1 /* 2 * Copyright (C) 2020 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 17 package com.android.layoutlib.bridge.util; 18 19 import com.android.tools.layoutlib.annotations.NotNull; 20 import com.android.tools.layoutlib.annotations.Nullable; 21 22 import android.os.Handler; 23 import android.util.Pair; 24 25 import java.util.LinkedList; 26 import java.util.WeakHashMap; 27 28 /** 29 * A queue that stores {@link Runnable}s associated with the corresponding {@link Handler}s. 30 * {@link Runnable}s get automatically released when the corresponding {@link Handler} gets 31 * collected by the garbage collector. All {@link Runnable}s are queued in a single virtual queue 32 * with respect to their corresponding uptime (the time when they should be executed). 33 */ 34 public class HandlerMessageQueue { 35 private final WeakHashMap<Handler, LinkedList<Pair<Long, Runnable>>> runnablesMap = 36 new WeakHashMap<>(); 37 38 /** 39 * Adds a {@link Runnable} associated with the {@link Handler} to be executed at 40 * particular time 41 * @param h handler associated with the {@link Runnable} 42 * @param uptimeMillis time in milliseconds the {@link Runnable} to be executed 43 * @param r {@link Runnable} to be added 44 */ add(@otNull Handler h, long uptimeMillis, @NotNull Runnable r)45 public void add(@NotNull Handler h, long uptimeMillis, @NotNull Runnable r) { 46 LinkedList<Pair<Long, Runnable>> runnables = runnablesMap.computeIfAbsent(h, 47 k -> new LinkedList<>()); 48 49 int idx = 0; 50 while (idx < runnables.size()) { 51 if (runnables.get(idx).first <= uptimeMillis) { 52 idx++; 53 } else { 54 break; 55 } 56 } 57 runnables.add(idx, Pair.create(uptimeMillis, r)); 58 } 59 60 private static class HandlerWrapper { 61 public Handler handler; 62 } 63 64 /** 65 * Removes from the queue and returns the {@link Runnable} with the smallest uptime if it 66 * is less than the one passed as a parameter or null if such runnable does not exist. 67 * @param uptimeMillis 68 * @return the {@link Runnable} from the queue 69 */ 70 @Nullable extractFirst(long uptimeMillis)71 public Runnable extractFirst(long uptimeMillis) { 72 final HandlerWrapper w = new HandlerWrapper(); 73 runnablesMap.forEach((h, l) -> { 74 if (!l.isEmpty()) { 75 long currentUptime = l.getFirst().first; 76 if (currentUptime <= uptimeMillis) { 77 if (w.handler == null || currentUptime < 78 runnablesMap.get(w.handler).getFirst().first) { 79 w.handler = h; 80 } 81 } 82 } 83 }); 84 if (w.handler != null) { 85 return runnablesMap.get(w.handler).pollFirst().second; 86 } 87 return null; 88 } 89 90 /** 91 * @return true is queue has no runnables left 92 */ isNotEmpty()93 public boolean isNotEmpty() { 94 return runnablesMap.values().stream().anyMatch(l -> !l.isEmpty()); 95 } 96 97 /** 98 * @return number of runnables in the queue 99 */ size()100 public int size() { 101 return runnablesMap.values().stream().mapToInt(LinkedList::size).sum(); 102 } 103 104 /** 105 * Completely clears the entire queue 106 */ clear()107 public void clear() { 108 runnablesMap.clear(); 109 } 110 } 111