GCMUtils.java

package ca.grocerygo.android.gcm;

import android.content.Context;
import android.content.SharedPreferences;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.util.Log;
import ca.grocerygo.android.GroceryApplication;

import java.sql.Timestamp;

/**
 * User: robert
 * Date: 21/06/13
 */
public class GCMUtils {
    public static final String SENDER_ID = "554701520307";

    public static final String PROPERTY_REG_ID = "registration_id";
    private static final String PROPERTY_APP_VERSION = "appVersion";
    private static final String PROPERTY_ON_SERVER_EXPIRATION_TIME =
            "onServerExpirationTimeMs";

    //    Default lifespan (7 days) of a reservation until it is considered expired.
    public static final long REGISTRATION_EXPIRY_TIME_MS = 1000 * 3600 * 24 * 7;

    public static String getRegistrationId(Context context) {
        final SharedPreferences prefs = getGCMPreferences(context);
        String registrationId = prefs.getString(PROPERTY_REG_ID, "");
        if (registrationId.length() == 0) {
            Log.i(GroceryApplication.TAG, "Registration not found.");
            return "";
        }
        // check if app was updated; if so, it must clear registration id to
        // avoid a race condition if GCM sends a message
        int registeredVersion = prefs.getInt(PROPERTY_APP_VERSION, Integer.MIN_VALUE);
        int currentVersion = getAppVersion(context);
        if (registeredVersion != currentVersion || isRegistrationExpired(context)) {
            Log.i(GroceryApplication.TAG, "App version changed or registration expired.");
            return "";
        }
        return registrationId;
    }

    public static void setRegistrationId(Context context, String regId) {
        final SharedPreferences prefs = getGCMPreferences(context);
        int appVersion = getAppVersion(context);
        Log.i(GroceryApplication.TAG, "Saving regId on app version " + appVersion);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putString(PROPERTY_REG_ID, regId);
        editor.putInt(PROPERTY_APP_VERSION, appVersion);
        long expirationTime = System.currentTimeMillis() + REGISTRATION_EXPIRY_TIME_MS;

        Log.i(GroceryApplication.TAG, "Setting registration expiry time to " +
                new Timestamp(expirationTime));
        editor.putLong(PROPERTY_ON_SERVER_EXPIRATION_TIME, expirationTime);
        editor.commit();
    }

    private static SharedPreferences getGCMPreferences(Context context) {
        return context.getSharedPreferences(GCMUtils.class.getSimpleName(), Context.MODE_PRIVATE);
    }

    private static int getAppVersion(Context context) {
        try {
            PackageInfo packageInfo = context.getPackageManager()
                    .getPackageInfo(context.getPackageName(), 0);
            return packageInfo.versionCode;
        } catch (PackageManager.NameNotFoundException e) {
            // should never happen
            throw new RuntimeException("Could not get package name: " + e);
        }
    }

    private static boolean isRegistrationExpired(Context context) {
        final SharedPreferences prefs = getGCMPreferences(context);
        // checks if the information is not stale
        long expirationTime =
                prefs.getLong(PROPERTY_ON_SERVER_EXPIRATION_TIME, -1);
        return System.currentTimeMillis() > expirationTime;
    }
}