Implement the new Photo picker, part two.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/photo_picker/FileEnumWorkerTask.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/FileEnumWorkerTask.java b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/FileEnumWorkerTask.java
new file mode 100644
index 0000000000000000000000000000000000000000..713d7eb4e77c16b36be08184ac0d26481872bd28
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/photo_picker/FileEnumWorkerTask.java
@@ -0,0 +1,110 @@
+// Copyright 2016 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 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 AcceptFileFilter mFilter;
+
+    /**
+     * A FileEnumWorkerTask constructor.
+     * @param callback The callback to use to communicate back the results.
+     */
+    public FileEnumWorkerTask(FilesEnumeratedCallback callback) {
+        this(callback, AcceptFileFilter.getDefault());
+    }
+
+    /**
+     * 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, AcceptFileFilter filter) {
+        mCallback = callback;
+        mFilter = filter;
+    }
+
+    /**
+     * 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) {
+        if (isCancelled()) {
+            return null;
+        }
+
+        List<PickerBitmap> pickerBitmaps = new ArrayList<>();
+
+        String paths[] = new String[3];
+        paths[0] = "/DCIM/Camera";
+        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;
+                }
+
+                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;
+    }
+
+    /**
+     * 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);
+    }
+}