NestedScrollView

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1.NestedScrollingChild

public interface NestedScrollingChild {
@Override
    public void setNestedScrollingEnabled(boolean enabled) {
    }
    @Override
    public boolean isNestedScrollingEnabled() {
        return false;
    }
    @Override
    public boolean startNestedScroll(int axes) {
        return false;
    }
    @Override
    public void stopNestedScroll() {
    }
    @Override
    public boolean hasNestedScrollingParent() {
        return false;
    }
    @Override
    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
        return false;
    }
    @Override
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
        return false;
    }
    @Override
    public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
        return false;
    }
    @Override
    public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
        return false;
    }
}

2.NestedScrollingParent

public interface NestedScrollingParent {
public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
        return false;
    }
    @Override
    public void onNestedScrollAccepted(View child, View target, int nestedScrollAxes) {
    }

    @Override
    public void onStopNestedScroll(View target) {
    }

    @Override
    public void onNestedScroll(View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
    }
    @Override
    public void onNestedPreScroll(View target, int dx, int dy, int[] consumed) {
    }

    @Override
    public boolean onNestedFling(View target, float velocityX, float velocityY, boolean consumed) {
        return false;
    }
    @Override
    public boolean onNestedPreFling(View target, float velocityX, float velocityY) {
        return false;
    }
    @Override
    public int getNestedScrollAxes() {
        return 0;
    }
}

3.NestedScrollingChildHelper

public class NestedScrollingChildHelper {
    private final View mView;
    private ViewParent mNestedScrollingParent;
    private boolean mIsNestedScrollingEnabled;
    private int[] mTempNestedScrollConsumed;

    /**
     * Construct a new helper for a given view.
     */
    public NestedScrollingChildHelper(View view) {
        mView = view;
    }

    /**
     * Enable nested scrolling.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @param enabled true to enable nested scrolling dispatch from this view, false otherwise
     */
    public void setNestedScrollingEnabled(boolean enabled) {
        if (mIsNestedScrollingEnabled) {
            ViewCompat.stopNestedScroll(mView);
        }
        mIsNestedScrollingEnabled = enabled;
    }

    /**
     * Check if nested scrolling is enabled for this view.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @return true if nested scrolling is enabled for this view
     */
    public boolean isNestedScrollingEnabled() {
        return mIsNestedScrollingEnabled;
    }

    /**
     * Check if this view has a nested scrolling parent view currently receiving events for
     * a nested scroll in progress.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @return true if this view has a nested scrolling parent, false otherwise
     */
    public boolean hasNestedScrollingParent() {
        return mNestedScrollingParent != null;
    }

    /**
     * Start a new nested scroll for this view.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @param axes Supported nested scroll axes.
     *             See {@link android.support.v4.view.NestedScrollingChild#startNestedScroll(int)}.
     * @return true if a cooperating parent view was found and nested scrolling started successfully
     */
    public boolean startNestedScroll(int axes) {
        if (hasNestedScrollingParent()) {
            // Already in progress
            return true;
        }
        if (isNestedScrollingEnabled()) {
            ViewParent p = mView.getParent();
            View child = mView;
            while (p != null) {
                if (ViewParentCompat.onStartNestedScroll(p, child, mView, axes)) {
                    mNestedScrollingParent = p;
                    ViewParentCompat.onNestedScrollAccepted(p, child, mView, axes);
                    return true;
                }
                if (p instanceof View) {
                    child = (View) p;
                }
                p = p.getParent();
            }
        }
        return false;
    }

    /**
     * Stop a nested scroll in progress.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     */
    public void stopNestedScroll() {
        if (mNestedScrollingParent != null) {
            ViewParentCompat.onStopNestedScroll(mNestedScrollingParent, mView);
            mNestedScrollingParent = null;
        }
    }

    /**
     * Dispatch one step of a nested scrolling operation to the current nested scrolling parent.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @return true if the parent consumed any of the nested scroll
     */
    public boolean dispatchNestedScroll(int dxConsumed, int dyConsumed,
            int dxUnconsumed, int dyUnconsumed, int[] offsetInWindow) {
        if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
            if (dxConsumed != 0 || dyConsumed != 0 || dxUnconsumed != 0 || dyUnconsumed != 0) {
                int startX = 0;
                int startY = 0;
                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    startX = offsetInWindow[0];
                    startY = offsetInWindow[1];
                }

                ViewParentCompat.onNestedScroll(mNestedScrollingParent, mView, dxConsumed,
                        dyConsumed, dxUnconsumed, dyUnconsumed);

                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    offsetInWindow[0] -= startX;
                    offsetInWindow[1] -= startY;
                }
                return true;
            } else if (offsetInWindow != null) {
                // No motion, no dispatch. Keep offsetInWindow up to date.
                offsetInWindow[0] = 0;
                offsetInWindow[1] = 0;
            }
        }
        return false;
    }

    /**
     * Dispatch one step of a nested pre-scrolling operation to the current nested scrolling parent.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @return true if the parent consumed any of the nested scroll
     */
    public boolean dispatchNestedPreScroll(int dx, int dy, int[] consumed, int[] offsetInWindow) {
        if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
            if (dx != 0 || dy != 0) {
                int startX = 0;
                int startY = 0;
                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    startX = offsetInWindow[0];
                    startY = offsetInWindow[1];
                }

                if (consumed == null) {
                    if (mTempNestedScrollConsumed == null) {
                        mTempNestedScrollConsumed = new int[2];
                    }
                    consumed = mTempNestedScrollConsumed;
                }
                consumed[0] = 0;
                consumed[1] = 0;
                ViewParentCompat.onNestedPreScroll(mNestedScrollingParent, mView, dx, dy, consumed);

                if (offsetInWindow != null) {
                    mView.getLocationInWindow(offsetInWindow);
                    offsetInWindow[0] -= startX;
                    offsetInWindow[1] -= startY;
                }
                return consumed[0] != 0 || consumed[1] != 0;
            } else if (offsetInWindow != null) {
                offsetInWindow[0] = 0;
                offsetInWindow[1] = 0;
            }
        }
        return false;
    }

    /**
     * Dispatch a nested fling operation to the current nested scrolling parent.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @return true if the parent consumed the nested fling
     */
    public boolean dispatchNestedFling(float velocityX, float velocityY, boolean consumed) {
        if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
            return ViewParentCompat.onNestedFling(mNestedScrollingParent, mView, velocityX,
                    velocityY, consumed);
        }
        return false;
    }

    /**
     * Dispatch a nested pre-fling operation to the current nested scrolling parent.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @return true if the parent consumed the nested fling
     */
    public boolean dispatchNestedPreFling(float velocityX, float velocityY) {
        if (isNestedScrollingEnabled() && mNestedScrollingParent != null) {
            return ViewParentCompat.onNestedPreFling(mNestedScrollingParent, mView, velocityX,
                    velocityY);
        }
        return false;
    }

    /**
     * View subclasses should always call this method on their
     * <code>NestedScrollingChildHelper</code> when detached from a window.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     */
    public void onDetachedFromWindow() {
        ViewCompat.stopNestedScroll(mView);
    }

    /**
     * Called when a nested scrolling child stops its current nested scroll operation.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.View View} subclass
     * method/{@link android.support.v4.view.NestedScrollingChild} interface method with the same
     * signature to implement the standard policy.</p>
     *
     * @param child Child view stopping its nested scroll. This may not be a direct child view.
     */
    public void onStopNestedScroll(View child) {
        ViewCompat.stopNestedScroll(mView);
    }
}

4.NestedScrollingParentHelper

public class NestedScrollingParentHelper {
    private final ViewGroup mViewGroup;
    private int mNestedScrollAxes;

    /**
     * Construct a new helper for a given ViewGroup
     */
    public NestedScrollingParentHelper(ViewGroup viewGroup) {
        mViewGroup = viewGroup;
    }

    /**
     * Called when a nested scrolling operation initiated by a descendant view is accepted
     * by this ViewGroup.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.ViewGroup ViewGroup}
     * subclass method/{@link android.support.v4.view.NestedScrollingParent} interface method with
     * the same signature to implement the standard policy.</p>
     */
    public void onNestedScrollAccepted(View child, View target, int axes) {
        mNestedScrollAxes = axes;
    }

    /**
     * Return the current axes of nested scrolling for this ViewGroup.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.ViewGroup ViewGroup}
     * subclass method/{@link android.support.v4.view.NestedScrollingParent} interface method with
     * the same signature to implement the standard policy.</p>
     */
    public int getNestedScrollAxes() {
        return mNestedScrollAxes;
    }

    /**
     * React to a nested scroll operation ending.
     *
     * <p>This is a delegate method. Call it from your {@link android.view.ViewGroup ViewGroup}
     * subclass method/{@link android.support.v4.view.NestedScrollingParent} interface method with
     * the same signature to implement the standard policy.</p>
     *
     * @param target View that initiated the nested scroll
     */
    public void onStopNestedScroll(View target) {
        mNestedScrollAxes = 0;
    }
}