HelpUtils.java

/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.fastergallery.util;

import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;

import java.util.Locale;

/**
 * Functions to easily prepare contextual help menu option items with an intent
 * that opens up the browser to a particular URL, while taking into account the
 * preferred language and app version.
 */
public class HelpUtils {
	private final static String TAG = HelpUtils.class.getName();

	/**
	 * Help URL query parameter key for the preferred language.
	 */
	private final static String PARAM_LANGUAGE_CODE = "hl";

	/**
	 * Help URL query parameter key for the app version.
	 */
	private final static String PARAM_VERSION = "version";

	/**
	 * Cached version code to prevent repeated calls to the package manager.
	 */
	private static String sCachedVersionCode = null;

	/** Static helper that is not instantiable */
	private HelpUtils() {
	}

	public static Intent getHelpIntent(Context context, int helpUrlResId) {
		String helpUrlString = context.getString(helpUrlResId);

		if (TextUtils.isEmpty(helpUrlString)) {
			return null;
		} else {
			// The help url string exists, so first add in some extra query
			// parameters.
			final Uri fullUri = uriWithAddedParameters(context,
					Uri.parse(helpUrlString));

			// Then, create an intent that will be fired when the user
			// selects this help menu item.
			Intent intent = new Intent(Intent.ACTION_VIEW, fullUri);
			intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK
					| Intent.FLAG_ACTIVITY_EXCLUDE_FROM_RECENTS);
			return intent;
		}
	}

	/**
	 * Adds two query parameters into the Uri, namely the language code and the
	 * version code of the app's package as gotten via the context.
	 * 
	 * @return the uri with added query parameters
	 */
	private static Uri uriWithAddedParameters(Context context, Uri baseUri) {
		Uri.Builder builder = baseUri.buildUpon();

		// Add in the preferred language
		builder.appendQueryParameter(PARAM_LANGUAGE_CODE, Locale.getDefault()
				.toString());

		// Add in the package version code
		if (sCachedVersionCode == null) {
			// There is no cached version code, so try to get it from the
			// package manager.
			try {
				// cache the version code
				PackageInfo info = context.getPackageManager().getPackageInfo(
						context.getPackageName(), 0);
				sCachedVersionCode = Integer.toString(info.versionCode);

				// append the version code to the uri
				builder.appendQueryParameter(PARAM_VERSION, sCachedVersionCode);
			} catch (NameNotFoundException e) {
				// Cannot find the package name, so don't add in the version
				// parameter
				// This shouldn't happen.
				Log.wtf(TAG, "Invalid package name for context", e);
			}
		} else {
			builder.appendQueryParameter(PARAM_VERSION, sCachedVersionCode);
		}

		// Build the full uri and return it
		return builder.build();
	}
}