OnScrollChangeListener for ScrollView - android-studio

Question

I would like to make a function to intercept a certain scroll at the top of the view.
to do this I'm trying to use OnScrollChangeListener.
My view contains a ScrollView
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="#+id/scrollViewClientPhysique"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#color/fond"
tools:context=".client.FicheClient">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical">**strong text**
and I initialize addOnScrollChangedListener in a function I call inside onCreateView
fun initializeInfiniteScroll(){
val scrollView = myView.findViewById<View>(R.id.scrollViewClientPhysique) as ScrollView
scrollView.viewTreeObserver.addOnScrollChangedListener {
if (scrollView != null) {
val view = scrollView.getChildAt(scrollView.childCount - 1)
val diff =
view.bottom + scrollView.paddingBottom - (scrollView.height + scrollView.scrollY)
if (diff == 0) {
// do stuff
}
}
}
}
but when when I scroll the view I don't enter addOnScrollChangedListener to intercept how many dp the scroll is.
what am I doing wrong?

Answer 1

Please update your ScrollChangedListener as mentioned below.
public class MainActivity extends AppCompatActivity implements View.OnTouchListener,
ViewTreeObserver.OnScrollChangedListener {
ScrollView scrollView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
scrollView = findViewById(R.id.scrollView);
scrollView.setOnTouchListener(this);
scrollView.getViewTreeObserver().addOnScrollChangedListener(this);
}
public void onScrollChanged(){
View view = scrollView.getChildAt(scrollView.getChildCount() - 1);
int topDetector = scrollView.getScrollY();
int bottomDetector = view.getBottom() - (scrollView.getHeight() + scrollView.getScrollY());
//TODO: Just added for testing/understanding. Please add/replace your own logic..
if(bottomDetector == 0 ){
Toast.makeText(this,"Scroll View bottom reached",Toast.LENGTH_SHORT).show();
}
if(topDetector <= 0){
Toast.makeText(this,"Scroll View top reached",Toast.LENGTH_SHORT).show();
}
}
#Override
public boolean onTouch(View v, MotionEvent event) {
return false;
}
}