Detect end of ScrollView

Question

I have an app, that has an Activity that uses a ScrollView. I need to detect when user gets to the bottom of the ScrollView. I did some googleing and I found this page where is explained. But, in the example, that guys extends ScrollView. As I said, I need to extend Activity.

So, I said "ok, let's try to make a custom class extending ScrollView, override the onScrollChanged() method, detect the end of the scroll, and act accordingly".

I did, but in this line:

scroll = (ScrollViewExt) findViewById(R.id.scrollView1);

it throws a java.lang.ClassCastException. I changed the <ScrollView> tags in my XML but, obviously, it doesn't work. My questions are: Why, if ScrollViewExt extends ScrollView, throws to my face a ClassCastException? is there any way to detect end of scrolling without messing too much?

Thank you people.

EDIT: As promised, here is the piece of my XML that matters:

<ScrollView
        android:id="@+id/scrollView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >


        <WebView
            android:id="@+id/textterms"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:gravity="center_horizontal"
            android:textColor="@android:color/black" />

    </ScrollView>

I changed it from TextView to WebView to be able of justifying the text inside. What i want to achieve is the "Accept button doesn't activate until the terms of the contract are fully read" thing. My extended class is called ScrollViewExt. If i change the tag ScrollView for ScrollViewExt it throws an

android.view.InflateException: Binary XML file line #44: Error inflating class ScrollViewExt

because it doesn't understand the tag ScrollViewEx. I don't think it has a solution...

Thanks for your answers!

No need for custom classes or complex extensions. Just use [`canScrollVertically(int)`](https://developer.android.com/reference/android/view/View.html#canScrollVertically(int)) — yuval, Feb 08 '18 at 20:00

score 114 · Accepted Answer · edited Feb 16 '14 at 06:01

114

Did it!

Aside of the fix Alexandre kindly provide me, I had to create an Interface:

public interface ScrollViewListener {
    void onScrollChanged(ScrollViewExt scrollView, 
                         int x, int y, int oldx, int oldy);
}

Then, i had to override the OnScrollChanged method from ScrollView in my ScrollViewExt:

public class ScrollViewExt extends ScrollView {
    private ScrollViewListener scrollViewListener = null;
    public ScrollViewExt(Context context) {
        super(context);
    }

    public ScrollViewExt(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

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

    public void setScrollViewListener(ScrollViewListener scrollViewListener) {
        this.scrollViewListener = scrollViewListener;
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);
        if (scrollViewListener != null) {
            scrollViewListener.onScrollChanged(this, l, t, oldl, oldt);
        }
    }
}

Now, as Alexandre said, put the package name in the XML tag (my fault), make my Activity class implement the interface created before, and then, put it all together:

scroll = (ScrollViewExt) findViewById(R.id.scrollView1);
scroll.setScrollViewListener(this);

And in the method OnScrollChanged, from the interface...

@Override
public void onScrollChanged(ScrollViewExt scrollView, int x, int y, int oldx, int oldy) {
    // We take the last son in the scrollview
    View view = (View) scrollView.getChildAt(scrollView.getChildCount() - 1);
    int diff = (view.getBottom() - (scrollView.getHeight() + scrollView.getScrollY()));

    // if diff is zero, then the bottom has been reached
    if (diff == 0) {
        // do stuff
    }
}

And it worked!

Thank you very much for your help, Alexandre!

edited Feb 16 '14 at 06:01

Parag Chauhan

35,760
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answered Apr 26 '12 at 13:23

Fustigador

6,339
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I am trying to use this answer in my application, and the problem is -scrollView.getHeight() is always equal to view.getBottom(), while scrollView.getScrollY() is always 0. Do you have any idea why that might be? – Marko Cakic Nov 29 '12 at 20:55
Thanks, that is brilliant as it allows creating arrows on the top and the bottom of the ScrollView and make them appear or disappear depending on the scrollview's position, to make the user aware that there are more items to see... – Lumis Jan 28 '13 at 18:38
@MarkoCakic See this answer to get the height of a scroll view's contents. http://stackoverflow.com/questions/3609297/android-total-height-of-scrollview – Uselessinfo Dec 12 '13 at 21:30
Since `scrollView` has only one child `view = scrollView.getChildAt(0)` and `scrollView.getScrollY()==y ` in your function, could the function be modified above using this,rather than accessing redundant data. – laaptu May 07 '15 at 06:15
I have one question, I am updating my scrollview dynamically so I dont want this on scrollChanged, I want to detect if the user scrolled up (turn autoscroll off) if the user scrolls down to the bottom (turn autoscroll on).. Cna anyone help please. – AL̲̳I Jul 03 '15 at 10:09
Check out this Ali http://stackoverflow.com/questions/4414929/android-scrollview-how-to-detect-begin-and-end-of-scrollview?rq=1 – Fustigador Jul 03 '15 at 10:33
@Fustigator, where to place the interface declaration of ScrollViewListener? – Brabbeldas Sep 03 '15 at 09:00
You mean this?: scroll = (ScrollViewExt) findViewById(R.id.scrollView1); scroll.setScrollViewListener(this); Its been a while since then, and if I remember correctly, its in the activity that has the scrollview you want to know when gets the bottom. – Fustigador Sep 03 '15 at 09:46
Your View-cast is obsolete :) – Bart Burg Nov 16 '15 at 11:50
@Fustigador: I created a interface seperate file and I have scrollview inside Fragment how do I call the: scrollview.setScrollViewListener(this); I tried scrollview.setScrollViewListener(getactivity()); this didn't work.. :( Can you please explain on what should come up? – TheDevMan Dec 07 '15 at 12:18
Its "this" because the activity or fragment where your scrollview is has to implement the interface you created, and "this" refers to itself. Depending of your situation, "this" could refer to other thing. If that is your case, try with nameofyourclass.ScrollViewListener instead of "this" – Fustigador Dec 07 '15 at 16:24
It seems to work for most of the cases (that is, scrollview consuming parent height), but doesn't seem to work when some other view exists below the scrollview – Narendra Singh Apr 04 '16 at 15:24
In my experience, you should check for if(diff <= 0) – MohanRaj S Nov 03 '16 at 11:10

Phong Nguyen · Answer 2 · 2018-08-16T09:58:00.987

103

I found a simple way to detect this :

   scrollView.getViewTreeObserver()
       .addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
            @Override
            public void onScrollChanged() {
                if (scrollView.getChildAt(0).getBottom()
                     <= (scrollView.getHeight() + scrollView.getScrollY())) {
                    //scroll view is at bottom
                } else {
                    //scroll view is not at bottom
                }
            }
        });

Doesn't need to custom ScrollView.
Scrollview can host only one direct child, so scrollView.getChildAt(0) is okay.
This solution is right even the height of direct child of scroll view is match_parent or wrap_content.

edited Aug 16 '18 at 09:58

answered Dec 14 '16 at 10:00

Phong Nguyen

6,897
2
26
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14

To avoid calling bottom multiple times replace "<=" with "==" – Harshil Pansare Jun 19 '17 at 12:02
1

THANK YOU, we shouldn't have to extend ScrollView to do something this common. – Andrew Koster Aug 17 '18 at 23:20
When the child uses margins, this doesn't work. A workaround is `scrollview(framelayout(childWithMargin)))` – m.reiter May 19 '21 at 11:06
1

definitely should have been the accepted answer – frogstair Jul 04 '21 at 11:37
this approach is not working when scrollview is present inside recyclerview. – Aayush Singh Apr 06 '22 at 06:15
it is worked even for recyclerview inside nested scroll view! tnx – NimaAzhd Dec 14 '22 at 16:17

yuval · Answer 3 · 2023-07-19T00:31:58.867

88

There is a simple built-in method that accomplishes this: canScrollVertically(int)

For example:

@Override
public void onScrollChanged() {
    if (!scrollView.canScrollVertically(1)) {
        // bottom of scroll view
    }
    if (!scrollView.canScrollVertically(-1)) {
        // top of scroll view
    }
}

This also works with RecyclerView, ListView, and actually any other view since the method is implemented on View.

If you have a horizontal ScrollView, the same can be achieved with canScrollHorizontally(int)

edited Jul 19 '23 at 00:31

answered Feb 08 '18 at 19:58

yuval

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3

For completeness, that's `!scrollView.canScrollHorizontally(1)` to check if it's already at the right end, and `!scrollView.canScrollHorizontally(-1)` if it's at the left. – keithmaxx May 13 '19 at 07:56

score 20 · Answer 4 · answered Sep 17 '15 at 04:08

Fustigador answer was great, but I found some device (Like Samsung Galaxy Note V) cannot reach 0, have 2 point left, after the calculation. I suggest to add a little buffer like below:

@Override
public void onScrollChanged(ScrollViewExt scrollView, int x, int y, int oldx, int oldy) {
    // We take the last son in the scrollview
    View view = (View) scrollView.getChildAt(scrollView.getChildCount() - 1);
    int diff = (view.getBottom() - (scrollView.getHeight() + scrollView.getScrollY()));

    // if diff is zero, then the bottom has been reached
    if (diff <= 10) {
        // do stuff
    }
}

score 16 · Answer 5 · answered Oct 12 '18 at 08:25

scrollView = (ScrollView) findViewById(R.id.scrollView);

    scrollView.getViewTreeObserver()
            .addOnScrollChangedListener(new 
            ViewTreeObserver.OnScrollChangedListener() {
                @Override
                public void onScrollChanged() {

                    if (!scrollView.canScrollVertically(1)) {
                        // bottom of scroll view
                    }
                    if (!scrollView.canScrollVertically(-1)) {
                        // top of scroll view


                    }
                }
            });

score 10 · Answer 6 · edited Feb 17 '13 at 06:16

EDIT

With the content of your XML, I can see that you use a ScrollView. If you want to use your custom view, you must write com.your.packagename.ScrollViewExt and you will be able to use it in your code.

<com.your.packagename.ScrollViewExt
    android:id="@+id/scrollView1"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <WebView
        android:id="@+id/textterms"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center_horizontal"
        android:textColor="@android:color/black" />

</com.your.packagename.ScrollViewExt>

EDIT END

Could you post the xml content ?

I think that you could simply add a scroll listener and check if the last item showed is the lastest one from the listview like :

mListView.setOnScrollListener(new OnScrollListener() {      
    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        // TODO Auto-generated method stub      
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        // TODO Auto-generated method stub
        if(view.getLastVisiblePosition()==(totalItemCount-1)){
            //dosomething
        }
    }
});

I will do it tomorrow, im not at work by now. But i see you are suggesting a ListView. Im not using a ListView, just a TextView inside a ScrollView. — Fustigador, Apr 25 '12 at 17:18
Oh sorry I was think of ListView. Could you post the xm called by setContentViewl with your custom view ? — Alexandre B., Apr 25 '12 at 20:50

score 7 · Answer 7 · answered Jul 07 '20 at 04:53

I went through the solutions on the internet. Mostly solutions didn't work in the project I'm working on. Following solutions work fine for me.

Using onScrollChangeListener (works on API 23):

   if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
        scrollView.setOnScrollChangeListener(new View.OnScrollChangeListener() {
            @Override
            public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {

                int bottom =   (scrollView.getChildAt(scrollView.getChildCount() - 1)).getHeight()-scrollView.getHeight()-scrollY;

                if(scrollY==0){
                    //top detected
                }
                if(bottom==0){
                    //bottom detected
                }
            }
        });
    }

using scrollChangeListener on TreeObserver

 scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
        @Override
        public void onScrollChanged() {
            int bottom =   (scrollView.getChildAt(scrollView.getChildCount() - 1)).getHeight()-scrollView.getHeight()-scrollView.getScrollY();

            if(scrollView.getScrollY()==0){
                //top detected
            }
            if(bottom==0) {
                //bottom detected
            }
        }
    });

Hope this solution helps :)

TheIT · Answer 8 · 2016-10-16T20:21:20.487

You can make use of the Support Library's NestedScrollView and it's NestedScrollView.OnScrollChangeListener interface.

https://developer.android.com/reference/android/support/v4/widget/NestedScrollView.html

Alternatively if your app is targeting API 23 or above, you can make use of the following method on the ScrollView:

View.setOnScrollChangeListener(OnScrollChangeListener listener)

Then follow the example that @Fustigador described in his answer. Note however that as @Will described, you should consider adding a small buffer in case the user or system isn't able to reach the complete bottom of the list for any reason.

Also worth noting is that the scroll change listener will sometimes be called with negative values or values greater than the view height. Presumably these values represent the 'momentum' of the scroll action. However unless handled appropriately (floor / abs) they can cause problems detecting the scroll direction when the view is scrolled to the top or bottom of the range.

https://developer.android.com/reference/android/view/View.html#setOnScrollChangeListener(android.view.View.OnScrollChangeListener)

Pranav · Answer 9 · 2016-12-22T05:58:40.963

We should always add scrollView.getPaddingBottom() to match full scrollview height because some time scroll view has padding in xml file so that case its not going to work.

scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
        @Override
        public void onScrollChanged() {
            if (scrollView != null) {
               View view = scrollView.getChildAt(scrollView.getChildCount()-1);
               int diff = (view.getBottom()+scrollView.getPaddingBottom()-(scrollView.getHeight()+scrollView.getScrollY()));

          // if diff is zero, then the bottom has been reached
               if (diff == 0) {
               // do stuff
                }
            }
        }
    });

score 2 · Answer 10 · edited Nov 21 '17 at 08:24

To determine if you are at the end of your custom ScrollView you could also use a member variable and store the last y-position. Then you can compare the last y-position with the current scroll position.

private int scrollViewPos;

...

@Override
public void onScrollChanged(ScrollViewExt scrollView, int x, int y, int oldx, int oldy) {

   //reached end of scrollview
   if (y > 0 && scrollViewPos == y){
      //do something
   }

   scrollViewPos = y;
}

Phate P · Answer 11 · 2018-07-23T22:12:23.760

Most of answers works beside a fact, that when u scroll to the bottom, listener is triggered several times, which in my case is undesirable. To avoid this behavior I've added flag scrollPositionChanged that checks if scroll position even changed before calling method once again.

public class EndDetectingScrollView extends ScrollView {
    private boolean scrollPositionChanged = true;

    private ScrollEndingListener scrollEndingListener;

    public interface ScrollEndingListener {
        void onScrolledToEnd();
    }

    @Override
    protected void onScrollChanged(int l, int t, int oldl, int oldt) {
        super.onScrollChanged(l, t, oldl, oldt);

        View view = this.getChildAt(this.getChildCount() - 1);
        int diff = (view.getBottom() - (this.getHeight() + this.getScrollY()));
        if (diff <= 0) {
            if (scrollPositionChanged) {
                scrollPositionChanged = false;
                if (scrollEndingListener != null) {
                    scrollEndingListener.onScrolledToEnd();
                }
            }
        } else {
            scrollPositionChanged = true;
        }
    }

    public void setScrollEndingListener(ScrollEndingListener scrollEndingListener) {
        this.scrollEndingListener = scrollEndingListener;
    }
}

Then just set listener

scrollView.setScrollEndingListener(new EndDetectingScrollView.ScrollEndingListener() {
    @Override
    public void onScrolledToEnd() {
        //do your stuff here    
    }
});

You may do the same thing if u do in like

scrollView.getViewTreeObserver().addOnScrollChangedListener(...)

but you have to provide flag from class your adding this listener.

Nice! Works well for pre API level 23 ! – Abhiroop Nandi Ray Jun 11 '18 at 16:35 — Abhiroop Nandi Ray, Jun 11 '18 at 16:35

G00fY · Answer 12 · 2019-09-05T21:32:05.257

0

I wanted to show/hide a FAB with an offset before the very bottom of the scrollview. This is the solution I came up with (Kotlin):

scrollview.viewTreeObserver.addOnScrollChangedListener {
    if (scrollview.scrollY < scrollview.getChildAt(0).bottom - scrollview.height - offset) {
        // fab.hide()
    } else {
        // fab.show()
    }
}

edited Sep 05 '19 at 21:32

answered Jul 03 '19 at 13:50

G00fY

4,545
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score 0 · Answer 13 · answered Sep 08 '21 at 12:07

The answer is very simple:

Just add a OnScrollChangedListener to your scrollView (RecyclerView or NestedScrollBar, etc) and implement the onScrollChanged method. For instance, if you use a NestedScrollView:

val nestedScrollView = view.findViewById<NestedScrollView>(R.id.nested_scroll_view_id)
nestedScrollView.viewTreeObserver?.addOnScrollChangedListener {
    if (!nestedScrollView.canScrollVertically(1)) {
        button.isEnabled = true
    }
}

Let me now if you have any problem with this.

Detect end of ScrollView

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