1 /* 2 * Copyright (C) 2014 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 languag`e governing permissions and 14 * limitations under the License. 15 */ 16 17 package android.support.v7.widget; 18 import android.view.View; 19 20 /** 21 * Helper class that keeps temporary state while {LayoutManager} is filling out the empty 22 * space. 23 */ 24 class LayoutState { 25 26 final static String TAG = "LayoutState"; 27 28 final static int LAYOUT_START = -1; 29 30 final static int LAYOUT_END = 1; 31 32 final static int INVALID_LAYOUT = Integer.MIN_VALUE; 33 34 final static int ITEM_DIRECTION_HEAD = -1; 35 36 final static int ITEM_DIRECTION_TAIL = 1; 37 38 final static int SCOLLING_OFFSET_NaN = Integer.MIN_VALUE; 39 40 /** 41 * Number of pixels that we should fill, in the layout direction. 42 */ 43 int mAvailable; 44 45 /** 46 * Current position on the adapter to get the next item. 47 */ 48 int mCurrentPosition; 49 50 /** 51 * Defines the direction in which the data adapter is traversed. 52 * Should be {@link #ITEM_DIRECTION_HEAD} or {@link #ITEM_DIRECTION_TAIL} 53 */ 54 int mItemDirection; 55 56 /** 57 * Defines the direction in which the layout is filled. 58 * Should be {@link #LAYOUT_START} or {@link #LAYOUT_END} 59 */ 60 int mLayoutDirection; 61 62 /** 63 * Used if you want to pre-layout items that are not yet visible. 64 * The difference with {@link #mAvailable} is that, when recycling, distance rendered for 65 * {@link #mExtra} is not considered not to recycle visible children. 66 */ 67 int mExtra = 0; 68 69 /** 70 * @return true if there are more items in the data adapter 71 */ 72 boolean hasMore(RecyclerView.State state) { 73 return mCurrentPosition >= 0 && mCurrentPosition < state.getItemCount(); 74 } 75 76 /** 77 * Gets the view for the next element that we should render. 78 * Also updates current item index to the next item, based on {@link #mItemDirection} 79 * 80 * @return The next element that we should render. 81 */ 82 View next(RecyclerView.Recycler recycler) { 83 final View view = recycler.getViewForPosition(mCurrentPosition); 84 mCurrentPosition += mItemDirection; 85 return view; 86 } 87 } 88
