Implement the new Photo picker, part two.

chrome/android/java/src/org/chromium/chrome/browser/photo_picker/FileEnumWorkerTask.java

+// Copyright 2016 The Chromium Authors. All rights reserved.

[Theresa, 2017/03/28 20:40:28]

s/2016/2017

[Finnur, 2017/03/31 14:26:49]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.chrome.browser.photo_picker;
+
+import android.os.AsyncTask;
+import android.os.Environment;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Locale;
+
+/**
+ * A worker task to enumerate image files on disk.
+ */
+class FileEnumWorkerTask extends AsyncTask<Void, Void, List<PickerBitmap>> {
+    /**
+     * An interface to use to communicate back the results to the client.
+     */
+    public interface FilesEnumeratedCallback {
+        /**
+         * A callback to define to receive the list of all images on disk.
+         * @param files The list of images.
+         */
+        void filesEnumeratedCallback(List<PickerBitmap> files);
+    }
+
+    // The callback to use to communicate the results.
+    private FilesEnumeratedCallback mCallback;
+
+    // The filter to apply to the list.
+    private AttrAcceptFileFilter mFilter;
+
+    /**
+     * A FileEnumWorkerTask constructor.
+     * @param callback The callback to use to communicate back the results.
+     * @param filter The file filter to apply to the list.
+     */
+    public FileEnumWorkerTask(FilesEnumeratedCallback callback, AttrAcceptFileFilter filter) {
+        mCallback = callback;
+        mFilter = filter;
+    }
+
+    /**
+     * Enumerates (in the background) the image files on disk. Called on a non-UI thread

[Theresa, 2017/03/28 20:40:28]

nit: Please add an assert to the method to check that this is a non-UI thread.
See ThreadUtils#runningOnUiThread().

[Finnur, 2017/03/31 14:26:49]

Done.

+     * @param params Ignored, do not use.
+     * @return A sorted list of images (by last-modified first).
+     */
+    @Override
+    protected List<PickerBitmap> doInBackground(Void... params) {
+        if (isCancelled()) {
+            return null;

[Theresa, 2017/03/28 20:40:28]

nit: inline above

if (isCancelled()) return null;

[Finnur, 2017/03/31 14:26:49]

Done.

+        }
+
+        List<PickerBitmap> pickerBitmaps = new ArrayList<>();
+
+        String paths[] = new String[3];
+        paths[0] = "/DCIM/Camera";

[Theresa, 2017/03/28 20:40:28]

How confident are we that the directories will be labeled this way? Maybe we
should look at the logic used in other apps (e.g. Google Photos) to make sure
we're finding images in a consistent way.

[Finnur, 2017/03/31 14:26:49]

Acknowledged. Will change it in a future CL, since I'm removing this file
shortly (from this CL).

+        paths[1] = "/Pictures/Screenshots";
+        paths[2] = "/Download";
+
+        for (int path = 0; path < paths.length; ++path) {
+            String filePath = Environment.getExternalStorageDirectory().toString() + paths[path];
+            File directory = new File(filePath);
+            File[] files = directory.listFiles(mFilter);
+            if (files == null) {
+                continue;
+            }
+
+            for (File file : files) {
+                if (isCancelled()) {
+                    return null;
+                }
+
+                if (isImageExtension(file.getName())) {
+                    pickerBitmaps.add(new PickerBitmap(filePath + "/" + file.getName(),
+                            file.lastModified(), PickerBitmap.TileTypes.PICTURE));
+                }
+            }
+        }
+
+        Collections.sort(pickerBitmaps);
+
+        pickerBitmaps.add(0, new PickerBitmap("", 0, PickerBitmap.TileTypes.GALLERY));
+        pickerBitmaps.add(0, new PickerBitmap("", 0, PickerBitmap.TileTypes.CAMERA));
+
+        return pickerBitmaps;
+    }
+
+    /**
+     * @param filePath The file path to consider.
+     * @return true if the |filePath| ends in an image extension.
+     */
+    private boolean isImageExtension(String filePath) {
+        String file = filePath.toLowerCase(Locale.US);
+        return file.endsWith(".jpg") || file.endsWith(".gif") || file.endsWith(".png");

[Theresa, 2017/03/28 20:40:28]

This list should probably include ".webp" and ".bmp"

https://developer.android.com/guide/topics/media/media-formats.html#image-for...


I think relying on the extension is error prone, since files can be downloaded
from online with no extension or the incorrect extension. 

We should probably be relying on the mime type instead if possible.

[Finnur, 2017/03/31 14:26:49]

Acknowledged. Will change it in a future CL, since I'm removing this file
shortly (from this CL).

+    }
+
+    /**
+     * Communicates the results back to the client. Called on the UI thread.
+     * @param files The resulting list of files on disk.
+     */
+    @Override
+    protected void onPostExecute(List<PickerBitmap> files) {
+        if (isCancelled()) {
+            return;
+        }
+
+        mCallback.filesEnumeratedCallback(files);
+    }
+}