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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.launcher2;
     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 import java.util.LinkedList;
     25 import java.util.ListIterator;
     26 
     27 /**
     28  * Queue of things to run on a looper thread.  Items posted with {@link #post} will not
     29  * be actually enqued on the handler until after the last one has run, to keep from
     30  * starving the thread.
     31  *
     32  * This class is fifo.
     33  */
     34 public class DeferredHandler {
     35     private LinkedList<Pair<Runnable, Integer>> mQueue = new LinkedList<Pair<Runnable, Integer>>();
     36     private MessageQueue mMessageQueue = Looper.myQueue();
     37     private Impl mHandler = new Impl();
     38 
     39     private class Impl extends Handler implements MessageQueue.IdleHandler {
     40         public void handleMessage(Message msg) {
     41             Pair<Runnable, Integer> p;
     42             Runnable r;
     43             synchronized (mQueue) {
     44                 if (mQueue.size() == 0) {
     45                     return;
     46                 }
     47                 p = mQueue.removeFirst();
     48                 r = p.first;
     49             }
     50             r.run();
     51             synchronized (mQueue) {
     52                 scheduleNextLocked();
     53             }
     54         }
     55 
     56         public boolean queueIdle() {
     57             handleMessage(null);
     58             return false;
     59         }
     60     }
     61 
     62     private class IdleRunnable implements Runnable {
     63         Runnable mRunnable;
     64 
     65         IdleRunnable(Runnable r) {
     66             mRunnable = r;
     67         }
     68 
     69         public void run() {
     70             mRunnable.run();
     71         }
     72     }
     73 
     74     public DeferredHandler() {
     75     }
     76 
     77     /** Schedule runnable to run after everything that's on the queue right now. */
     78     public void post(Runnable runnable) {
     79         post(runnable, 0);
     80     }
     81     public void post(Runnable runnable, int type) {
     82         synchronized (mQueue) {
     83             mQueue.add(new Pair<Runnable, Integer>(runnable, type));
     84             if (mQueue.size() == 1) {
     85                 scheduleNextLocked();
     86             }
     87         }
     88     }
     89 
     90     /** Schedule runnable to run when the queue goes idle. */
     91     public void postIdle(final Runnable runnable) {
     92         postIdle(runnable, 0);
     93     }
     94     public void postIdle(final Runnable runnable, int type) {
     95         post(new IdleRunnable(runnable), type);
     96     }
     97 
     98     public void cancelRunnable(Runnable runnable) {
     99         synchronized (mQueue) {
    100             while (mQueue.remove(runnable)) { }
    101         }
    102     }
    103     public void cancelAllRunnablesOfType(int type) {
    104         synchronized (mQueue) {
    105             ListIterator<Pair<Runnable, Integer>> iter = mQueue.listIterator();
    106             Pair<Runnable, Integer> p;
    107             while (iter.hasNext()) {
    108                 p = iter.next();
    109                 if (p.second == type) {
    110                     iter.remove();
    111                 }
    112             }
    113         }
    114     }
    115 
    116     public void cancel() {
    117         synchronized (mQueue) {
    118             mQueue.clear();
    119         }
    120     }
    121 
    122     /** Runs all queued Runnables from the calling thread. */
    123     public void flush() {
    124         LinkedList<Pair<Runnable, Integer>> queue = new LinkedList<Pair<Runnable, Integer>>();
    125         synchronized (mQueue) {
    126             queue.addAll(mQueue);
    127             mQueue.clear();
    128         }
    129         for (Pair<Runnable, Integer> p : queue) {
    130             p.first.run();
    131         }
    132     }
    133 
    134     void scheduleNextLocked() {
    135         if (mQueue.size() > 0) {
    136             Pair<Runnable, Integer> p = mQueue.getFirst();
    137             Runnable peek = p.first;
    138             if (peek instanceof IdleRunnable) {
    139                 mMessageQueue.addIdleHandler(mHandler);
    140             } else {
    141                 mHandler.sendEmptyMessage(1);
    142             }
    143         }
    144     }
    145 }
    146 
    147