CoordinatorLayout inside another CoordinatorLayout

Question

CorodinatorLayout inside another CoordinatorLayout such that scrolling the child-view should also scroll the Parent CoordinatorLayout.

Answer 1

Hopefully, this will help others. The idea I implemented during preScroll calculates how much the parent is able to consume, if it is already 0, then call super.onNestedPreScroll.

Here's the code:

import android.content.Context;
import android.support.annotation.Nullable;
import android.support.design.widget.CoordinatorLayout;
import android.support.v4.view.NestedScrollingChild2;
import android.support.v4.view.NestedScrollingChildHelper;
import android.util.AttributeSet;
import android.view.View;

public class NestedScrollCoordinatorLayout extends CoordinatorLayout implements NestedScrollingChild2 {

  private NestedScrollingChildHelper mChildHelper;

  public NestedScrollCoordinatorLayout(Context context) {
    super(context);
    mChildHelper = new NestedScrollingChildHelper(this);
    setNestedScrollingEnabled(true);
  }

  public NestedScrollCoordinatorLayout(Context context, AttributeSet attrs) {
    super(context, attrs);
    mChildHelper = new NestedScrollingChildHelper(this);
    setNestedScrollingEnabled(true);
  }

  public NestedScrollCoordinatorLayout(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    mChildHelper = new NestedScrollingChildHelper(this);
    setNestedScrollingEnabled(true);
  }

  @Override
  public boolean isNestedScrollingEnabled() {
    return mChildHelper.isNestedScrollingEnabled();
  }

  @Override
  public void setNestedScrollingEnabled(boolean enabled) {
    mChildHelper.setNestedScrollingEnabled(enabled);
  }

  @Override
  public boolean hasNestedScrollingParent() {
    return mChildHelper.hasNestedScrollingParent();
  }

  @Override
  public boolean hasNestedScrollingParent(int type) {
    return mChildHelper.hasNestedScrollingParent(type);
  }

  @Override
  public boolean onStartNestedScroll(View child, View target, int axes, int type) {
    boolean superResult = super.onStartNestedScroll(child, target, axes, type);
    return startNestedScroll(axes, type) || superResult;
  }

  @Override
  public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
    boolean superResult = super.onStartNestedScroll(child, target, nestedScrollAxes);
    return startNestedScroll(nestedScrollAxes) || superResult;
  }

  @Override
  public void onNestedPreScroll(View target, int dx, int dy, int[] consumed, int type) {
    dispatchNestedPreScroll(dx, dy, consumed, null);
    if (consumed[1] == 0) {
      super.onNestedPreScroll(target, dx, dy, consumed, type);
    }
  }

  @Override
  public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
    dispatchNestedPreScroll(dx, dy, consumed, null);
    if (consumed[1] == 0) {
      super.onNestedPreScroll(target, dx, dy, consumed);
    }
  }

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

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

  @Override
  public void onStopNestedScroll(View target, int type) {
    super.onStopNestedScroll(target, type);
    stopNestedScroll(type);
  }

  @Override
  public void onStopNestedScroll(View target) {
    super.onStopNestedScroll(target);
    stopNestedScroll();
  }

  @Override
  public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
    boolean superResult = super.onNestedPreFling(target, velocityX, velocityY);
    return dispatchNestedPreFling(velocityX, velocityY) || superResult;
  }

  @Override
  public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
    boolean superResult = super.onNestedFling(target, velocityX, velocityY, consumed);
    return dispatchNestedFling(velocityX, velocityY, consumed) || superResult;
  }

  @Override
  public boolean startNestedScroll(int axes, int type) {
    return mChildHelper.startNestedScroll(axes, type);
  }

  @Override
  public boolean startNestedScroll(int axes) {
    return mChildHelper.startNestedScroll(axes);
  }

  @Override
  public void stopNestedScroll() {
    mChildHelper.stopNestedScroll();
  }

  @Override
  public void stopNestedScroll(int type) {
    mChildHelper.stopNestedScroll(type);
  }

  @Override
  public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, @Nullable int[] offsetInWindow, int type) {
    return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow, type);
  }

  @Override
  public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, @Nullable int[] offsetInWindow) {
    return mChildHelper.dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, offsetInWindow);
  }

  @Override
  public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed, @Nullable int[] offsetInWindow) {
    return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow);
  }

  @Override
  public boolean dispatchNestedPreScroll(int dx, int dy, @Nullable int[] consumed, @Nullable int[] offsetInWindow, int type) {
    return mChildHelper.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type);
  }

  @Override
  public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
    return mChildHelper.dispatchNestedPreFling(velocityX, velocityY);
  }

  @Override
  public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
    return mChildHelper.dispatchNestedFling(velocityX, velocityY, consumed);
  }
}

See also this gist on GithHub