webapps: introduce helper class to store extended set of data

chrome/android/java/src/org/chromium/chrome/browser/webapps/WebappDataStorage.java

+// Copyright 2015 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.webapps;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+import android.graphics.Bitmap;
+import android.graphics.BitmapFactory;
+import android.os.AsyncTask;
+import android.text.TextUtils;
+import android.util.Base64;
+
+import java.io.ByteArrayOutputStream;
+
+/**
+ * This is a class used to store data about an installed webapp. It uses SharedPreferences
+ * to persist the data to disk.
+ */
+public class WebappDataStorage {
+
+    private static final String KEY_SPLASH_ICON = "splash_icon";
+    private static final String KEY_LAST_USED = "last_used";
+
+    private final SharedPreferences mPreferences;
+
+    /**
+     * Opens an instance of WebappDataStorage for the webapp specified.
+     * @param context  The context to open the SharedPreferences.
+     * @param webappId The ID of the webapp which is being opened.
+     */
+    public static WebappDataStorage open(Context context, String webappId) {
+        WebappDataStorage storage = new WebappDataStorage(
+                context.getApplicationContext(), webappId);
+        storage.updateLastAccessedTime();
+        return storage;
+    }
+
+    /**
+     * Retrieve the time which this WebappDataStorage was last opened using

[gone, 2015/08/26 21:56:14]

nit: Asynchronously retrieves the time which this WebappDataStorage was last
opened using {@link WebappDataStorage#open(Context, String)}.

[Lalit Maganti, 2015/08/26 22:33:53]

Done.

+     * {@link WebappDataStorage#open(Context, String)} asynchrously.
+     * @param context  The context to read the SharedPreferences file.
+     * @param webappId The ID of the webapp the accessed time is being read for.
+     * @param callback Called when the last accessed time has been retrieved.
+     */
+    public static WebappDataStorage getLastUsedTime(Context context, String webappId,
+            final FetchCallback<String> callback) {
+        return new WebappDataStorage(context.getApplicationContext(), webappId);
+    }
+
+    private WebappDataStorage(Context context, String webappId) {
+        mPreferences = context.getSharedPreferences("webapp_" + webappId,
+                Context.MODE_PRIVATE);
+    }
+
+    /*
+     * Retrieve the splash screen image associated with with the current webapp

[gone, 2015/08/26 21:56:14]

nit: Asynchronously retrieves the splash screen image associated with the
current webapp.

[Lalit Maganti, 2015/08/26 22:33:53]

Done.

+     * asynchrously.
+     * @param callback Called when the splash screen image has been retrieved.
+     *                 May be null if no image was found.
+     */
+    public void getSplashscreenImage(final FetchCallback<Bitmap> callback) {
+        new BitmapFetchTask(KEY_SPLASH_ICON, callback).execute();
+    }
+
+    /*
+     * Update the information associated with the webapp with the specified
+     * data.

[gone, 2015/08/26 21:56:14]

nit: wrap at 100.

[Lalit Maganti, 2015/08/26 22:33:54]

Done.

+     * @param splashscreenImage The image which should be shown on the splash screen of the webapp.
+     */
+    public void updateSplashscreenImage(final Bitmap splashscreenImage) {
+        new UpdateTask(splashscreenImage).execute();
+    }
+
+    private void getLastAccessedTime(final FetchCallback<String> callback) {
+        new AsyncTask<Void, Void, String>() {
+            @Override
+            protected final String doInBackground(Void... nothing) {
+                return mPreferences.getString(KEY_LAST_USED, null);
+            }
+
+            @Override
+            protected final void onPostExecute(String result) {
+                callback.run(result);
+            }
+        }.execute();
+    }
+
+    private WebappDataStorage updateLastAccessedTime() {
+        new AsyncTask<Void, Void, Void>() {
+            @Override
+            protected final Void doInBackground(Void... nothing) {
+                mPreferences.edit()
+                    .putLong(KEY_LAST_USED, System.currentTimeMillis())

[gone, 2015/08/26 21:56:14]

nit: indent by 8.

[Lalit Maganti, 2015/08/26 22:33:53]

Done.

+                    .commit();
+                return null;
+            }
+        }.execute();
+        return this;
+    }
+
+    /**
+     * Callback class used when items are requested from the storage.

[gone, 2015/08/26 21:56:14]

nit: Called after data has been retrieved from storage. 

[Lalit Maganti, 2015/08/26 22:33:53]

Done.

+     */
+    public interface FetchCallback<T> {
+        public void run(T readObject);

[gone, 2015/08/26 21:56:14]

run() -> onDataRetrieved().

[Lalit Maganti, 2015/08/26 22:33:54]

Done.

+    }
+
+    private final class BitmapFetchTask extends AsyncTask<Void, Void, Bitmap> {
+
+        private final String mKey;
+

[gone, 2015/08/26 21:56:14]

nit: remove newline?

[Lalit Maganti, 2015/08/26 22:33:54]

Done.

+        private final FetchCallback<Bitmap> mCallback;
+
+        public BitmapFetchTask(String key, FetchCallback<Bitmap> callback) {
+            mKey = key;
+            mCallback = callback;
+        }
+
+        @Override
+        protected final Bitmap doInBackground(Void... nothing) {
+            String icon = mPreferences.getString(mKey, null);
+            if (TextUtils.isEmpty(icon)) return null;
+
+            byte[] decoded = Base64.decode(icon, Base64.DEFAULT);
+            return BitmapFactory.decodeByteArray(decoded, 0, decoded.length);
+        }
+
+        @Override
+        protected final void onPostExecute(Bitmap result) {
+            mCallback.run(result);
+        }
+    }
+
+    private final class UpdateTask extends AsyncTask<Void, Void, Void> {
+
+        private final Bitmap mSplashImage;
+
+        public UpdateTask(Bitmap splashImage) {
+            mSplashImage = splashImage;
+        }
+
+        @Override
+        protected Void doInBackground(Void... nothing) {
+            ByteArrayOutputStream output = new ByteArrayOutputStream();
+            mSplashImage.compress(Bitmap.CompressFormat.PNG, 100, output);
+            String splashImageString = Base64.encodeToString(
+                    output.toByteArray(), Base64.DEFAULT);
+            mPreferences.edit()
+                .putString(KEY_SPLASH_ICON, splashImageString)

[Lalit Maganti, 2015/08/26 22:33:53]

Also indented at 8 to match above.

+                .commit();
+            return null;
+        }
+    }
+}