How to add a fast-scroller to the RecyclerView

小开

There are a lot of unanswered questions about RecyclerView and fast-scroll/section indexer, let's try to regroup and gather our opinions and information here.

The short answer is: NO, you can't enable the fast-scroll because RecyclerView does not contain a FastScroller object and nor any related logical-state variables. This because RecyclerView is not an AbsListView.

On the other hand, it's not impossible to implement a RecyclerView which contains a dumped version of FastScroller and the necessary logic for the fast-scrolling, but I have not seen any implementation of this so far.

Please share your consideration about that or if you think I'm wrong.

小开

There is a provision of implementing scroll bars with RecycleView and its LayoutManager.

For example: computeVerticalScrollExtent() , computeVerticalScrollOffset() and computeVerticalScrollRange() can provide information for always positioning a vertical scroll thumb at correct place.

These methods are also there in LayoutManager for delegating actual measurements. So the LayoutManager implementation used must support these measurements.

Also, drag touch on scroll thumb can be intercepted by overriding onInterceptTouchEvent() of RecyclerView. And after calculating the desired scroll, scrollTo() can be called to update RecyclerView.

小开

I stumbled on this question a few days ago when I ran into this situation. Here is my example implementation of FastScroll for RecyclerView:

github.com/danoz73/RecyclerViewFastScroller

Try running the example application, and peruse the code to see a fairly simple usage of a simple RecyclerViewFastScroller widget. There is information on github, but I'll include the basic usage here for a vertical fast scroller.

For a full example, refer to the sample application in the repo.

Basic Usage

In the activity or fragment XML where your RecyclerView resides, include a VerticalRecyclerViewFastScroller object. The following example would be in a relative layout:

...
<android.support.v7.widget.RecyclerView
android:id="@+id/recyclerView"
android:layout_width="match_parent"
android:layout_height="match_parent"/>




<xyz.danoz.recyclerviewfastscroller.vertical.VerticalRecyclerViewFastScroller
android:id="@+id/fast_scroller"
android:layout_width="@dimen/however_wide_you_want_this"
android:layout_height="match_parent"
android:layout_alignParentRight="true"
/>
...

In your fragment or activity where you setup layout programmatically, hook up the fast scroller to the recycler:

...
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.recycler_view_frag, container, false);
...


// Grab your RecyclerView and the RecyclerViewFastScroller from the layout
RecyclerView recyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);
VerticalRecyclerViewFastScroller fastScroller = (VerticalRecyclerViewFastScroller) rootView.findViewById(R.id.fast_scroller);


// Connect the recycler to the scroller (to let the scroller scroll the list)
fastScroller.setRecyclerView(recyclerView);


// Connect the scroller to the recycler (to let the recycler scroll the scroller's handle)
recyclerView.setOnScrollListener(fastScroller.getOnScrollListener());


...
return rootView;
}
...

Hope this helps!

EDIT: There is now added support for Android-Lollipop-Contacts-style section indicators! Check out the sample application's implementation for details.

小开

You can as well use A-Z Fastscroll for RecyclerView. It is the iOS style.

https://github.com/code-computerlove/FastScrollRecyclerView/

How to use it:

Replace android.support.v7.widget.RecyclerView with com.codecomputerlove.fastscrollrecyclerviewdemo.FastScrollRecyclerView
Your adapter needs to implement FastScrollRecyclerViewInterface and override getMapIndex(). The function should return the mapIndex. Look into calculateIndexesForName() for inspiration on how to create it. Once created pass it to the adapter in the constructor.
Create an instance of FastScrollRecyclerViewItemDecoration and add it on your RecyclerView FastScrollRecyclerViewItemDecoration decoration = new FastScrollRecyclerViewItemDecoration(this); mRecyclerView.addItemDecoration(decoration);
add <dimen name="fast_scroll_overlay_text_size">100dp</dimen> to your /values/dimens.xml file. This is the dp size of the overlayed letter

小开

最佳答案

New answer: Over time I've noticed that my original answer had some drawbacks compared to other solutions, especially for fragments within ViewPager.

I suggest to either use the android-x solution in case you don't need a bubble, or a third party library (here is a nice one) in case you do.

old answer:

Since all third party libraries had issues, I've decided to gather what I can find (mostly from here), fix everything and publish my own POC of the fast-scroller of the RecyclerView :

https://github.com/AndroidDeveloperLB/LollipopContactsRecyclerViewFastScroller

usage:

make a RecyclerView.Adapter that implements BubbleTextGetter, which given a position in the data will return the text to show in the bubble-popup.
position the FastScroller inside the layout that container the RecyclerView (probably at the right area).
Customize the FastScroller FastScroller

Some disadvantages:

doesn't support orientation change, but it's probably easy to fix.
doesn't support other layoutManagers. Only LinearLayoutManager
Needs API 11 and above.

Code:

BubbleTextGetter

public interface BubbleTextGetter
{
String getTextToShowInBubble(int pos);
}

recycler_view_fast_scroller__fast_scroller.xml

<?xml version="1.0" encoding="utf-8"?>
<merge xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="wrap_content"
android:layout_height="match_parent">


<TextView
android:id="@+id/fastscroller_bubble"
android:layout_gravity="right|end"
android:gravity="center"
android:textSize="48sp" tools:text="A"
android:layout_width="wrap_content"
android:textColor="#FFffffff"
android:layout_height="wrap_content"
android:background="@drawable/recycler_view_fast_scroller__bubble"
android:visibility="visible"/>


<ImageView
android:id="@+id/fastscroller_handle"
android:layout_width="wrap_content"
android:layout_marginRight="8dp"
android:layout_marginLeft="8dp"
android:layout_height="wrap_content"
android:src="@drawable/recycler_view_fast_scroller__handle"/>


</merge>

MainActivity

...
fastScroller=(FastScroller)findViewById(R.id.fastscroller);
fastScroller.setRecyclerView(recyclerView);

FastScroller

public class FastScroller extends LinearLayout
{
private static final int BUBBLE_ANIMATION_DURATION=100;
private static final int TRACK_SNAP_RANGE=5;


private TextView bubble;
private View handle;
private RecyclerView recyclerView;
private final ScrollListener scrollListener=new ScrollListener();
private int height;


private ObjectAnimator currentAnimator=null;


public FastScroller(final Context context,final AttributeSet attrs,final int defStyleAttr)
{
super(context,attrs,defStyleAttr);
initialise(context);
}


public FastScroller(final Context context)
{
super(context);
initialise(context);
}


public FastScroller(final Context context,final AttributeSet attrs)
{
super(context,attrs);
initialise(context);
}


private void initialise(Context context)
{
setOrientation(HORIZONTAL);
setClipChildren(false);
LayoutInflater inflater=LayoutInflater.from(context);
inflater.inflate(R.layout.recycler_view_fast_scroller__fast_scroller,this,true);
bubble=(TextView)findViewById(R.id.fastscroller_bubble);
handle=findViewById(R.id.fastscroller_handle);
bubble.setVisibility(INVISIBLE);
}


@Override
protected void onSizeChanged(int w,int h,int oldw,int oldh)
{
super.onSizeChanged(w,h,oldw,oldh);
height=h;
}


@Override
public boolean onTouchEvent(@NonNull MotionEvent event)
{
final int action=event.getAction();
switch(action)
{
case MotionEvent.ACTION_DOWN:
if(event.getX()<handle.getX())
return false;
if(currentAnimator!=null)
currentAnimator.cancel();
if(bubble.getVisibility()==INVISIBLE)
showBubble();
handle.setSelected(true);
case MotionEvent.ACTION_MOVE:
setPosition(event.getY());
setRecyclerViewPosition(event.getY());
return true;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_CANCEL:
handle.setSelected(false);
hideBubble();
return true;
}
return super.onTouchEvent(event);
}


public void setRecyclerView(RecyclerView recyclerView)
{
this.recyclerView=recyclerView;
recyclerView.setOnScrollListener(scrollListener);
}


private void setRecyclerViewPosition(float y)
{
if(recyclerView!=null)
{
int itemCount=recyclerView.getAdapter().getItemCount();
float proportion;
if(handle.getY()==0)
proportion=0f;
else if(handle.getY()+handle.getHeight()>=height-TRACK_SNAP_RANGE)
proportion=1f;
else
proportion=y/(float)height;
int targetPos=getValueInRange(0,itemCount-1,(int)(proportion*(float)itemCount));
recyclerView.scrollToPosition(targetPos);
String bubbleText=((BubbleTextGetter)recyclerView.getAdapter()).getTextToShowInBubble(targetPos);
bubble.setText(bubbleText);
}
}


private int getValueInRange(int min,int max,int value)
{
int minimum=Math.max(min,value);
return Math.min(minimum,max);
}


private void setPosition(float y)
{
int bubbleHeight=bubble.getHeight();
int handleHeight=handle.getHeight();
handle.setY(getValueInRange(0,height-handleHeight,(int)(y-handleHeight/2)));
bubble.setY(getValueInRange(0,height-bubbleHeight-handleHeight/2,(int)(y-bubbleHeight)));
}


private void showBubble()
{
AnimatorSet animatorSet=new AnimatorSet();
bubble.setVisibility(VISIBLE);
if(currentAnimator!=null)
currentAnimator.cancel();
currentAnimator=ObjectAnimator.ofFloat(bubble,"alpha",0f,1f).setDuration(BUBBLE_ANIMATION_DURATION);
currentAnimator.start();
}


private void hideBubble()
{
if(currentAnimator!=null)
currentAnimator.cancel();
currentAnimator=ObjectAnimator.ofFloat(bubble,"alpha",1f,0f).setDuration(BUBBLE_ANIMATION_DURATION);
currentAnimator.addListener(new AnimatorListenerAdapter()
{
@Override
public void onAnimationEnd(Animator animation)
{
super.onAnimationEnd(animation);
bubble.setVisibility(INVISIBLE);
currentAnimator=null;
}


@Override
public void onAnimationCancel(Animator animation)
{
super.onAnimationCancel(animation);
bubble.setVisibility(INVISIBLE);
currentAnimator=null;
}
});
currentAnimator.start();
}


private class ScrollListener extends OnScrollListener
{
@Override
public void onScrolled(RecyclerView rv,int dx,int dy)
{
View firstVisibleView=recyclerView.getChildAt(0);
int firstVisiblePosition=recyclerView.getChildPosition(firstVisibleView);
int visibleRange=recyclerView.getChildCount();
int lastVisiblePosition=firstVisiblePosition+visibleRange;
int itemCount=recyclerView.getAdapter().getItemCount();
int position;
if(firstVisiblePosition==0)
position=0;
else if(lastVisiblePosition==itemCount-1)
position=itemCount-1;
else
position=firstVisiblePosition;
float proportion=(float)position/(float)itemCount;
setPosition(height*proportion);
}
}
}

小开

You can try our lib: https://github.com/FutureMind/recycler-fast-scroll. It's still in early development, but was built specifically to deal with smoothness issue we experienced with other libraries. It uses a little bit different mechanism. It supports horizontal LayoutManager as well and will also support multi-column setups in near future.

Edit: there are some neat customisation options now.

小开

The Android Support Library 26.0.0 now supports fastScrollEnabled

New fastScrollEnabled boolean flag for RecyclerView.

If enabled, fastScrollHorizontalThumbDrawable, fastScrollHorizontalTrackDrawable, fastScrollVerticalThumbDrawable, and fastScrollVerticalTrackDrawable must be set.

Sample - https://android.jlelse.eu/fast-scrolling-with-recyclerview-2b89d4574688

小开

FastScroller functionality is added from android library 26.0.0 for RecyclerView

compile dependency

    compile 'com.android.support:recyclerview-v7:26.1.0'
compile 'com.android.support:design:26.1.0'

add depedency to project.gradle

     maven {
url "https://maven.google.com"
}

your recyclerview.xml file

    <?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
xmlns:tool="http://schemas.android.com/tools"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:orientation="vertical"
tool:context=".MainActivity">
<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/songlist"
android:layout_marginStart="8dp"
android:layout_marginEnd="8dp"
app:fastScrollEnabled="true"
app:fastScrollVerticalThumbDrawable="@drawable/thumb_drawable"
app:fastScrollVerticalTrackDrawable="@drawable/line_drawable"
app:fastScrollHorizontalThumbDrawable="@drawable/thumb_drawable"
app:fastScrollHorizontalTrackDrawable="@drawable/line_drawable"
/></LinearLayout>

thumb.xml

   <?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">


<corners
android:topLeftRadius="44dp"
android:topRightRadius="44dp"
android:bottomLeftRadius="44dp"
android:bottomRightRadius="44dp" />


<padding
android:paddingLeft="22dp"
android:paddingRight="22dp" />


<solid android:color="#f73831" />


</shape>

line.xml

    <?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">


<solid android:color="@color/dark_grey" />


<padding
android:top="10dp"
android:left="10dp"
android:right="10dp"
android:bottom="10dp"/>
</shape>

thumb_drawable.xml

    <?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/thumb"
android:state_focused="true"
android:state_pressed="true" />


<item android:drawable="@drawable/thumb"
android:state_focused="false"
android:state_pressed="true" />
<item android:drawable="@drawable/thumb"
android:state_focused="true" />
<item android:drawable="@drawable/thumb"
android:state_focused="false"
android:state_pressed="false" />
</selector>

line_drawble.xml

    <?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
<item android:drawable="@drawable/line"
android:state_focused="true"
android:state_pressed="true" />


<item android:drawable="@drawable/line"
android:state_focused="false"
android:state_pressed="true" />
<item android:drawable="@drawable/line"
android:state_focused="true" />
<item android:drawable="@drawable/line"
android:state_focused="false"
android:state_pressed="false" />
</selector>

小开

Just enable fast scrolling and add thumb, tracker for scroll bar like below.

<android.support.v7.widget.RecyclerView
android:id="@+id/rv_sensors"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:fastScrollEnabled="true"
app:fastScrollHorizontalThumbDrawable="@drawable/thumb_drawable"
app:fastScrollHorizontalTrackDrawable="@drawable/line_drawable"
app:fastScrollVerticalThumbDrawable="@drawable/thumb_drawable"
app:fastScrollVerticalTrackDrawable="@drawable/line_drawable" />

小开

This new library was based on framework launcher's fast scroller: https://github.com/zhanghai/AndroidFastScroll

Usage:

new FastScrollerBuilder(recyclerView).build();

Optionally implement PopupTextProvider in the adapter.

小开

The fast-scroller in android studio is still very buggy as it's only based on xml,so I went digging for external libraries that could implement fast scrolling. You can get it here. Very easy to implement and customize.

How to add a fast-scroller to the RecyclerView

Background

The problem

The question

github.com/danoz73/RecyclerViewFastScroller

Basic Usage