also changed, so that it now evolves from the bottom the toolbar (instead of the top of the screen) to the full expanded header.

This is my implementation:

collapsedHeaderHeight and expandedHeaderHeight are defined somewhere else, with the function getAnimationProgress I can get the Expand/Collapse progress, base on this value I do my animation and show/hide the real header.

  listForumPosts.setOnScrollListener(new AbsListView.OnScrollListener() {


/**
* @return [0,1], 0 means header expanded, 1 means header collapsed
*/
private float getAnimationProgress(AbsListView view, int firstVisibleItem) {
if (firstVisibleItem > 0)
return 1;


// should not exceed 1
return Math.min(
-view.getChildAt(0).getTop() / (float) (expandedHeaderHeight - collapsedHeaderHeight), 1);
}


@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
// at render beginning, the view could be empty!
if (view.getChildCount() > 0) {
float animationProgress = getAnimationProgress(view, firstVisibleItem);
imgForumHeaderAvatar.setAlpha(1-animationProgress);
if (animationProgress == 1) {
layoutForumHeader.setVisibility(View.VISIBLE);
} else {
layoutForumHeader.setVisibility(View.GONE);
}
}
}


@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// do nothing
}


}

Also check out CollapsingTitleLayout written by Chris Banes in Android team: https://plus.google.com/+ChrisBanes/posts/J9Fwbc15BHN

Code: https://gist.github.com/chrisbanes/91ac8a20acfbdc410a68

Use design support library http://android-developers.blogspot.in/2015/05/android-design-support-library.html

include this in build.gradle

compile 'com.android.support:design:22.2.0'
compile 'com.android.support:appcompat-v7:22.2.+'

for recycler view include this also

compile 'com.android.support:recyclerview-v7:22.2.0'

    <!-- AppBarLayout allows your Toolbar and other views (such as tabs provided by TabLayout)
to react to scroll events in a sibling view marked with a ScrollingViewBehavior.-->
<android.support.design.widget.AppBarLayout
android:id="@+id/appbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true">


<!-- specify tag app:layout_scrollFlags -->
<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"/>


<!-- specify tag app:layout_scrollFlags -->
<android.support.design.widget.TabLayout
android:id="@+id/tabLayout"
android:scrollbars="horizontal"
android:layout_below="@+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways"/>


<!--  app:layout_collapseMode="pin" will help to pin this view at top when scroll -->
<TextView
android:layout_width="match_parent"
android:layout_height="50dp"
android:text="Title"
android:gravity="center"
app:layout_collapseMode="pin" />


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


<!-- This will be your scrolling view.
app:layout_behavior="@string/appbar_scrolling_view_behavior" tag connects this features -->
<android.support.v7.widget.RecyclerView
android:id="@+id/list"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
android:layout_width="match_parent"
android:layout_height="match_parent">


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


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

Your activity should extend AppCompatActivity

public class YourActivity extends AppCompatActivity {


@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.your_layout);


//set toolbar
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
}


}

Your app theme should be like this

    <resources>
<!-- Base application theme. -->
<style name="AppTheme" parent="Theme.AppCompat.NoActionBar">
</style>
</resources>