Question

我正在尝试使用this教程在我的应用中通过gcm实现推送通知我成功地能够注册我的设备，但我得到了空指针异常注册完成后，onMessage（）。

Logcat：

04-21 15:03:11.450: E/AndroidRuntime(8406): FATAL EXCEPTION: IntentService[GCMIntentService-495933236312-2]
04-21 15:03:11.450: E/AndroidRuntime(8406): java.lang.NullPointerException
04-21 15:03:11.450: E/AndroidRuntime(8406):     at com.ht.mobilecop.GCMIntentService.onMessage(GCMIntentService.java:65)
04-21 15:03:11.450: E/AndroidRuntime(8406):     at com.google.android.gcm.GCMBaseIntentService.onHandleIntent(GCMBaseIntentService.java:223)
04-21 15:03:11.450: E/AndroidRuntime(8406):     at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
04-21 15:03:11.450: E/AndroidRuntime(8406):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-21 15:03:11.450: E/AndroidRuntime(8406):     at android.os.Looper.loop(Looper.java:137)
04-21 15:03:11.450: E/AndroidRuntime(8406):     at android.os.HandlerThread.run(HandlerThread.java:60)

createAccount part：

            if (regId.equals("")) {
                // Registration is not present, register now with GCM           
                GCMRegistrar.register(this, SENDER_ID);
            } else {
                // Device is already registered on GCM
//              if (GCMRegistrar.isRegisteredOnServer(this)) {
//                  // Skips registration.              
//                  Toast.makeText(getApplicationContext(), "Already registered with GCM", Toast.LENGTH_LONG).show();
//              } else {
                    // Try to register again, but not in the UI thread.
                    // It's also necessary to cancel the thread onDestroy(),
                    // hence the use of AsyncTask instead of a raw thread.
                    final Context context = this;
                    mRegisterTask = new AsyncTask<Void, Void, Void>() {

                        @Override
                        protected Void doInBackground(Void... params) {
                            // Register on our server
                            // On server creates a new user
                            name = et_user_name.getText().toString();
                            email = et_email.getText().toString() ;

                            ServerUtilities.register(context, name,  email, regId);

                            return null;
                        }

                        @Override
                        protected void onPostExecute(Void result) {
                            mRegisterTask = null;
                            editor = getSharedPreferences("account_status", 0).edit();
                            editor.putString("result", Constants.KEY_SUCCESS);

                            editor.commit();

                            Intent i = new Intent(CreateAccountActivity.this , TabHostActivity.class);
                            i.putExtra("name", et_user_name.getText().toString());
                            i.putExtra("email", et_email.getText().toString());
                            startActivity(i);
                            finish();
                        }

                    };
                    mRegisterTask.execute(null, null, null);
                //}
            }

GCMIntentService：

public class GCMIntentService extends GCMBaseIntentService {

    private static final String TAG = "GCMIntentService";
    private static final String CAMERA_REQUEST = null;



    public GCMIntentService() {
        super(SENDER_ID);
    }

    /**
     * Method called on device registered
     **/
    @Override
    protected void onRegistered(Context context, String registrationId) {
        Log.i(TAG, "Device registered: regId = " + registrationId);

        ServerUtilities.register(context, CreateAccountActivity.name, CreateAccountActivity.email, registrationId);
    }

    /**
     * Method called on device un registred
     * */
    @Override
    protected void onUnregistered(Context context, String registrationId) {
        Log.i(TAG, "Device unregistered");
        displayMessage(context, getString(R.string.gcm_unregistered));
        ServerUtilities.unregister(context, registrationId);
    }

    /**
     * Method called on Receiving a new message
     * */
    @Override
    protected void onMessage(Context context, Intent intent) {
        Log.i(TAG, "Received message");
        String message = intent.getExtras().getString("alert");

        displayMessage(context, message); 
        if(message.equals("login"))
        {
            showAlert(context); // for testing
        }

        // notifies user
        generateNotification(context, message);
    }

    /**
     * Method called on receiving a deleted message
     * */
    @Override
    protected void onDeletedMessages(Context context, int total) {
        Log.i(TAG, "Received deleted messages notification");
        String message = getString(R.string.gcm_deleted, total);
        displayMessage(context, message);
        // notifies user
        generateNotification(context, message);
    }

    /**
     * Method called on Error
     * */
    @Override
    public void onError(Context context, String errorId) {
        Log.i(TAG, "Received error: " + errorId);
        displayMessage(context, getString(R.string.gcm_error, errorId));
    }

    @Override
    protected boolean onRecoverableError(Context context, String errorId) {
        // log message
        Log.i(TAG, "Received recoverable error: " + errorId);
        displayMessage(context, getString(R.string.gcm_recoverable_error,
                errorId));
        return super.onRecoverableError(context, errorId);
    }

    /**
     * Issues a notification to inform the user that server has sent a message.
     */
    private static void generateNotification(Context context, String message) {
        int icon = R.drawable.ic_launcher;
        long when = System.currentTimeMillis();
        NotificationManager notificationManager = (NotificationManager)
                context.getSystemService(Context.NOTIFICATION_SERVICE);
        Notification notification = new Notification(icon, message, when);

        String title = context.getString(R.string.app_name);

        Intent notificationIntent = new Intent(context, LoginActivity.class);
        // set intent so it does not start a new activity
        notificationIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP |
                Intent.FLAG_ACTIVITY_SINGLE_TOP);
        PendingIntent intent =
                PendingIntent.getActivity(context, 0, notificationIntent, 0);
        notification.setLatestEventInfo(context, title, message, intent);
        notification.flags |= Notification.FLAG_AUTO_CANCEL;

        // Play default notification sound
        notification.defaults |= Notification.DEFAULT_SOUND;

        //notification.sound = Uri.parse("android.resource://" + context.getPackageName() + "your_sound_file_name.mp3");

        // Vibrate if vibrate is enabled
        notification.defaults |= Notification.DEFAULT_VIBRATE;
        notificationManager.notify(0, notification);      

    }

Answer 1

将GCMIntentService类放入主程序包而不是其他程序包，并在清单文件中注册，例如，在放置代码后，清单如下所示：

    ...
    <uses-permission android:name="android.permission.VIBRATE"/>
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="YOUR_PACKAGE_NAME_HERE.permission.C2D_MESSAGE" />
    <uses-permission android:name="android.permission.GET_ACCOUNTS" />
    <uses-permission android:name="android.permission.WAKE_LOCK" />
    <uses-permission android:name="com.google.android.c2dm.permission.RECEIVE" />

    <permission
        android:name="YOUR_PACKAGE_NAME_HERE.permission.C2D_MESSAGE"
        android:protectionLevel="signature" />

<receiver
            android:name="com.google.android.gcm.GCMBroadcastReceiver"
            android:permission="com.google.android.c2dm.permission.SEND" >
            <intent-filter>
                <action android:name="com.google.android.c2dm.intent.RECEIVE" />
                <action android:name="com.google.android.c2dm.intent.REGISTRATION" />

                <category android:name="YOUR_PACKAGE_NAME_HERE" />
            </intent-filter>
        </receiver>

       <service android:name=".GCMIntentService" />
    </application>

Answer 2

您真的需要阅读How to check if my string is equal to null?

要解决您的问题，您需要执行

if(message == null) {

}

OR，Android给TextUtils.isEmpty()检查字符串是否为null或为空。

if(TextUtils.isEmpty(message)) {
   // Handle null string
}

而不是

if(message.equals(null)|| message.equals("")) // Nullpointer at this line
        {

        }

java.lang.NullPointerException：GCMIntentService.onMessage

2 个答案: