Android: Collapsing Linearlayout instead of Collapsing Toolbar

Question

I\'m trying to create a Master/Detail transaction in a single fragment. I thought of using LinearLayout as the container of my edittext for my header. Then a RecyclerView fo

Answer 1

Based on RIP's tutorial, you can collapse or expand views using the snippet below.

public class ViewAnimationUtils {
        
        public static void expand(final View v) {
            v.measure(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT);
            final int targtetHeight = v.getMeasuredHeight();
    
            v.getLayoutParams().height = 0;
            v.setVisibility(View.VISIBLE);
            Animation a = new Animation()
            {
                @Override
                protected void applyTransformation(float interpolatedTime, Transformation t) {
                    v.getLayoutParams().height = interpolatedTime == 1
                            ? LayoutParams.WRAP_CONTENT
                            : (int)(targtetHeight * interpolatedTime);
                    v.requestLayout();
                }
    
                @Override
                public boolean willChangeBounds() {
                    return true;
                }
            };
    
            a.setDuration((int)(targtetHeight / v.getContext().getResources().getDisplayMetrics().density));
            v.startAnimation(a);
        }
    
        public static void collapse(final View v) {
            final int initialHeight = v.getMeasuredHeight();
    
            Animation a = new Animation()
            {
                @Override
                protected void applyTransformation(float interpolatedTime, Transformation t) {
                    if(interpolatedTime == 1){
                        v.setVisibility(View.GONE);
                    }else{
                        v.getLayoutParams().height = initialHeight - (int)(initialHeight * interpolatedTime);
                        v.requestLayout();
                    }
                }
    
                @Override
                public boolean willChangeBounds() {
                    return true;
                }
            };
    
            a.setDuration((int)(initialHeight / v.getContext().getResources().getDisplayMetrics().density));
            v.startAnimation(a);
        }
    }

In addition, to specify the logic being applied to the animated view, in your case, it could be used a ScrollListener like

private fun RecyclerView.onViewScroll(title: String): OnScrollListener {
    return object : OnScrollListener() {
        override fun onScrollStateChanged(recyclerView: RecyclerView, state: Int) {
            super.onScrollStateChanged(recyclerView, state)
            rootView.findViewById(R.id.views_menu_header).let { layout ->
                if(state == SCROLL_STATE_DRAGGING) {                     
                    collapse(layout)
                }
            }
        }
    }
}

then attaching the listener to your recycler

findViewById(R.id.views_menu_items).apply { addOnScrollListener(onViewScroll(title)) }

which would collapse R.id.views_menu_header whenever the R.id.views_menu_items starts being dragged.