CoordinatorLayout inside another CoordinatorLayout

Question

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

Answer 1

I have wrote one ChildCoordinatorLayout in my repo nestrefresh. In this repo, I wrap one AppBarLayout with ChildCoordinatorLayout and also add pull refresh for the ChildCoordinatorLayout with pull refresh behavior. And dyUnConsumed give parent firstly then to the child. This is the code:

class ChildCoordinatorLayout @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = 0
) : CoordinatorLayout(context, attrs, defStyleAttr), NestedScrollingChild2 {

    private lateinit var childHelper: NestedScrollingChildHelper

    init {
        init()
    }

    private fun init() {
        childHelper = NestedScrollingChildHelper(this)
        childHelper.isNestedScrollingEnabled = true
    }

    override fun setNestedScrollingEnabled(enabled: Boolean) {
        childHelper.isNestedScrollingEnabled = enabled
    }

    override fun isNestedScrollingEnabled(): Boolean {
        return childHelper.isNestedScrollingEnabled
    }

    override fun startNestedScroll(i: Int, i1: Int): Boolean {
        return childHelper.startNestedScroll(i, i1)
    }

    override fun stopNestedScroll(i: Int) {
        childHelper.stopNestedScroll(i)
    }

    override fun hasNestedScrollingParent(i: Int): Boolean {
        return childHelper.hasNestedScrollingParent()
    }

    override fun dispatchNestedScroll(i: Int, i1: Int, i2: Int, i3: Int, ints: IntArray?, i4: Int): Boolean {
        return childHelper.dispatchNestedScroll(i, i1, i2, i3, ints, i4)
    }

    override fun dispatchNestedPreScroll(i: Int, i1: Int, ints: IntArray?, ints1: IntArray?, i2: Int): Boolean {
        return childHelper.dispatchNestedPreScroll(i, i1, ints, ints1, i2)
    }

    override fun dispatchNestedPreFling(velocityX: Float, velocityY: Float): Boolean {
        return childHelper.dispatchNestedPreFling(velocityX, velocityY)
    }

    override fun dispatchNestedFling(velocityX: Float, velocityY: Float, consumed: Boolean): Boolean {
        return childHelper.dispatchNestedFling(velocityX, velocityY, consumed)
    }

    override fun onStartNestedScroll(child: View, target: View, axes: Int, type: Int): Boolean {
        if (type == TYPE_TOUCH) {
            stopNestedScroll(TYPE_NON_TOUCH)
            ViewCompat.stopNestedScroll(child, TYPE_NON_TOUCH)
        }
        val handle = super.onStartNestedScroll(child, target, axes, type)
        return startNestedScroll(axes, type) || handle
    }

    override fun onStopNestedScroll(target: View, type: Int) {
        super.onStopNestedScroll(target, type)
        stopNestedScroll(type)
    }

    override fun onNestedPreScroll(target: View, dx: Int, dy: Int, consumed: IntArray, type: Int) {
        val thisConsume = IntArray(2)
        dispatchNestedPreScroll(dx, dy, thisConsume, null, type)
        consumed[0] += thisConsume[0]
        consumed[1] += thisConsume[1]
        thisConsume[0] = 0
        thisConsume[1] = 0
        super.onNestedPreScroll(target, dx - consumed[0], dy - consumed[1], thisConsume, type)
        consumed[0] += thisConsume[0]
        consumed[1] += thisConsume[1]

    }

    override fun onNestedScroll(
        target: View,
        dxConsumed: Int,
        dyConsumed: Int,
        dxUnconsumed: Int,
        dyUnconsumed: Int,
        type: Int
    ) {

        val offsetInWindow = IntArray(2)
        target.getLocationInWindow(offsetInWindow)
        val startX = offsetInWindow[0]
        val startY = offsetInWindow[1]
        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed, type)
        target.getLocationInWindow(offsetInWindow)
        offsetInWindow[0] -= startX
        offsetInWindow[1] -= startY
        dispatchNestedScroll(dxConsumed, dyConsumed, dxUnconsumed + offsetInWindow[0]
            , dyUnconsumed + offsetInWindow[1], null, type)
    }

    override fun onNestedPreFling(target: View, velocityX: Float, velocityY: Float): Boolean {
        val handled = super.onNestedPreFling(target, velocityX, velocityY)
        return dispatchNestedPreFling(velocityX, velocityY) || handled
    }

    override fun onNestedFling(target: View, velocityX: Float, velocityY: Float, consumed: Boolean): Boolean {
        val handled = super.onNestedFling(target, velocityX, velocityY, consumed)
        return dispatchNestedFling(velocityX, velocityY, consumed) || handled
    }

}

Answer 2

Unfortunately, this is not supported by CoordinatorLayout.

Check the code in NestedScrollingChildHelper.startNestedScroll() and CoordinatorLayout.onStartNestedScroll(), the nested scrolling event is "consumed" if one of Behaviors of your inner CoordinatorLayout consumes it, and won't be further propagated.

Answer 3

I made this a library, see it on GitHub.

You just use <NestedScrollCoordinatorLayout> in your layout.

Answer 4

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

Answer 5

Here's a simple implementation of a nested coordinator layout.

/**
 * This variation of CoordinatorLayout also serves as a nested scrolling child,
 * which supports passing nested scrolling operations to it's parent when it's
 * own nested scrolling is locked.
 */
public class NestedCoordinatorLayout extends CoordinatorLayout implements NestedScrollingChild {

    private NestedScrollingChildHelper mChildHelper;
    private volatile boolean mPassToParent;

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

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

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

    /**
     * Locks the nested scrolling. Further scroll events will
     * be passed to the nested scrolling parent.
     */
    public void lockNestedScrolling() {
        mPassToParent = true;
    }

    /**
     * Unlocks the nested scrolling. Further scroll events will
     * be dispatched to this layout's own scrolling children.
     */
    public void unlockNestedScrolling() {
        mPassToParent = false;
    }

    /*
     * NestedScrollingParent implementation
     */

    @Override
    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
        /* Enable the scrolling behavior of our own children */
        super.onStartNestedScroll(child, target, nestedScrollAxes);
        /* Enable the scrolling behavior of the parent's other children  */
        startNestedScroll(nestedScrollAxes);
        /* Start tracking the current scroll */
        return true;
    }

    @Override
    public void onStopNestedScroll(View target) {
        /* Disable the scrolling behavior of our own children */
        super.onStopNestedScroll(target);
        /* Disable the scrolling behavior of the parent's other children  */
        stopNestedScroll();
    }

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

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

    @Override
    public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
        if (mPassToParent) {
            return dispatchNestedPreFling(velocityX, velocityY);
        } else {
            return super.onNestedPreFling(target, velocityX, velocityY);
        }
    }

    @Override
    public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
        if (mPassToParent) {
            return dispatchNestedFling(velocityX, velocityY, consumed);
        } else {
            return super.onNestedFling(target, velocityX, velocityY, consumed);
        }
    }

    /*
     * NestedScrollingChild implementation
     */

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

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

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

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

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

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

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

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

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

Answer 6

You need to custom your CHILD CoordinatorLayout, let it implement NestedScrollingChild (ori coordinatorlayout didn't implement it) and override some functions to enable dispatching nested scroll event to your PARENT CoordinatorLayout.