启用子ScrollView时禁用父ScrollView

Question

I have two ScrollViews in my layout like so

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

    <!-- Extra Content -->

    <android.support.v7.widget.CardView
        android:id="@+id/news_comment_card"
        android:layout_width="match_parent"
        android:layout_height="180dp"
        app:cardCornerRadius="8sp"
        app:cardElevation="@dimen/elevation_card">

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

            <TextView
                android:id="@+id/news_comment_header"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text="Comments"
                android:textColor="@color/colorAccent"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

            <android.support.v7.widget.RecyclerView
                android:id="@+id/news_comment_section"
                android:layout_width="0dp"
                android:layout_height="0dp"
                app:layout_constraintBottom_toTopOf="@+id/news_comment_expand"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/news_comment_header"/>

            <Button
                android:id="@+id/news_comment_expand"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:text="@string/show_all_comments"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintLeft_toLeftOf="parent"
                app:layout_constraintRight_toRightOf="parent"/>

        </android.support.constraint.ConstraintLayout>  
</ScrollView>

I initially disable news_comment_section using the following code in my Activity commentSection.setOnTouchListener(new IgnoreTouch()); .

IgnoreTouch is a helper class that ignores touch events like so

 private class IgnoreTouch implements View.OnTouchListener{
    @Override
    public boolean onTouch(View v, MotionEvent event) {
        return true;
    }
}

This works in disabling the scrolling for commentsList . When the Button news_comment_expand is clicked the CardView news_comment_card expands it's height to fill the screen and I call the following

newsPageScroller.setOnTouchListener(new IgnoreTouch());
newsPageScroller.requestDisallowInterceptTouchEvent(true);
commentSection.setOnTouchListener(null);

This disables news_page_scroller and enables news_comment_section . This works up until I reach the top or bottom of news_comment_section . If I continue to scroll news_comment_section after I reach the top or bottom of the list, the parent ScrollView, news_page_scroller , starts scrolling. How do I completely disable any scrolling from happening on the parent ScrollView news_page_scroller ?

Answer 1

I was able to solve this by creating a class that extends ScrollView

public class PausableScrollView extends ScrollView {
    private boolean scrollEnabled = true;
    public void setScrollEnabled(boolean scrollEnabled){
        this.scrollEnabled = scrollEnabled;
    }

    public PausableScrollView(Context context) { super(context); }

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

    public PausableScrollView(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); }

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

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
        if(scrollEnabled) {
            super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
        }
    }
}

Basically, I can call newsPageScroller.setScrollEnabled(false) to ignore all scrolling events taking place on the newsPageScroller .

Answer 2

This will disable scrolling the parent from a child during fling and scroll without having to manually enable and disable:

class ContainerScrollView @JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyleAttr: Int = 0) 
    : ScrollView(context, attrs, defStyleAttr) {

    private var isScrollingChild = false

    override fun onScrollChanged(l: Int, t: Int, oldl: Int, oldt: Int) {
        if (!isScrollingChild) {
            super.onScrollChanged(l, t, oldl, oldt)
        }
    }

    override fun onNestedScroll(target: View?, dxConsumed: Int, dyConsumed: Int, dxUnconsumed: Int, dyUnconsumed: Int) {
        if (!isScrollingChild) {
            super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed)
        }
    }

    override fun onStartNestedScroll(child: View?, target: View?, nestedScrollAxes: Int): Boolean {
        isScrollingChild = true
        return super.onStartNestedScroll(child, target, nestedScrollAxes)
    }

    override fun onStopNestedScroll(target: View?) {
        isScrollingChild = false
        super.onStopNestedScroll(target)
    }
}