雑に gcmHelper.onCreate 呼ぶだけでよしなにやってくれるやつ。

GcmHelper.java

package co.kotori.grumbler.utils;

import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.os.AsyncTask;
import android.util.Log;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.gcm.GoogleCloudMessaging;

import java.io.IOException;

/**
 * Created by kaiinui on 2015/04/13.
 */
public class GcmHelper {
    public final int PLAY_SERVICES_RESOLUTION_REQUEST = 8773;
    public final String SHARED_PREFS_NAME = "co.kotori.utils.sharef_prefs";
    public final String PROPERTY_REG_ID = "co.kotori.utils.shared_prefs.reg_id";
    public final String PROPERTY_APP_VERSION = "co.kotori.utils.shared_prefs.app_version";
    private final String TAG = GcmHelper.class.getSimpleName();

    final Activity context;
    final String senderId;
    final RegistrationIdSender sender;
    GoogleCloudMessaging gcm;
    String regid;

    public GcmHelper(Activity context, String senderId, RegistrationIdSender sender) {
        this.context = context;
        this.senderId = senderId;
        this.sender = sender;
    }

    public interface RegistrationIdSender {
        boolean sendRegistrationIdToBackend(String registrationId);
    }

    public void onCreate() {
        if (checkPlayServices()) {
            gcm = GoogleCloudMessaging.getInstance(context);
            regid = getRegistrationId();

            if (regid.isEmpty()) {
                registerInBackground();
            } else {
                Log.i(TAG, "registrationID = " + regid);
            }
        } else {
            Log.i(TAG, "No valid Google Play Services APK found.");
        }
    }

    // Private Helpers

    private boolean checkPlayServices() {
        try {
            int resultCode = GooglePlayServicesUtil.isGooglePlayServicesAvailable(context);
            if (resultCode != ConnectionResult.SUCCESS) {
                if (GooglePlayServicesUtil.isUserRecoverableError(resultCode)) {
                    GooglePlayServicesUtil.getErrorDialog(resultCode, context, PLAY_SERVICES_RESOLUTION_REQUEST).show();
                }
                return false;
            }
        } catch (Exception e) {
            Log.d(TAG, e.toString());
        }
        return true;
    }


    private void registerInBackground() {
        new AsyncTask<Void, Void, String>() {
            @Override
            protected String doInBackground(Void... params) {
                String msg = "";
                try {
                    if (gcm == null) {
                        gcm = GoogleCloudMessaging.getInstance(context);
                    }
                    regid = gcm.register(senderId);
                    msg = "Device registered, registration ID=" + regid;

                    // 失敗したら保存しない。もう一度登録し直す。
                    if (sender.sendRegistrationIdToBackend(regid)) {
                        storeRegistrationId(regid);
                    } else {
                        Log.i(TAG, "Skipped saving regid due to send to backend failed.");
                    }
                } catch (IOException ex) {
                    msg = "Error :" + ex.getMessage();
                } catch (Throwable e) {
                    msg = "Error :" + e.getMessage();
                }
                return msg;
            }

            @Override
            protected void onPostExecute(String msg) {
                Log.i(TAG, msg + "\n");
            }
        }.execute(null, null, null);
    }

    // Shared Preferences

    /**
     * 現在のバージョンの regid を返します。もしバージョンが変わっていたり、前に登録されていなかったりすると "" が返ります。
     *
     * @return Current version's registration id. If not found, "" will be returned.
     */
    private String getRegistrationId() {
        final SharedPreferences prefs = getGCMPreferences();
        String registrationId = prefs.getString(PROPERTY_REG_ID, "");
        if (registrationId.isEmpty()) {
            Log.i(TAG, "Registration not found.");
            return "";
        }
        // Check if app was updated; if so, it must clear the registration ID
        // since the existing regID is not guaranteed to work with the new
        // app version.
        int registeredVersion = prefs.getInt(PROPERTY_APP_VERSION, Integer.MIN_VALUE);
        int currentVersion = getAppVersion();
        if (registeredVersion != currentVersion) {
            Log.i(TAG, "App version changed.");
            return "";
        }
        return registrationId;
    }

    private void storeRegistrationId(String regId) {
        final SharedPreferences prefs = getGCMPreferences();
        int appVersion = getAppVersion();
        Log.i(TAG, "Saving regId on app version " + appVersion);
        SharedPreferences.Editor editor = prefs.edit();
        editor.putString(PROPERTY_REG_ID, regId);
        editor.putInt(PROPERTY_APP_VERSION, appVersion);
        editor.commit();
    }

    private SharedPreferences getGCMPreferences() {
        return context.getSharedPreferences(SHARED_PREFS_NAME,
                Context.MODE_PRIVATE);
    }

    private int getAppVersion() {
        try {
            final PackageInfo packageInfo = context.getPackageManager().getPackageInfo(context.getPackageName(), 0);
            return packageInfo.versionCode;
        } catch (PackageManager.NameNotFoundException e) {
            throw new RuntimeException("Could not get package name: " + e);
        }
    }
}