Android : Handling child recyclerview vertical scroll and click in parent recyclerview header

Question

I need to implement a recyclerview with fixed height (250 dp) which scrolls vertically in the header of parent recyclerview which also scrolls vertically. And also header has a button in it. I am not able to get the child recyclerview's click or scroll . How we can achieve both parent recyclerview scroll and child recyclerview scroll(which is in header of parent)?

Answer 1

In fact, it will be easier to answer if you add the code you applied while asking the question. Other than that, you can use a dotindicator for the recyclerview. This recyclerview will scroll automatically as it scrolls.

Example :

 final int radius = getResources().getDimensionPixelSize(R.dimen.radius);
        final int dotsHeight = getResources().getDimensionPixelSize(R.dimen.dotsHeight);
        final int color = ContextCompat.getColor(getApplicationContext(), R.color.appcolor1);
        recyclerViewSlider.addItemDecoration(new DotsIndicatorDecoration(radius, radius * 4, dotsHeight, color, color));

DotsIndicatorDecoration.java

import android.content.res.Resources;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.util.Log;
import android.view.View;

import androidx.annotation.ColorInt;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import org.jetbrains.annotations.NotNull;

public class DotsIndicatorDecoration extends RecyclerView.ItemDecoration {

    private final int indicatorHeight;
    private final int indicatorItemPadding;
    private final int radius;

    private final Paint inactivePaint = new Paint();
    private final Paint activePaint = new Paint();

    public DotsIndicatorDecoration(int radius, int padding, int indicatorHeight, @ColorInt int colorInactive, @ColorInt int colorActive) {
        float strokeWidth = Resources.getSystem().getDisplayMetrics().density * 1;
        this.radius = radius;
        inactivePaint.setStrokeCap(Paint.Cap.ROUND);
        inactivePaint.setStrokeWidth(strokeWidth);
        inactivePaint.setStyle(Paint.Style.STROKE);
        inactivePaint.setAntiAlias(true);
        inactivePaint.setColor(colorInactive);

        activePaint.setStrokeCap(Paint.Cap.ROUND);
        activePaint.setStrokeWidth(strokeWidth);
        activePaint.setStyle(Paint.Style.FILL);
        activePaint.setAntiAlias(true);
        activePaint.setColor(colorActive);

        this.indicatorItemPadding = padding;
        this.indicatorHeight = indicatorHeight;
    }

    @Override
    public void onDrawOver(@NotNull Canvas c, @NotNull RecyclerView parent, @NotNull RecyclerView.State state) {
        super.onDrawOver(c, parent, state);

        final RecyclerView.Adapter adapter = parent.getAdapter();

        if (adapter == null) {
            return;
        }

        int itemCount = adapter.getItemCount();

        // center horizontally, calculate width and subtract half from center
        float totalLength = this.radius * 2 * itemCount;
        float paddingBetweenItems = Math.max(0, itemCount - 1) * indicatorItemPadding;
        float indicatorTotalWidth = totalLength + paddingBetweenItems;
        float indicatorStartX = (parent.getWidth() - indicatorTotalWidth) / 2f;

        // center vertically in the allotted space
        Log.d("olley", parent.getHeight() + "--" + indicatorHeight);
        float indicatorPosY = parent.getHeight()*0.9f - indicatorHeight/2f;

        drawInactiveDots(c, indicatorStartX, indicatorPosY, itemCount);

        final int activePosition;

        if (parent.getLayoutManager() instanceof GridLayoutManager) {
            activePosition = ((GridLayoutManager) parent.getLayoutManager()).findFirstVisibleItemPosition();
        } else if (parent.getLayoutManager() instanceof LinearLayoutManager) {
            activePosition = ((LinearLayoutManager) parent.getLayoutManager()).findFirstVisibleItemPosition();
        } else {
            // not supported layout manager
            return;
        }

        if (activePosition == RecyclerView.NO_POSITION) {
            return;
        }

        // find offset of active page if the user is scrolling
        final View activeChild = parent.getLayoutManager().findViewByPosition(activePosition);
        if (activeChild == null) {
            return;
        }

        drawActiveDot(c, indicatorStartX, indicatorPosY, activePosition);
    }

    private void drawInactiveDots(Canvas c, float indicatorStartX, float indicatorPosY, int itemCount) {
        // width of item indicator including padding
        final float itemWidth = this.radius * 2 + indicatorItemPadding;

        float start = indicatorStartX + radius;
        for (int i = 0; i < itemCount; i++) {
            c.drawCircle(start, indicatorPosY, radius, inactivePaint);
            start += itemWidth;
        }
    }

    private void drawActiveDot(Canvas c, float indicatorStartX, float indicatorPosY,
                               int highlightPosition) {
        // width of item indicator including padding
        final float itemWidth = this.radius * 2 + indicatorItemPadding;
        float highlightStart = indicatorStartX + radius + itemWidth * highlightPosition;
        c.drawCircle(highlightStart, indicatorPosY, radius, activePaint);
    }

    @Override
    public void getItemOffsets(@NotNull Rect outRect, @NotNull View view, @NotNull RecyclerView parent, @NotNull RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);
        outRect.bottom = indicatorHeight; //evil just like cat on box
    }
}

I hope you want something like this. You can make adjustments etc. in the :) redirect.