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      1 /*
      2  * Copyright (C) 2012 Google Inc.
      3  * Licensed to The Android Open Source Project.
      4  *
      5  * Licensed under the Apache License, Version 2.0 (the "License");
      6  * you may not use this file except in compliance with the License.
      7  * You may obtain a copy of the License at
      8  *
      9  *      http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  * Unless required by applicable law or agreed to in writing, software
     12  * distributed under the License is distributed on an "AS IS" BASIS,
     13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  * See the License for the specific language governing permissions and
     15  * limitations under the License.
     16  */
     17 
     18 package com.android.mail.ui;
     19 
     20 import android.app.Activity;
     21 import android.app.FragmentTransaction;
     22 import android.os.Handler;
     23 
     24 import com.android.mail.utils.LogTag;
     25 import com.android.mail.utils.LogUtils;
     26 
     27 import java.util.concurrent.atomic.AtomicInteger;
     28 
     29 /**
     30  * A thin wrapper of {@link Handler} to run a callback in UI thread. Any callback posted to this
     31  * handler is guarantee to run inside {@link Activity} life cycle. However, it can be dropped if the
     32  * {@link Activity} has been stopped. This handler is safe to use with {@link FragmentTransaction}.
     33  *
     34  * @author phamm
     35  */
     36 public class UiHandler {
     37     private final Handler mHandler = new Handler();
     38     private boolean mEnabled = true;
     39     private final static String LOG_TAG = LogTag.getLogTag();
     40 
     41     /** Number of {@link Runnable} in the queue. */
     42     private AtomicInteger mCount = new AtomicInteger(0);
     43 
     44     public void post(final Runnable r) {
     45         if (mEnabled) {
     46             mCount.incrementAndGet();
     47             mHandler.post(new Runnable() {
     48                 @Override
     49                 public void run() {
     50                     mCount.decrementAndGet();
     51                     r.run();
     52                 }
     53             });
     54         } else {
     55             LogUtils.d(LOG_TAG, "UiHandler is disabled in post(). Dropping Runnable.");
     56         }
     57     }
     58 
     59     public void postDelayed(final Runnable r, long delayMillis) {
     60         if (mEnabled) {
     61             mCount.incrementAndGet();
     62             mHandler.postDelayed(new Runnable() {
     63                 @Override
     64                 public void run() {
     65                     mCount.decrementAndGet();
     66                     r.run();
     67                 }
     68             }, delayMillis);
     69         } else {
     70             LogUtils.d(LOG_TAG, "UiHandler is disabled in postDelayed(). Dropping Runnable.");
     71         }
     72     }
     73 
     74     public void removeCallbacks(Runnable r) {
     75         mHandler.removeCallbacks(r);
     76     }
     77 
     78     public void setEnabled(boolean enabled) {
     79         mEnabled = enabled;
     80         if (!mEnabled) {
     81             int count = mCount.getAndSet(0);
     82             if (count > 0) {
     83                 LogUtils.e(LOG_TAG, "Disable UiHandler. Dropping %d Runnables.", count);
     84             }
     85             mHandler.removeCallbacksAndMessages(null);
     86         }
     87     }
     88 
     89     /**
     90      * @return whether the {@link UiHandler} is enabled. It's safe to edit UI if the
     91      *         {@link UiHandler} is enabled.
     92      */
     93     public boolean isEnabled() {
     94         return mEnabled;
     95     }
     96 }