/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package androidx.core.view;
import android.view.View;
import androidx.annotation.NonNull;
/**
* This interface should be implemented by {@link android.view.ViewGroup ViewGroup} subclasses
* that wish to support scrolling operations delegated by a nested child view.
*
* <p>Classes implementing this interface should create a final instance of a
* {@link NestedScrollingParentHelper} as a field and delegate any View or ViewGroup methods
* to the <code>NestedScrollingParentHelper</code> methods of the same signature.</p>
*
* <p>Views invoking nested scrolling functionality should always do so from the relevant
* {@link ViewCompat}, {@link ViewGroupCompat} or {@link ViewParentCompat} compatibility
* shim static methods. This ensures interoperability with nested scrolling views on all versions
* of Android.</p>
*/
public interface NestedScrollingParent3 extends NestedScrollingParent2 {
/**
* React to a nested scroll in progress.
*
* <p>This method will be called when the ViewParent's current nested scrolling child view
* dispatches a nested scroll event. To receive calls to this method the ViewParent must have
* previously returned <code>true</code> for a call to
* {@link #onStartNestedScroll(View, View, int, int)}.
*
* <p>Both the consumed and unconsumed portions of the scroll distance are reported to the
* ViewParent. An implementation may choose to use the consumed portion to match or chase scroll
* position of multiple child elements, for example. The unconsumed portion may be used to
* allow continuous dragging of multiple scrolling or draggable elements, such as scrolling
* a list within a vertical drawer where the drawer begins dragging once the edge of inner
* scrolling content is reached.
*
* <p>This method is called when a nested scrolling child invokes
* {@link NestedScrollingChild3#dispatchNestedScroll(int, int, int, int, int[], int, int[])}} or
* one of methods it overloads.
*
* <p>An implementation must report how many pixels of the the x and y scroll distances were
* consumed by this nested scrolling parent by adding the consumed distances to the
* <code>consumed</code> parameter. If this View also implements {@link NestedScrollingChild3},
* <code>consumed</code> should also be passed up to it's nested scrolling parent so that the
* parent may also add any scroll distance it consumes. Index 0 corresponds to dx and index 1
* corresponds to dy.
*
* @param target The descendant view controlling the nested scroll
* @param dxConsumed Horizontal scroll distance in pixels already consumed by target
* @param dyConsumed Vertical scroll distance in pixels already consumed by target
* @param dxUnconsumed Horizontal scroll distance in pixels not consumed by target
* @param dyUnconsumed Vertical scroll distance in pixels not consumed by target
* @param type the type of input which cause this scroll event
* @param consumed Output. Upon this method returning, will contain the scroll
* distances consumed by this nested scrolling parent and the scroll distances
* consumed by any other parent up the view hierarchy
*
* @see NestedScrollingChild3#dispatchNestedScroll(int, int, int, int, int[], int, int[])
*/
void onNestedScroll(@NonNull View target, int dxConsumed, int dyConsumed, int dxUnconsumed,
int dyUnconsumed, @ViewCompat.NestedScrollType int type, @NonNull int[] consumed);
}