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 MetadataLoader(Context context, Uri uri)40 MetadataLoader(Context context, Uri uri) { 41 super(context); 42 mContext = context; 43 mUri = uri; 44 } 45 46 @Override loadInBackground()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 onStartLoading()58 protected void onStartLoading() { 59 if (mMetadata != null) { 60 deliverResult(mMetadata); 61 } 62 if (takeContentChanged() || mMetadata == null) { 63 forceLoad(); 64 } 65 } 66 67 @Override deliverResult(Bundle metadata)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 onStopLoading()82 protected void onStopLoading() { 83 // Attempt to cancel the current load task if possible. 84 cancelLoad(); 85 } 86 87 @Override onReset()88 protected void onReset() { 89 super.onReset(); 90 91 // Ensure the loader is stopped 92 onStopLoading(); 93 94 mMetadata = null; 95 } 96 } 97