问题
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!
回答1:
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();
}
回答2:
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>
回答3:
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;
}
}
回答4:
You can try this:
nestedScrollView.fling(0);
nestedScrollView.smoothScrollTo(0, 0);
来源：https://stackoverflow.com/questions/52083678/nestedscrollviews-smoothscrollto-behaves-weird