/*
* 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 android.view.ViewGroup;
import androidx.annotation.NonNull;
import androidx.core.view.ViewCompat.NestedScrollType;
import androidx.core.view.ViewCompat.ScrollAxis;
/**
* Helper class for implementing nested scrolling parent views compatible with Android platform
* versions earlier than Android 5.0 Lollipop (API 21).
*
* <p>{@link android.view.ViewGroup ViewGroup} subclasses should instantiate a final instance
* of this class as a field at construction. For each <code>ViewGroup</code> method that has
* a matching method signature in this class, delegate the operation to the helper instance
* in an overridden method implementation. This implements the standard framework policy
* for nested scrolling.</p>
*
* <p>Views invoking nested scrolling functionality should always do so from the relevant
* {@link androidx.core.view.ViewCompat}, {@link androidx.core.view.ViewGroupCompat} or
* {@link androidx.core.view.ViewParentCompat} compatibility
* shim static methods. This ensures interoperability with nested scrolling views on Android
* 5.0 Lollipop and newer.</p>
*/
public class NestedScrollingParentHelper {
private int mNestedScrollAxesTouch;
private int mNestedScrollAxesNonTouch;
/**
* Construct a new helper for a given ViewGroup
*/
public NestedScrollingParentHelper(@NonNull ViewGroup 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 androidx.core.view.NestedScrollingParent} interface method with
* the same signature to implement the standard policy.</p>
*/
public void onNestedScrollAccepted(@NonNull View child, @NonNull View target,
@ScrollAxis int axes) {
onNestedScrollAccepted(child, target, axes, ViewCompat.TYPE_TOUCH);
}
/**
* 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 androidx.core.view.NestedScrollingParent2} interface method with
* the same signature to implement the standard policy.</p>
*/
public void onNestedScrollAccepted(@NonNull View child, @NonNull View target,
@ScrollAxis int axes, @NestedScrollType int type) {
if (type == ViewCompat.TYPE_NON_TOUCH) {
mNestedScrollAxesNonTouch = axes;
} else {
mNestedScrollAxesTouch = 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 androidx.core.view.NestedScrollingParent} interface method with
* the same signature to implement the standard policy.</p>
*/
@ScrollAxis
public int getNestedScrollAxes() {
return mNestedScrollAxesTouch | mNestedScrollAxesNonTouch;
}
/**
* 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 androidx.core.view.NestedScrollingParent} interface method with
* the same signature to implement the standard policy.</p>
*/
public void onStopNestedScroll(@NonNull View target) {
onStopNestedScroll(target, ViewCompat.TYPE_TOUCH);
}
/**
* 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 androidx.core.view.NestedScrollingParent2} interface method with
* the same signature to implement the standard policy.</p>
*/
public void onStopNestedScroll(@NonNull View target, @NestedScrollType int type) {
if (type == ViewCompat.TYPE_NON_TOUCH) {
mNestedScrollAxesNonTouch = ViewGroup.SCROLL_AXIS_NONE;
} else {
mNestedScrollAxesTouch = ViewGroup.SCROLL_AXIS_NONE;
}
}
}