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      1 /*
      2  * Copyright (C) 2016 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 android.print;
     18 
     19 import android.annotation.NonNull;
     20 import android.content.Context;
     21 import android.content.Loader;
     22 import android.os.Handler;
     23 import android.os.Message;
     24 import android.printservice.recommendation.RecommendationInfo;
     25 
     26 import com.android.internal.util.Preconditions;
     27 
     28 import java.util.List;
     29 
     30 /**
     31  * Loader for the list of print service recommendations.
     32  *
     33  * @hide
     34  */
     35 public class PrintServiceRecommendationsLoader extends Loader<List<RecommendationInfo>> {
     36     /** The print manager to be used by this object */
     37     private final @NonNull PrintManager mPrintManager;
     38 
     39     /** Handler to sequentialize the delivery of the results to the main thread */
     40     private final @NonNull Handler mHandler;
     41 
     42     /** Listens for updates to the data from the platform */
     43     private PrintManager.PrintServiceRecommendationsChangeListener mListener;
     44 
     45     /**
     46      * Create a new PrintServicesLoader.
     47      *
     48      * @param printManager The print manager supplying the data
     49      * @param context      Context of the using object
     50      */
     51     public PrintServiceRecommendationsLoader(@NonNull PrintManager printManager,
     52             @NonNull Context context) {
     53         super(Preconditions.checkNotNull(context));
     54         mHandler = new MyHandler();
     55         mPrintManager = Preconditions.checkNotNull(printManager);
     56     }
     57 
     58     @Override
     59     protected void onForceLoad() {
     60         queueNewResult();
     61     }
     62 
     63     /**
     64      * Read the print service recommendations and queue it to be delivered on the main thread.
     65      */
     66     private void queueNewResult() {
     67         Message m = mHandler.obtainMessage(0);
     68         m.obj = mPrintManager.getPrintServiceRecommendations();
     69         mHandler.sendMessage(m);
     70     }
     71 
     72     @Override
     73     protected void onStartLoading() {
     74         mListener = new PrintManager.PrintServiceRecommendationsChangeListener() {
     75             @Override
     76             public void onPrintServiceRecommendationsChanged() {
     77                 queueNewResult();
     78             }
     79         };
     80 
     81         mPrintManager.addPrintServiceRecommendationsChangeListener(mListener, null);
     82 
     83         // Immediately deliver a result
     84         deliverResult(mPrintManager.getPrintServiceRecommendations());
     85     }
     86 
     87     @Override
     88     protected void onStopLoading() {
     89         if (mListener != null) {
     90             mPrintManager.removePrintServiceRecommendationsChangeListener(mListener);
     91             mListener = null;
     92         }
     93 
     94         mHandler.removeMessages(0);
     95     }
     96 
     97     @Override
     98     protected void onReset() {
     99         onStopLoading();
    100     }
    101 
    102     /**
    103      * Handler to sequentialize all the updates to the main thread.
    104      */
    105     private class MyHandler extends Handler {
    106         /**
    107          * Create a new handler on the main thread.
    108          */
    109         public MyHandler() {
    110             super(getContext().getMainLooper());
    111         }
    112 
    113         @Override
    114         public void handleMessage(Message msg) {
    115             if (isStarted()) {
    116                 deliverResult((List<RecommendationInfo>) msg.obj);
    117             }
    118         }
    119     }
    120 }
    121