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  lt ScrollView gt  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    lt ScrollView         android id    id scrollView1          android layout width  match parent          android layout height  match parent   gt             lt WebView             android id    id textterms              android layout width  match parent              android layout height  match parent              android gravity  center horizontal              android textColor   android color black    gt        lt  ScrollView gt    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

User · Answer

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  lt   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

User · Answer

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

User · Answer

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  lt   10               do stuff

User · Answer

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  lt  scrollview getChildAt 0  bottom - scrollview height - offset               fab hide         else              fab show

User · Answer

I found a simple way to detect this       scrollView getViewTreeObserver           addOnScrollChangedListener new ViewTreeObserver OnScrollChangedListener                  Override             public void onScrollChanged                     if  scrollView getChildAt 0  getBottom                         lt    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

User · Answer

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  gt   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

User · Answer

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

User · Answer

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

User · Answer

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  gt  0  amp  amp  scrollViewPos    y           do something          scrollViewPos   y

User · Answer

All of these answers are so complicated  but 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

User · Answer

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    lt com your packagename ScrollViewExt     android id    id scrollView1      android layout width  match parent      android layout height  match parent   gt        lt WebView         android id    id textterms          android layout width  match parent          android layout height  match parent          android gravity  center horizontal          android textColor   android color black    gt    lt  com your packagename ScrollViewExt gt    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

User · Answer

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

[android] Detect end of ScrollView

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Examples related to android-scrollview