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      1 /*
      2  * Copyright (C) 2008 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.launcher3;
     18 
     19 import android.os.Handler;
     20 import android.os.Looper;
     21 import android.os.Message;
     22 import android.os.MessageQueue;
     23 import android.util.Pair;
     24 
     25 import java.util.LinkedList;
     26 import java.util.ListIterator;
     27 
     28 /**
     29  * Queue of things to run on a looper thread.  Items posted with {@link #post} will not
     30  * be actually enqued on the handler until after the last one has run, to keep from
     31  * starving the thread.
     32  *
     33  * This class is fifo.
     34  */
     35 public class DeferredHandler {
     36     private LinkedList<Pair<Runnable, Integer>> mQueue = new LinkedList<Pair<Runnable, Integer>>();
     37     private MessageQueue mMessageQueue = Looper.myQueue();
     38     private Impl mHandler = new Impl();
     39 
     40     private class Impl extends Handler implements MessageQueue.IdleHandler {
     41         public void handleMessage(Message msg) {
     42             Pair<Runnable, Integer> p;
     43             Runnable r;
     44             synchronized (mQueue) {
     45                 if (mQueue.size() == 0) {
     46                     return;
     47                 }
     48                 p = mQueue.removeFirst();
     49                 r = p.first;
     50             }
     51             r.run();
     52             synchronized (mQueue) {
     53                 scheduleNextLocked();
     54             }
     55         }
     56 
     57         public boolean queueIdle() {
     58             handleMessage(null);
     59             return false;
     60         }
     61     }
     62 
     63     private class IdleRunnable implements Runnable {
     64         Runnable mRunnable;
     65 
     66         IdleRunnable(Runnable r) {
     67             mRunnable = r;
     68         }
     69 
     70         public void run() {
     71             mRunnable.run();
     72         }
     73     }
     74 
     75     public DeferredHandler() {
     76     }
     77 
     78     /** Schedule runnable to run after everything that's on the queue right now. */
     79     public void post(Runnable runnable) {
     80         post(runnable, 0);
     81     }
     82     public void post(Runnable runnable, int type) {
     83         synchronized (mQueue) {
     84             mQueue.add(new Pair<Runnable, Integer>(runnable, type));
     85             if (mQueue.size() == 1) {
     86                 scheduleNextLocked();
     87             }
     88         }
     89     }
     90 
     91     /** Schedule runnable to run when the queue goes idle. */
     92     public void postIdle(final Runnable runnable) {
     93         postIdle(runnable, 0);
     94     }
     95     public void postIdle(final Runnable runnable, int type) {
     96         post(new IdleRunnable(runnable), type);
     97     }
     98 
     99     public void cancelRunnable(Runnable runnable) {
    100         synchronized (mQueue) {
    101             while (mQueue.remove(runnable)) { }
    102         }
    103     }
    104     public void cancelAllRunnablesOfType(int type) {
    105         synchronized (mQueue) {
    106             ListIterator<Pair<Runnable, Integer>> iter = mQueue.listIterator();
    107             Pair<Runnable, Integer> p;
    108             while (iter.hasNext()) {
    109                 p = iter.next();
    110                 if (p.second == type) {
    111                     iter.remove();
    112                 }
    113             }
    114         }
    115     }
    116 
    117     public void cancel() {
    118         synchronized (mQueue) {
    119             mQueue.clear();
    120         }
    121     }
    122 
    123     /** Runs all queued Runnables from the calling thread. */
    124     public void flush() {
    125         LinkedList<Pair<Runnable, Integer>> queue = new LinkedList<Pair<Runnable, Integer>>();
    126         synchronized (mQueue) {
    127             queue.addAll(mQueue);
    128             mQueue.clear();
    129         }
    130         for (Pair<Runnable, Integer> p : queue) {
    131             p.first.run();
    132         }
    133     }
    134 
    135     void scheduleNextLocked() {
    136         if (mQueue.size() > 0) {
    137             Pair<Runnable, Integer> p = mQueue.getFirst();
    138             Runnable peek = p.first;
    139             if (peek instanceof IdleRunnable) {
    140                 mMessageQueue.addIdleHandler(mHandler);
    141             } else {
    142                 mHandler.sendEmptyMessage(1);
    143             }
    144         }
    145     }
    146 }
    147 
    148