android - 解析 + Facebook 認証: コールバックは既に登録されています: com.parse.ParseFacebookUtils

Question

アプリケーションで Parse を介して Facebook 認証を追加する必要があります。https://parse.com/docs/android/guide#users-facebook-usersの指示に従います。しかし、アプリを実行し、[戻る] ボタンを押してからもう一度実行すると、常に次のエラーが発生します。

java.lang.RuntimeException: Unable to start activity ComponentInfo{.AuthActivity}: java.lang.IllegalStateException: Callback already registered for <facebook>: com.parse.ParseFacebookUtils$1@28d04f8f
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2693)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758)
    at android.app.ActivityThread.access$900(ActivityThread.java:177)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:145)
    at android.app.ActivityThread.main(ActivityThread.java:5942)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195)
 Caused by: java.lang.IllegalStateException: Callback already registered for <facebook>: com.parse.ParseFacebookUtils$1@28d04f8f
    at com.parse.ParseAuthenticationManager.register(ParseAuthenticationManager.java:35)
    at com.parse.ParseUser.registerAuthenticationCallback(ParseUser.java:1094)
    at com.parse.ParseFacebookUtils$ParseUserDelegateImpl.registerAuthenticationCallback(ParseFacebookUtils.java:562)
    at com.parse.ParseFacebookUtils.initialize(ParseFacebookUtils.java:109)
    at com.parse.ParseFacebookUtils.initialize(ParseFacebookUtils.java:92)
    at .AuthActivity.onCreate(AuthActivity.java:47)
    at android.app.Activity.performCreate(Activity.java:6289)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2758) 
    at android.app.ActivityThread.access$900(ActivityThread.java:177) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1448) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:145) 
    at android.app.ActivityThread.main(ActivityThread.java:5942) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1400) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1195) 

それが私のアクティビティがどのように見えるかです:

public class AuthActivity extends AppCompatActivity {
    …

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ParseFacebookUtils.initialize(this); // crash here

        setupEvents();

        …
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        ParseFacebookUtils.onActivityResult(requestCode, resultCode, data);
    }

    private void setupEvents() {
        findViewById(R.id.fb_login).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                loginViaFacebook();
            }
        });
    }

    private void loginViaFacebook() {
        ParseFacebookUtils.logInWithReadPermissionsInBackground(AuthActivity.this, null, new LogInCallback() {
            @Override
            public void done(ParseUser user, ParseException err) {
                …
            }
        });
    }
}

ここで何が問題なのですか？