Photo Picker Dialog: Recursively traverse the photo directories.

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

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// 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 org.chromium.base.ThreadUtils;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * 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;
+
+    // The camera directory undir DCIM.
+    private static final String SAMPLE_DCIM_SOURCE_SUB_DIRECTORY = "Camera";
+
+    /**
+     * 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;
+    }
+
+    /**
+     * Retrieves the DCIM/camera directory.
+     */
+    private File getCameraDirectory() {
+        return new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DCIM),
+                SAMPLE_DCIM_SOURCE_SUB_DIRECTORY);
+    }
+
+    /**
+     * Recursively enumerate files in a directory (and subdirectories) and add them to a list.
+     * @param directory The parent directory to recursively traverse.
+     * @param pickerBitmaps The list to add the results to.
+     * @return True if traversing can continue, false if traversing was aborted and should stop.
+     */
+    private boolean traverseDir(File directory, List<PickerBitmap> pickerBitmaps) {
+        File[] files = directory.listFiles(mFilter);
+        if (files == null) {
+            return true;

[Theresa, 2017/04/10 18:01:14]

nit: inline this

if (files == null) return true;

[Finnur, 2017/04/11 11:30:57]

Done.

+        }
+
+        for (File file : files) {
+            if (isCancelled()) {
+                return false;
+            }
+
+            if (file.isDirectory()) {
+                return traverseDir(file, pickerBitmaps);
+            }
+
+            pickerBitmaps.add(
+                    new PickerBitmap(file.getPath(), file.lastModified(), PickerBitmap.PICTURE));
+        }
+
+        return true;
+    }
+
+    /**
+     * Enumerates (in the background) the image files on disk. Called on a non-UI thread
+     * @param params Ignored, do not use.
+     * @return A sorted list of images (by last-modified first).
+     */
+    @Override
+    protected List<PickerBitmap> doInBackground(Void... params) {
+        assert !ThreadUtils.runningOnUiThread();
+
+        if (isCancelled()) return null;
+
+        List<PickerBitmap> pickerBitmaps = new ArrayList<>();
+
+        File[] sourceDirs = new File[] {
+                getCameraDirectory(),
+                Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
+                Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS),

[Theresa, 2017/04/10 18:01:14]

If videos/* is an accepted type, should we also be checking DIRECTORY_MOVIES?
What about DIRECTORY_DOCUMENTS? Or the screenshots directory?

It may be safest just to check all directories in the public directory. In
Android's photo picker, I see standard folders as well as custom ones (e.g.
"image_search").

[Finnur, 2017/04/11 11:30:57]

videos/* I'll remove, because we don't have good thumbnails for those -- at
least not yet.

But I'm very hesitant to add the top level folder, not just because it will slow
enumeration down, but also because, at least on my phone, there's the
high-quality photos but also a *lot* of junk images I don't really care about:
downloads, screenshots and images from other apps. I'll start a thread on this,
though.

[Theresa, 2017/04/11 15:44:48]

I think screenshots are really important e.g. screenshots of text message
threads are often posted online. Thanks for starting the thread -- we can iron
out the policy there.

+        };
+
+        for (File directory : sourceDirs) {
+            if (!traverseDir(directory, pickerBitmaps)) return null;
+        }
+
+        Collections.sort(pickerBitmaps);
+
+        pickerBitmaps.add(0, new PickerBitmap("", 0, PickerBitmap.GALLERY));
+        pickerBitmaps.add(0, new PickerBitmap("", 0, PickerBitmap.CAMERA));
+
+        return pickerBitmaps;
+    }
+
+    /**
+     * 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);
+    }
+}