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      1 /*
      2  * Copyright (C) 2017 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 package com.android.documentsui.inspector;
     17 
     18 import android.content.AsyncTaskLoader;
     19 import android.content.Context;
     20 import android.net.Uri;
     21 import android.os.Bundle;
     22 import android.provider.DocumentsContract;
     23 import android.support.annotation.Nullable;
     24 import android.util.Log;
     25 
     26 import java.io.FileNotFoundException;
     27 
     28 /**
     29  * Loads metadata from {@link DocumentsContract#getDocumentMetadata(android.content.ContentProviderClient, Uri, String[])}
     30  */
     31 final class MetadataLoader extends AsyncTaskLoader<Bundle> {
     32 
     33     private static final String TAG = "MetadataLoader";
     34 
     35     private final Context mContext;
     36     private final Uri mUri;
     37 
     38     private @Nullable Bundle mMetadata;
     39 
     40     MetadataLoader(Context context, Uri uri) {
     41         super(context);
     42         mContext = context;
     43         mUri = uri;
     44     }
     45 
     46     @Override
     47     public Bundle loadInBackground() {
     48         try {
     49             return DocumentsContract.getDocumentMetadata(mContext.getContentResolver(), mUri);
     50         } catch (FileNotFoundException e) {
     51             Log.e(TAG, "Failed to load metadata for doc: " + mUri, e);
     52         }
     53 
     54         return null;
     55     }
     56 
     57     @Override
     58     protected void onStartLoading() {
     59         if (mMetadata != null) {
     60             deliverResult(mMetadata);
     61         }
     62         if (takeContentChanged() || mMetadata == null) {
     63             forceLoad();
     64         }
     65     }
     66 
     67     @Override
     68     public void deliverResult(Bundle metadata) {
     69         if (isReset()) {
     70             return;
     71         }
     72         mMetadata = metadata;
     73         if (isStarted()) {
     74             super.deliverResult(metadata);
     75         }
     76     }
     77 
     78     /**
     79      * Must be called from the UI thread
     80      */
     81     @Override
     82     protected void onStopLoading() {
     83         // Attempt to cancel the current load task if possible.
     84         cancelLoad();
     85     }
     86 
     87     @Override
     88     protected void onReset() {
     89         super.onReset();
     90 
     91         // Ensure the loader is stopped
     92         onStopLoading();
     93 
     94         mMetadata = null;
     95     }
     96 }
     97