具有Facebook登录名的Android应用：该应用仅在授予权限并崩溃后才能运行

Question

When the app starts for the first time and the user grants permission, the app crashes. If the app is restarted the user is already logged in and the app works perfectly.

To recreate the error I have to delete the app from the phone and disassociate the app from my Facebook account. ( if this helps )

Also to clarify, I understand what a null pointer exception is, just don't quite understand why it is happening on only the first run. Do I need to add some kind of statement for the first time run?

            @Override
        protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    FacebookSdk.sdkInitialize(getApplicationContext());
    Parse.enableLocalDatastore(this);
    Parse.initialize(this);
    //parse test
    ParseObject testObject = new ParseObject("TestObject");
    testObject.put("foo", "bar");
    testObject.saveInBackground();

    callbackManager = CallbackManager.Factory.create();

    setContentView(R.layout.activity_main_page);
    info = (TextView) findViewById(R.id.info);
    loginButton = (LoginButton) findViewById(R.id.login_button);

    Bundle logout_req = getIntent().getExtras();
    if (logout_req != null) {
        String logout = logout_req.getString("user_logout");
        if (logout == "logout") {
            LoginManager.getInstance().logOut();
        }
    }

    Toolbar myToolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(myToolbar);


    if (Profile.getCurrentProfile() != null) {
        Profile profile1 = Profile.getCurrentProfile();
        Intent myIntent = new Intent(getBaseContext(), Home.class);
        myIntent.putExtra("user_id", profile1.getId());
        myIntent.putExtra("user_name", profile1.getName());
        MainPage.this.startActivity(myIntent);
    }


            loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {

                Profile profile = Profile.getCurrentProfile();
                ParseUser.logInInBackground(profile.getId(), "0", new LogInCallback() {
                    public void done(ParseUser user, ParseException e) {
                        if (user == null) {

                            //No such user, create a new user.
                            ParseUser newUser = new ParseUser();

                            Profile profile = Profile.getCurrentProfile();
                            newUser.setUsername(profile.getId());
                            newUser.setPassword("0");
                            newUser.signUpInBackground();

                            //Send required data to home page
                            Intent myIntent = new Intent(getBaseContext(), Home.class);
                            myIntent.putExtra("user_id", profile.getId());
                            myIntent.putExtra("user_name", profile.getName());
                            MainPage.this.startActivity(myIntent);
                            System.out.println("NEW USER CREATED! LOGGED IN AND SENT TO HOMEPAGE");


                        } else {

                            Profile profile = Profile.getCurrentProfile();
                            //Send required data to home page
                            Intent myIntent = new Intent(getBaseContext(), Home.class);
                            myIntent.putExtra("user_id", profile.getId());
                            myIntent.putExtra("user_name", profile.getName());
                            MainPage.this.startActivity(myIntent);
                            System.out.println("USER LOGGED IN! SENT TO HOMEPAGE");
                        }
                    }
                });
            }

            @Override
            public void onCancel() {
                info.setText("Login attempt canceled    .");
            }

            @Override
            public void onError(FacebookException e) {

                info.setText("Login attempt failed.");
            }
        });
    }

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

The error appears to happen just after loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>()

The error:

Process: com.george.coffeeconversation, PID: 16920
  java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=64206, result=-1, data=Intent { (has extras) }} to activity {com.george.coffeeconversation/com.george.coffeeconversation.MainPage}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.facebook.Profile.getId()' on a null object reference
  at android.app.ActivityThread.deliverResults(ActivityThread.java:3680)
  at android.app.ActivityThread.handleSendResult(ActivityThread.java:3723)
  at android.app.ActivityThread.access$1300(ActivityThread.java:156)
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1400)
  at android.os.Handler.dispatchMessage(Handler.java:102)
  at android.os.Looper.loop(Looper.java:211)
  at android.app.ActivityThread.main(ActivityThread.java:5373)
  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:1020)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815)
  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.facebook.Profile.getId()' on a null object reference
  at com.george.coffeeconversation.MainPage.run(MainPage.java:108)
  at com.george.coffeeconversation.MainPage$1.onSuccess(MainPage.java:90)
  at com.george.coffeeconversation.MainPage$1.onSuccess(MainPage.java:87)
  at com.facebook.login.LoginManager.finishLogin(LoginManager.java:510)
  at com.facebook.login.LoginManager.onActivityResult(LoginManager.java:193)
  at com.facebook.login.LoginManager$1.onActivityResult(LoginManager.java:136)
  at com.facebook.internal.CallbackManagerImpl.onActivityResult(CallbackManagerImpl.java:82)
  at com.george.coffeeconversation.MainPage.onActivityResult(MainPage.java:144)
  at android.app.Activity.dispatchActivityResult(Activity.java:6192)
  at android.app.ActivityThread.deliverResults(ActivityThread.java:3676)
  at android.app.ActivityThread.handleSendResult(ActivityThread.java:3723) 
  at android.app.ActivityThread.access$1300(ActivityThread.java:156) 
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1400) 
  at android.os.Handler.dispatchMessage(Handler.java:102) 
  at android.os.Looper.loop(Looper.java:211) 
  at android.app.ActivityThread.main(ActivityThread.java:5373) 
  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:1020) 
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:815) 

Answer 1

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.facebook.Profile.getId()' on a null object reference

Apparently the Profile object you're trying to access is null at the point in time you're referencing it.

Since you mentioned it's occurring after returning from Facebook, it's probably happening in either done(ParseUser user, ParseException e) or onSuccess(LoginResult loginResult) .

Try logging whether Profile.getCurrentProfile() is null at those points and you'll be able to track it down.