androidx/recyclerview/selection/PointerDragEventInterceptor.java

/*
 * 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.recyclerview.selection;

import static androidx.core.util.Preconditions.checkArgument;

import android.view.MotionEvent;

import androidx.annotation.Nullable;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.RecyclerView.OnItemTouchListener;

/**
 * OnItemTouchListener that delegates drag events to a drag listener,
 * else sends event to fallback {@link OnItemTouchListener}.
 *
 * <p>See {@link OnDragInitiatedListener} for details on implementing drag and drop.
 */
final class PointerDragEventInterceptor implements OnItemTouchListener {

    private final ItemDetailsLookup mEventDetailsLookup;
    private final OnDragInitiatedListener mDragListener;
    private @Nullable OnItemTouchListener mDelegate;

    PointerDragEventInterceptor(
            ItemDetailsLookup eventDetailsLookup,
            OnDragInitiatedListener dragListener,
            @Nullable OnItemTouchListener delegate) {

        checkArgument(eventDetailsLookup != null);
        checkArgument(dragListener != null);

        mEventDetailsLookup = eventDetailsLookup;
        mDragListener = dragListener;
        mDelegate = delegate;
    }

    @Override
    public boolean onInterceptTouchEvent(RecyclerView rv, MotionEvent e) {
        if (MotionEvents.isPointerDragEvent(e) && mEventDetailsLookup.inItemDragRegion(e)) {
            return mDragListener.onDragInitiated(e);
        } else if (mDelegate != null) {
            return mDelegate.onInterceptTouchEvent(rv, e);
        }
        return false;
    }

    @Override
    public void onTouchEvent(RecyclerView rv, MotionEvent e) {
        if (mDelegate != null) {
            mDelegate.onTouchEvent(rv, e);
        }
    }

    @Override
    public void onRequestDisallowInterceptTouchEvent(boolean disallowIntercept) {
        if (mDelegate != null) {
            mDelegate.onRequestDisallowInterceptTouchEvent(disallowIntercept);
        }
    }
}