/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.launcher3.util;
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import android.content.Context;
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import android.os.Handler;
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import android.view.LayoutInflater;
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import android.view.View;
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import android.view.ViewGroup;
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import com.android.launcher3.util.ViewPool.Reusable;
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import androidx.annotation.AnyThread;
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import androidx.annotation.Nullable;
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import androidx.annotation.UiThread;
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/**
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* Utility class to maintain a pool of reusable views.
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* During initialization, views are inflated on the background thread.
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*/
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public class ViewPool<T extends View & Reusable> {
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private final Object[] mPool;
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private final LayoutInflater mInflater;
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private final ViewGroup mParent;
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private final int mLayoutId;
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private int mCurrentSize = 0;
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public ViewPool(Context context, @Nullable ViewGroup parent,
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int layoutId, int maxSize, int initialSize) {
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mLayoutId = layoutId;
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mParent = parent;
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mInflater = LayoutInflater.from(context);
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mPool = new Object[maxSize];
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if (initialSize > 0) {
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initPool(initialSize);
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}
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}
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@UiThread
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private void initPool(int initialSize) {
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Preconditions.assertUIThread();
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Handler handler = new Handler();
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// Inflate views on a non looper thread. This allows us to catch errors like calling
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// "new Handler()" in constructor easily.
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new Thread(() -> {
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for (int i = 0; i < initialSize; i++) {
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T view = inflateNewView();
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handler.post(() -> addToPool(view));
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}
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}).start();
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}
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@UiThread
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public void recycle(T view) {
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Preconditions.assertUIThread();
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view.onRecycle();
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addToPool(view);
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}
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@UiThread
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private void addToPool(T view) {
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Preconditions.assertUIThread();
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if (mCurrentSize >= mPool.length) {
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// pool is full
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return;
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}
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mPool[mCurrentSize] = view;
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mCurrentSize++;
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}
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@UiThread
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public T getView() {
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Preconditions.assertUIThread();
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if (mCurrentSize > 0) {
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mCurrentSize--;
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return (T) mPool[mCurrentSize];
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}
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return inflateNewView();
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}
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@AnyThread
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private T inflateNewView() {
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return (T) mInflater.inflate(mLayoutId, mParent, false);
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}
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/**
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* Interface to indicate that a view is reusable
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*/
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public interface Reusable {
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/**
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* Called when a view is recycled / added back to the pool
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*/
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void onRecycle();
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}
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}
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