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/*
* Copyright (C) 2017 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 com.android.internal.widget;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import java.util.ArrayList;
import java.util.List;
/**
* Helper class to manage children.
*
* It wraps a RecyclerView and adds ability to hide some children. There are two sets of methods
* provided by this class. Regular methods are the ones that replicate ViewGroup methods
* like getChildAt, getChildCount etc. These methods ignore hidden children.
*
* When RecyclerView needs direct access to the view group children, it can call unfiltered
* methods like get getUnfilteredChildCount or getUnfilteredChildAt.
*/
class ChildHelper {
private static final boolean DEBUG = false;
private static final String TAG = "ChildrenHelper";
final Callback mCallback;
final Bucket mBucket;
final List mHiddenViews;
ChildHelper(Callback callback) {
mCallback = callback;
mBucket = new Bucket();
mHiddenViews = new ArrayList();
}
/**
* Marks a child view as hidden
*
* @param child View to hide.
*/
private void hideViewInternal(View child) {
mHiddenViews.add(child);
mCallback.onEnteredHiddenState(child);
}
/**
* Unmarks a child view as hidden.
*
* @param child View to hide.
*/
private boolean unhideViewInternal(View child) {
if (mHiddenViews.remove(child)) {
mCallback.onLeftHiddenState(child);
return true;
} else {
return false;
}
}
/**
* Adds a view to the ViewGroup
*
* @param child View to add.
* @param hidden If set to true, this item will be invisible from regular methods.
*/
void addView(View child, boolean hidden) {
addView(child, -1, hidden);
}
/**
* Add a view to the ViewGroup at an index
*
* @param child View to add.
* @param index Index of the child from the regular perspective (excluding hidden views).
* ChildHelper offsets this index to actual ViewGroup index.
* @param hidden If set to true, this item will be invisible from regular methods.
*/
void addView(View child, int index, boolean hidden) {
final int offset;
if (index < 0) {
offset = mCallback.getChildCount();
} else {
offset = getOffset(index);
}
mBucket.insert(offset, hidden);
if (hidden) {
hideViewInternal(child);
}
mCallback.addView(child, offset);
if (DEBUG) {
Log.d(TAG, "addViewAt " + index + ",h:" + hidden + ", " + this);
}
}
private int getOffset(int index) {
if (index < 0) {
return -1; //anything below 0 won't work as diff will be undefined.
}
final int limit = mCallback.getChildCount();
int offset = index;
while (offset < limit) {
final int removedBefore = mBucket.countOnesBefore(offset);
final int diff = index - (offset - removedBefore);
if (diff == 0) {
while (mBucket.get(offset)) { // ensure this offset is not hidden
offset++;
}
return offset;
} else {
offset += diff;
}
}
return -1;
}
/**
* Removes the provided View from underlying RecyclerView.
*
* @param view The view to remove.
*/
void removeView(View view) {
int index = mCallback.indexOfChild(view);
if (index < 0) {
return;
}
if (mBucket.remove(index)) {
unhideViewInternal(view);
}
mCallback.removeViewAt(index);
if (DEBUG) {
Log.d(TAG, "remove View off:" + index + "," + this);
}
}
/**
* Removes the view at the provided index from RecyclerView.
*
* @param index Index of the child from the regular perspective (excluding hidden views).
* ChildHelper offsets this index to actual ViewGroup index.
*/
void removeViewAt(int index) {
final int offset = getOffset(index);
final View view = mCallback.getChildAt(offset);
if (view == null) {
return;
}
if (mBucket.remove(offset)) {
unhideViewInternal(view);
}
mCallback.removeViewAt(offset);
if (DEBUG) {
Log.d(TAG, "removeViewAt " + index + ", off:" + offset + ", " + this);
}
}
/**
* Returns the child at provided index.
*
* @param index Index of the child to return in regular perspective.
*/
View getChildAt(int index) {
final int offset = getOffset(index);
return mCallback.getChildAt(offset);
}
/**
* Removes all views from the ViewGroup including the hidden ones.
*/
void removeAllViewsUnfiltered() {
mBucket.reset();
for (int i = mHiddenViews.size() - 1; i >= 0; i--) {
mCallback.onLeftHiddenState(mHiddenViews.get(i));
mHiddenViews.remove(i);
}
mCallback.removeAllViews();
if (DEBUG) {
Log.d(TAG, "removeAllViewsUnfiltered");
}
}
/**
* This can be used to find a disappearing view by position.
*
* @param position The adapter position of the item.
* @return A hidden view with a valid ViewHolder that matches the position.
*/
View findHiddenNonRemovedView(int position) {
final int count = mHiddenViews.size();
for (int i = 0; i < count; i++) {
final View view = mHiddenViews.get(i);
RecyclerView.ViewHolder holder = mCallback.getChildViewHolder(view);
if (holder.getLayoutPosition() == position
&& !holder.isInvalid()
&& !holder.isRemoved()) {
return view;
}
}
return null;
}
/**
* Attaches the provided view to the underlying ViewGroup.
*
* @param child Child to attach.
* @param index Index of the child to attach in regular perspective.
* @param layoutParams LayoutParams for the child.
* @param hidden If set to true, this item will be invisible to the regular methods.
*/
void attachViewToParent(View child, int index, ViewGroup.LayoutParams layoutParams,
boolean hidden) {
final int offset;
if (index < 0) {
offset = mCallback.getChildCount();
} else {
offset = getOffset(index);
}
mBucket.insert(offset, hidden);
if (hidden) {
hideViewInternal(child);
}
mCallback.attachViewToParent(child, offset, layoutParams);
if (DEBUG) {
Log.d(TAG, "attach view to parent index:" + index + ",off:" + offset + ","
+ "h:" + hidden + ", " + this);
}
}
/**
* Returns the number of children that are not hidden.
*
* @return Number of children that are not hidden.
* @see #getChildAt(int)
*/
int getChildCount() {
return mCallback.getChildCount() - mHiddenViews.size();
}
/**
* Returns the total number of children.
*
* @return The total number of children including the hidden views.
* @see #getUnfilteredChildAt(int)
*/
int getUnfilteredChildCount() {
return mCallback.getChildCount();
}
/**
* Returns a child by ViewGroup offset. ChildHelper won't offset this index.
*
* @param index ViewGroup index of the child to return.
* @return The view in the provided index.
*/
View getUnfilteredChildAt(int index) {
return mCallback.getChildAt(index);
}
/**
* Detaches the view at the provided index.
*
* @param index Index of the child to return in regular perspective.
*/
void detachViewFromParent(int index) {
final int offset = getOffset(index);
mBucket.remove(offset);
mCallback.detachViewFromParent(offset);
if (DEBUG) {
Log.d(TAG, "detach view from parent " + index + ", off:" + offset);
}
}
/**
* Returns the index of the child in regular perspective.
*
* @param child The child whose index will be returned.
* @return The regular perspective index of the child or -1 if it does not exists.
*/
int indexOfChild(View child) {
final int index = mCallback.indexOfChild(child);
if (index == -1) {
return -1;
}
if (mBucket.get(index)) {
if (DEBUG) {
throw new IllegalArgumentException("cannot get index of a hidden child");
} else {
return -1;
}
}
// reverse the index
return index - mBucket.countOnesBefore(index);
}
/**
* Returns whether a View is visible to LayoutManager or not.
*
* @param view The child view to check. Should be a child of the Callback.
* @return True if the View is not visible to LayoutManager
*/
boolean isHidden(View view) {
return mHiddenViews.contains(view);
}
/**
* Marks a child view as hidden.
*
* @param view The view to hide.
*/
void hide(View view) {
final int offset = mCallback.indexOfChild(view);
if (offset < 0) {
throw new IllegalArgumentException("view is not a child, cannot hide " + view);
}
if (DEBUG && mBucket.get(offset)) {
throw new RuntimeException("trying to hide same view twice, how come ? " + view);
}
mBucket.set(offset);
hideViewInternal(view);
if (DEBUG) {
Log.d(TAG, "hiding child " + view + " at offset " + offset + ", " + this);
}
}
/**
* Moves a child view from hidden list to regular list.
* Calling this method should probably be followed by a detach, otherwise, it will suddenly
* show up in LayoutManager's children list.
*
* @param view The hidden View to unhide
*/
void unhide(View view) {
final int offset = mCallback.indexOfChild(view);
if (offset < 0) {
throw new IllegalArgumentException("view is not a child, cannot hide " + view);
}
if (!mBucket.get(offset)) {
throw new RuntimeException("trying to unhide a view that was not hidden" + view);
}
mBucket.clear(offset);
unhideViewInternal(view);
}
@Override
public String toString() {
return mBucket.toString() + ", hidden list:" + mHiddenViews.size();
}
/**
* Removes a view from the ViewGroup if it is hidden.
*
* @param view The view to remove.
* @return True if the View is found and it is hidden. False otherwise.
*/
boolean removeViewIfHidden(View view) {
final int index = mCallback.indexOfChild(view);
if (index == -1) {
if (unhideViewInternal(view) && DEBUG) {
throw new IllegalStateException("view is in hidden list but not in view group");
}
return true;
}
if (mBucket.get(index)) {
mBucket.remove(index);
if (!unhideViewInternal(view) && DEBUG) {
throw new IllegalStateException(
"removed a hidden view but it is not in hidden views list");
}
mCallback.removeViewAt(index);
return true;
}
return false;
}
/**
* Bitset implementation that provides methods to offset indices.
*/
static class Bucket {
static final int BITS_PER_WORD = Long.SIZE;
static final long LAST_BIT = 1L << (Long.SIZE - 1);
long mData = 0;
Bucket mNext;
void set(int index) {
if (index >= BITS_PER_WORD) {
ensureNext();
mNext.set(index - BITS_PER_WORD);
} else {
mData |= 1L << index;
}
}
private void ensureNext() {
if (mNext == null) {
mNext = new Bucket();
}
}
void clear(int index) {
if (index >= BITS_PER_WORD) {
if (mNext != null) {
mNext.clear(index - BITS_PER_WORD);
}
} else {
mData &= ~(1L << index);
}
}
boolean get(int index) {
if (index >= BITS_PER_WORD) {
ensureNext();
return mNext.get(index - BITS_PER_WORD);
} else {
return (mData & (1L << index)) != 0;
}
}
void reset() {
mData = 0;
if (mNext != null) {
mNext.reset();
}
}
void insert(int index, boolean value) {
if (index >= BITS_PER_WORD) {
ensureNext();
mNext.insert(index - BITS_PER_WORD, value);
} else {
final boolean lastBit = (mData & LAST_BIT) != 0;
long mask = (1L << index) - 1;
final long before = mData & mask;
final long after = ((mData & ~mask)) << 1;
mData = before | after;
if (value) {
set(index);
} else {
clear(index);
}
if (lastBit || mNext != null) {
ensureNext();
mNext.insert(0, lastBit);
}
}
}
boolean remove(int index) {
if (index >= BITS_PER_WORD) {
ensureNext();
return mNext.remove(index - BITS_PER_WORD);
} else {
long mask = (1L << index);
final boolean value = (mData & mask) != 0;
mData &= ~mask;
mask = mask - 1;
final long before = mData & mask;
// cannot use >> because it adds one.
final long after = Long.rotateRight(mData & ~mask, 1);
mData = before | after;
if (mNext != null) {
if (mNext.get(0)) {
set(BITS_PER_WORD - 1);
}
mNext.remove(0);
}
return value;
}
}
int countOnesBefore(int index) {
if (mNext == null) {
if (index >= BITS_PER_WORD) {
return Long.bitCount(mData);
}
return Long.bitCount(mData & ((1L << index) - 1));
}
if (index < BITS_PER_WORD) {
return Long.bitCount(mData & ((1L << index) - 1));
} else {
return mNext.countOnesBefore(index - BITS_PER_WORD) + Long.bitCount(mData);
}
}
@Override
public String toString() {
return mNext == null ? Long.toBinaryString(mData)
: mNext.toString() + "xx" + Long.toBinaryString(mData);
}
}
interface Callback {
int getChildCount();
void addView(View child, int index);
int indexOfChild(View view);
void removeViewAt(int index);
View getChildAt(int offset);
void removeAllViews();
RecyclerView.ViewHolder getChildViewHolder(View view);
void attachViewToParent(View child, int index, ViewGroup.LayoutParams layoutParams);
void detachViewFromParent(int offset);
void onEnteredHiddenState(View child);
void onLeftHiddenState(View child);
}
}