NestedScrollView's smoothScrollTo() behaves weird

Question

What I am trying to achieve is to scroll to scroll_position_1 when tab1 (and so on) is clicked like this. I don't understand what's happening at all. Below is the structure of my layout.

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v4.widget.NestedScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.constraint.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <TextView
                android:id="@+id/scroll_position_1"
                android:layout_width="0dp"
                android:layout_height="wrap_content" />

            <TextView
                android:id="@+id/scroll_position_2"
                android:layout_width="0dp"
                android:layout_height="wrap_content" />

        </android.support.constraint.ConstraintLayout>
    </android.support.v4.widget.NestedScrollView>

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

        <android.support.design.widget.CollapsingToolbarLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            app:layout_scrollFlags="scroll|snap">

            <ImageView
                android:layout_width="match_parent"
                android:layout_height="180dp"
                android:scaleType="centerCrop"
                app:layout_collapseMode="parallax"/>

            <android.support.v7.widget.Toolbar
                android:layout_width="match_parent"
                android:layout_height="?attr/actionBarSize"
                app:layout_collapseMode="pin"
                app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>
        </android.support.design.widget.CollapsingToolbarLayout>
    </android.support.design.widget.AppBarLayout>

    <android.support.design.widget.TabLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <android.support.design.widget.TabItem
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"/>

        <android.support.design.widget.TabItem
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"/>
    </android.support.design.widget.TabLayout>
</android.support.design.widget.CoordinatorLayout>

This is how I scroll upon tab click but does not work:

mNestedScroller.smoothScrollTo(0, scroll_position_1_text_view.getY());

Whereas modifying it to:

mNestedScroller.scrollTo(0, scroll_position_1_text_view.getY());

works without problem! Please help. Thanks!

https://stackoverflow.com/questions/46156882/nestedscrollviews-fullscrollview-focus-up-not-working-properly/46171939#46171939 — AskNilesh, Sep 10 '18 at 12:37
yes, this is similar to what solved my problem. posting my solution. thanks. — user1506104, Sep 10 '18 at 16:38

user1506104 · Accepted Answer · 2018-10-22T03:59:20.143

8

Looks like there is a bug when programmatically scrolling NestedScrollView within CoordinatorLayout. This solved my problem:

private void scrollToView(final View view) {
    mScroller.scrollBy(0, 1);
    mScroller.smoothScrollTo(0, view.getTop());
}

or for better control:

private void scrollToView(final View view) {
    mScroller.scrollBy(0, 1);
    ObjectAnimator.ofInt(mScroller, "scrollY",  view.getTop()).setDuration(700).start();
}

edited Oct 22 '18 at 03:59

answered Sep 10 '18 at 16:36

user1506104

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Should we pass coordinator layout in view as a param? or parent view? – Hamza Khan Sep 16 '21 at 15:42

Venkata Narayana · Answer 2 · 2018-09-09T07:15:20.917

You can use a ListView instead of a ConstraintLayout and add the text views to the list. Then, you can simply call listView.smoothScrollToPosition(index) instead of worrying about the x and y coordinates.

1) Edit your layout as shown below.

2) Add items to your ListView via code.

3) Upon tab click, call listView.smoothScrollToPosition(index_of_text_view) and your list view scrolls to that position.

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout 
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.v4.widget.NestedScrollView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:layout_behavior="@string/appbar_scrolling_view_behavior">

      <LinearLayout
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:orientation="vertical"
       app:layout_behavior="@string/appbar_scrolling_view_behavior">

        <android.support.design.widget.TabLayout
        android:id="@+id/sliding_tabs"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"/>

          <android.support.design.widget.TabLayout
              android:layout_width="match_parent"
              android:layout_height="wrap_content">

              <android.support.design.widget.TabItem
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"/>

              <android.support.design.widget.TabItem
                  android:layout_height="wrap_content"
                  android:layout_width="wrap_content"/>
          </android.support.design.widget.TabLayout>

          <ListView
           android:id="@+id/list_view"
           android:layout_width="match_parent"
           android:layout_height="wrap_content"/>
       </LinearLayout
</android.support.v4.widget.NestedScrollView>

<android.support.design.widget.AppBarLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar">

    <android.support.design.widget.CollapsingToolbarLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_scrollFlags="scroll|snap">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="180dp"
            android:scaleType="centerCrop"
            app:layout_collapseMode="parallax"/>

        <android.support.v7.widget.Toolbar
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            app:layout_collapseMode="pin"
            app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>
    </android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>

Since your code already contains a NestedScrollView, just replace the Constraint Layot with a list view — Venkata Narayana, Sep 01 '18 at 16:43
yes. same issue. it seems like before doing the smooth scroll, i need to let the coordinator layout know about the scroll? — user1506104, Sep 09 '18 at 15:30
You were scrolling to the top of the item in your view like scroll_position_1_text_view.getY();. If that value is relative, you need to add the top of the container view as well like shown in the above link. Can you try that out? — Venkata Narayana, Sep 09 '18 at 16:13
[Thanks for your help.] view.getY() is relative to the scroller. I tried the value with mNestedScroller.scrollTo(), scrolls to the right spot. When used with mNestedScroller.smoothScrollTo(), it just scrolls down/weird. — user1506104, Sep 09 '18 at 16:18

Edijae Crusar · Answer 3 · 2018-09-10T08:13:53.433

When tab is clicked, just get the desired view's y position relative to the root view and scroll to that position.

public class MainActivity extends AppCompatActivity {

  private NestedScrollView nestedScrollView;
  private CoordinatorLayout coordinatorLayout;
  TextView textView;


  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    nestedScrollView = findViewById(R.id.nsv);
    coordinatorLayout = findViewById(R.id.cl);
    textView = findViewById(R.id.scroll_position_1);

    TabLayout tabLayout = findViewById(R.id.tl);
    tabLayout.addOnTabSelectedListener(new TabLayout.BaseOnTabSelectedListener() {
      @Override
      public void onTabSelected(TabLayout.Tab tab) {
        if(tab.getPosition() == 1/*position of your desired tab*/){
          scrollToView(textView);
        }
      }

      @Override
      public void onTabUnselected(TabLayout.Tab tab) {

      }

      @Override
      public void onTabReselected(TabLayout.Tab tab) {

      }
    });

  }

  /*
   * Used to scroll to the given view.
   *
   * @param view View to which we need to scroll.
   */
  private void scrollToView(View view) {
    // Get deepChild Offset
    int position = getRelativeTop(view);
    final int finalPosition = position;
    nestedScrollView.fling(0);
    nestedScrollView.smoothScrollTo(0, finalPosition);
  }

  private int getRelativeTop(View myView) {
    Rect offsetViewBounds = new Rect();
//returns the visible bounds
    myView.getDrawingRect(offsetViewBounds);
// calculates the relative coordinates to the parent
    coordinatorLayout.offsetDescendantRectToMyCoords(myView, offsetViewBounds);

    int relativeTop = offsetViewBounds.top;
    int relativeLeft = offsetViewBounds.left;
    return relativeTop;
  }

}

it did not work. giving you +1 anyways. by the way, why window focus? — user1506104, Sep 09 '18 at 04:13
@user1506104 `onWindowFocusChanged(boolean hasFocus)` is called when the current Window of the activity gains or loses focus. So i was just calling it explicitly but it works even without calling the method. I've tested it. see my edited answer. — Edijae Crusar, Sep 10 '18 at 08:15

score 1 · Answer 4 · edited Oct 18 '18 at 14:13

1

You can try this:

nestedScrollView.fling(0);
nestedScrollView.smoothScrollTo(0, 0);

edited Oct 18 '18 at 14:13

סטנלי גרונן

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answered Oct 18 '18 at 12:14

Swetha Reddy

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NestedScrollView's smoothScrollTo() behaves weird

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