android 9.0 源码下载（28）

/* * 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.widget; import static androidx.annotation.RestrictTo.Scope.LIBRARY_GROUP; import static androidx.core.view.ViewCompat.TYPE_NON_TOUCH; import static androidx.core.view.ViewCompat.TYPE_TOUCH; import android.annotation.SuppressLint; import android.content.Context; import android.content.res.Resources; import android.content.res.TypedArray; import android.database.Observable; import android.graphics.Canvas; import android.graphics.Matrix; import android.graphics.PointF; import android.graphics.Rect; import android.graphics.RectF; import android.graphics.drawable.Drawable; import android.graphics.drawable.StateListDrawable; import android.os.Build; import android.os.Bundle; import android.os.Parcel; import android.os.Parcelable; import android.os.SystemClock; import android.util.AttributeSet; import android.util.Log; import android.util.SparseArray; import android.view.Display; import android.view.FocusFinder; import android.view.InputDevice; import android.view.MotionEvent; import android.view.VelocityTracker; import android.view.View; import android.view.ViewConfiguration; import android.view.ViewGroup; import android.view.ViewParent; import android.view.accessibility.AccessibilityEvent; import android.view.accessibility.AccessibilityManager; import android.view.animation.Interpolator; import android.widget.EdgeEffect; import android.widget.LinearLayout; import android.widget.OverScroller; import androidx.annotation.CallSuper; import androidx.annotation.IntDef; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.annotation.Px; import androidx.annotation.RestrictTo; import androidx.annotation.VisibleForTesting; import androidx.core.os.TraceCompat; import androidx.core.util.Preconditions; import androidx.core.view.InputDeviceCompat; import androidx.core.view.MotionEventCompat; import androidx.core.view.NestedScrollingChild2; import androidx.core.view.NestedScrollingChildHelper; import androidx.core.view.ScrollingView; import androidx.core.view.ViewCompat; import androidx.core.view.ViewConfigurationCompat; import androidx.core.view.accessibility.AccessibilityEventCompat; import androidx.core.view.accessibility.AccessibilityNodeInfoCompat; import androidx.core.widget.EdgeEffectCompat; import androidx.customview.view.AbsSavedState; import androidx.recyclerview.R; import androidx.recyclerview.widget.RecyclerView.ItemAnimator.ItemHolderInfo; import androidx.viewpager.widget.ViewPager; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.ref.WeakReference; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.util.ArrayList; import java.util.Collections; import java.util.List; /** * A flexible view for providing a limited window into a large data set. * * <h3>Glossary of terms:</h3> * * <ul> * <li><em>Adapter:</em> A subclass of {@link Adapter} responsible for providing views * that represent items in a data set.</li> * <li><em>Position:</em> The position of a data item within an <em>Adapter</em>.</li> * <li><em>Index:</em> The index of an attached child view as used in a call to * {@link ViewGroup#getChildAt}. Contrast with <em>Position.</em></li> * <li><em>Binding:</em> The process of preparing a child view to display data corresponding * to a <em>position</em> within the adapter.</li> * <li><em>Recycle (view):</em> A view previously used to display data for a specific adapter * position may be placed in a cache for later reuse to display the same type of data again * later. This can drastically improve performance by skipping initial layout inflation * or construction.</li> * <li><em>Scrap (view):</em> A child view that has entered into a temporarily detached * state during layout. Scrap views may be reused without becoming fully detached * from the parent RecyclerView, either unmodified if no rebinding is required or modified * by the adapter if the view was considered <em>dirty</em>.</li> * <li><em>Dirty (view):</em> A child view that must be rebound by the adapter before * being displayed.</li> * </ul> * * <h4>Positions in RecyclerView:</h4> * <p> * RecyclerView introduces an additional level of abstraction between the {@link Adapter} and * {@link LayoutManager} to be able to detect data set changes in batches during a layout * calculation. This saves LayoutManager from tracking adapter changes to calculate animations. * It also helps with performance because all view bindings happen at the same time and unnecessary * bindings are avoided. * <p> * For this reason, there are two types of <code>position</code> related methods in RecyclerView: * <ul> * <li>layout position: Position of an item in the latest layout calculation. This is the * position from the LayoutManager's perspective.</li> * <li>adapter position: Position of an item in the adapter. This is the position from * the Adapter's perspective.</li> * </ul> * <p> * These two positions are the same except the time between dispatching <code>adapter.notify* * </code> events and calculating the updated layout. * <p> * Methods that return or receive <code>*LayoutPosition*</code> use position as of the latest * layout calculation (e.g. {@link ViewHolder#getLayoutPosition()}, * {@link #findViewHolderForLayoutPosition(int)}). These positions include all changes until the * last layout calculation. You can rely on these positions to be consistent with what user is * currently seeing on the screen. For example, if you have a list of items on the screen and user * asks for the 5^th element, you should use these methods as they'll match what user * is seeing. * <p> * The other set of position related methods are in the form of * <code>*AdapterPosition*</code>. (e.g. {@link ViewHolder#getAdapterPosition()}, * {@link #findViewHolderForAdapterPosition(int)}) You should use these methods when you need to * work with up-to-date adapter positions even if they may not have been reflected to layout yet. * For example, if you want to access the item in the adapter on a ViewHolder click, you should use * {@link ViewHolder#getAdapterPosition()}. Beware that these methods may not be able to calculate * adapter positions if {@link Adapter#notifyDataSetChanged()} has been called and new layout has * not yet been calculated. For this reasons, you should carefully handle {@link #NO_POSITION} or * <code>null</code> results from these methods. * <p> * When writing a {@link LayoutManager} you almost always want to use layout positions whereas when * writing an {@link Adapter}, you probably want to use adapter positions. * * @attr ref androidx.recyclerview.R.styleable#RecyclerView_layoutManager */ public class RecyclerView extends ViewGroup implements ScrollingView, NestedScrollingChild2 { static final String TAG = "RecyclerView"; static final boolean DEBUG = false; static final boolean VERBOSE_TRACING = false; private static final int[] NESTED_SCROLLING_ATTRS = {16843830 /* android.R.attr.nestedScrollingEnabled */}; private static final int[] CLIP_TO_PADDING_ATTR = {android.R.attr.clipToPadding}; /** * On Kitkat and JB MR2, there is a bug which prevents