Eula.java

/* Copyright (c) 2009 Miltiadis Allamanis
 * 
 * The MIT License
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package app.randgen;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.content.SharedPreferences;
import app.randgen.R;

import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.Closeable;

/**
 * Displays an EULA ("End User License Agreement") that the user has to accept
 * before using the application. Your application should call
 * {@link Eula#show(android.app.Activity)} in the onCreate() method of the first
 * activity. If the user accepts the EULA, it will never be shown again. If the
 * user refuses, {@link android.app.Activity#finish()} is invoked on your
 * activity.
 */
class Eula {
	private static final String ASSET_EULA = "EULA";
	private static final String PREFERENCE_EULA_ACCEPTED = "eula.accepted";
	private static final String PREFERENCES_EULA = "eula";

	/**
	 * callback to let the activity know when the user has accepted the EULA.
	 */
	static interface OnEulaAgreedTo {

		/**
		 * Called when the user has accepted the eula and the dialog closes.
		 */
		void onEulaAgreedTo();
	}

	/**
	 * Displays the EULA if necessary. This method should be called from the
	 * onCreate() method of your main Activity.
	 * 
	 * @param activity
	 *            The Activity to finish if the user rejects the EULA.
	 * @return Whether the user has agreed already.
	 */
	static boolean show(final Activity activity) {
		final SharedPreferences preferences = activity.getSharedPreferences(
				PREFERENCES_EULA, Activity.MODE_PRIVATE);
		if (!preferences.getBoolean(PREFERENCE_EULA_ACCEPTED, false)) {
			final AlertDialog.Builder builder = new AlertDialog.Builder(
					activity);
			builder.setTitle(R.string.eula_title);
			builder.setCancelable(true);
			builder.setPositiveButton(R.string.eula_accept,
					new DialogInterface.OnClickListener() {
						public void onClick(DialogInterface dialog, int which) {
							accept(preferences);
							if (activity instanceof OnEulaAgreedTo) {
								((OnEulaAgreedTo) activity).onEulaAgreedTo();
							}
						}
					});
			builder.setNegativeButton(R.string.eula_refuse,
					new DialogInterface.OnClickListener() {
						public void onClick(DialogInterface dialog, int which) {
							refuse(activity);
						}
					});
			builder.setOnCancelListener(new DialogInterface.OnCancelListener() {
				public void onCancel(DialogInterface dialog) {
					refuse(activity);
				}
			});
			builder.setMessage(readEula(activity));
			builder.create().show();
			return false;
		}
		return true;
	}

	private static void accept(SharedPreferences preferences) {
		preferences.edit().putBoolean(PREFERENCE_EULA_ACCEPTED, true).commit();
	}

	private static void refuse(Activity activity) {
		activity.finish();
	}

	private static CharSequence readEula(Activity activity) {
		BufferedReader in = null;
		try {
			in = new BufferedReader(new InputStreamReader(activity.getAssets()
					.open(ASSET_EULA)));
			String line;
			StringBuilder buffer = new StringBuilder();
			while ((line = in.readLine()) != null)
				buffer.append(line).append('\n');
			return buffer;
		} catch (IOException e) {
			return "";
		} finally {
			closeStream(in);
		}
	}

	/**
	 * Closes the specified stream.
	 * 
	 * @param stream
	 *            The stream to close.
	 */
	private static void closeStream(Closeable stream) {
		if (stream != null) {
			try {
				stream.close();
			} catch (IOException e) {
				// Ignore
			}
		}
	}
}