1 /* 2 * Copyright (C) 2017 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 package com.android.documentsui.selection; 17 18 import static android.support.v4.util.Preconditions.checkArgument; 19 20 import android.support.v7.widget.RecyclerView; 21 import android.view.MotionEvent; 22 import android.view.View; 23 24 /** 25 * Provides a means of controlling when and where band selection is initiated. 26 * This can be used to permit band initiation in non-empty areas, like in the whitespace of 27 * a bound view. This is especially useful when there is no empty space between items. 28 */ 29 public abstract class BandPredicate { 30 31 /** @return true if band selection can be initiated in response to the {@link MotionEvent}. */ canInitiate(MotionEvent e)32 public abstract boolean canInitiate(MotionEvent e); 33 34 /** 35 * A BandPredicate that allows initiation of band selection only in areas of RecyclerView 36 * that have {@link RecyclerView#NO_POSITION}. In most cases, this will be the empty areas 37 * between views. 38 */ 39 public static final class NoPositionBandPredicate extends BandPredicate { 40 41 private final RecyclerView mRecView; 42 NoPositionBandPredicate(RecyclerView recView)43 public NoPositionBandPredicate(RecyclerView recView) { 44 checkArgument(recView != null); 45 46 mRecView = recView; 47 } 48 49 @Override canInitiate(MotionEvent e)50 public boolean canInitiate(MotionEvent e) { 51 View itemView = mRecView.findChildViewUnder(e.getX(), e.getY()); 52 int position = itemView != null 53 ? mRecView.getChildAdapterPosition(itemView) 54 : RecyclerView.NO_POSITION; 55 56 return position == RecyclerView.NO_POSITION; 57 } 58 }; 59 } 60