1 /* 2 * Copyright 2018 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 18 package androidx.core.view; 19 20 import android.view.View; 21 22 import org.jspecify.annotations.NonNull; 23 import org.jspecify.annotations.Nullable; 24 25 /** 26 * This interface should be implemented by {@link View View} subclasses that wish 27 * to support dispatching nested scrolling operations to a cooperating parent 28 * {@link android.view.ViewGroup ViewGroup}. 29 * 30 * <p>Classes implementing this interface should create a final instance of a 31 * {@link NestedScrollingChildHelper} as a field and delegate any View methods to the 32 * <code>NestedScrollingChildHelper</code> methods of the same signature.</p> 33 * 34 * <p>Views invoking nested scrolling functionality should always do so from the relevant 35 * {@link ViewCompat}, {@link ViewGroupCompat} or {@link ViewParentCompat} compatibility 36 * shim static methods. This ensures interoperability with nested scrolling views on all versions 37 * of Android.</p> 38 */ 39 public interface NestedScrollingChild3 extends NestedScrollingChild2 { 40 41 /** 42 * Dispatch one step of a nested scroll in progress. 43 * 44 * <p>Implementations of views that support nested scrolling should call this to report 45 * info about a scroll in progress to the current nested scrolling parent. If a nested scroll 46 * is not currently in progress or nested scrolling is not 47 * {@link #isNestedScrollingEnabled() enabled} for this view this method does nothing. 48 * 49 * <p>Compatible View implementations should also call 50 * {@link #dispatchNestedPreScroll(int, int, int[], int[], int) dispatchNestedPreScroll} before 51 * consuming a component of the scroll event themselves. 52 * 53 * <p>The original nested scrolling child (where the input events were received to start the 54 * scroll) must provide a non-null <code>consumed</code> parameter with values {0, 0}. 55 * 56 * @param dxConsumed Horizontal distance in pixels consumed by this view during this scroll step 57 * @param dyConsumed Vertical distance in pixels consumed by this view during this scroll step 58 * @param dxUnconsumed Horizontal scroll distance in pixels not consumed by this view 59 * @param dyUnconsumed Horizontal scroll distance in pixels not consumed by this view 60 * @param offsetInWindow Optional. If not null, on return this will contain the offset 61 * in local view coordinates of this view from before this operation 62 * to after it completes. View implementations may use this to adjust 63 * expected input coordinate tracking. 64 * @param type the type of input which cause this scroll event 65 * @param consumed Output. Upon this method returning, will contain the original values plus any 66 * scroll distances consumed by all of this view's nested scrolling parents up 67 * the view hierarchy. Index 0 for the x dimension, and index 1 for the y 68 * dimension 69 * 70 * @see NestedScrollingParent3#onNestedScroll(View, int, int, int, int, int, int[]) 71 */ dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, int @Nullable [] offsetInWindow, @ViewCompat.NestedScrollType int type, int @NonNull [] consumed)72 void dispatchNestedScroll(int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed, 73 int @Nullable [] offsetInWindow, @ViewCompat.NestedScrollType int type, 74 int @NonNull [] consumed); 75 } 76