Home | History | Annotate | Download | only in launcher2 
      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.Log;
     24 
     25 import java.util.LinkedList;
     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<Runnable> mQueue = new LinkedList();
     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             Runnable r;
     42             synchronized (mQueue) {
     43                 if (mQueue.size() == 0) {
     44                     return;
     45                 }
     46                 r = mQueue.removeFirst();
     47             }
     48             r.run();
     49             synchronized (mQueue) {
     50                 scheduleNextLocked();
     51             }
     52         }
     53 
     54         public boolean queueIdle() {
     55             handleMessage(null);
     56             return false;
     57         }
     58     }
     59 
     60     private class IdleRunnable implements Runnable {
     61         Runnable mRunnable;
     62 
     63         IdleRunnable(Runnable r) {
     64             mRunnable = r;
     65         }
     66 
     67         public void run() {
     68             mRunnable.run();
     69         }
     70     }
     71 
     72     public DeferredHandler() {
     73     }
     74 
     75     /** Schedule runnable to run after everything that's on the queue right now. */
     76     public void post(Runnable runnable) {
     77         synchronized (mQueue) {
     78             mQueue.add(runnable);
     79             if (mQueue.size() == 1) {
     80                 scheduleNextLocked();
     81             }
     82         }
     83     }
     84 
     85     /** Schedule runnable to run when the queue goes idle. */
     86     public void postIdle(final Runnable runnable) {
     87         post(new IdleRunnable(runnable));
     88     }
     89 
     90     public void cancelRunnable(Runnable runnable) {
     91         synchronized (mQueue) {
     92             while (mQueue.remove(runnable)) { }
     93         }
     94     }
     95 
     96     public void cancel() {
     97         synchronized (mQueue) {
     98             mQueue.clear();
     99         }
    100     }
    101 
    102     void scheduleNextLocked() {
    103         if (mQueue.size() > 0) {
    104             Runnable peek = mQueue.getFirst();
    105             if (peek instanceof IdleRunnable) {
    106                 mMessageQueue.addIdleHandler(mHandler);
    107             } else {
    108                 mHandler.sendEmptyMessage(1);
    109             }
    110         }
    111     }
    112 }
    113 
    114