android - Attempt to invoke virtual method 'void com.facebook.login.widget.LoginButton.setReadPermissions(java.lang.String[])' on a null object reference

I tried to make a Facebook connection, but it seems I made a mistake, and now my Facebook button crashes.

public class FacebookConnect extends AppCompatActivity {

    private CallbackManager callbackManager;
    private AccessTokenTracker accessTokenTracker;

    private ProfileTracker profileTracker;
    public String TAG;


    private FacebookCallback callback = new FacebookCallback() {
        @Override
        public void onSuccess(LoginResult loginResult) {
            Profile profile = Profile.getCurrentProfile();
            nextActivity(profile);
        }


        @Override
        public void onCancel() {

        }

        @Override
        public void onError(FacebookException error) {
            System.out.println("test");
        }

    };

    @Override
    public void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        callbackManager = CallbackManager.Factory.create();
        accessTokenTracker = new AccessTokenTracker() {
            @Override
            protected void onCurrentAccessTokenChanged(AccessToken oldAccessToken,
                                                       AccessToken currentAccessToken) {

            }
        };
        profileTracker = new ProfileTracker() {
            @Override
            protected void onCurrentProfileChanged(Profile oldProfile, Profile currentProfile) {
                nextActivity(currentProfile);
            }
        };
        accessTokenTracker.startTracking();
        profileTracker.startTracking();

        LoginButton loginButton = (LoginButton)findViewById(R.id.facebookSignupButton);
        loginButton.setReadPermissions("user_friends");
        loginButton.registerCallback(callbackManager, callback);
        new FacebookCallback() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                Profile profile = Profile.getCurrentProfile();
                nextActivity(profile);
                Toast.makeText(getApplicationContext(), "Log in", Toast.LENGTH_SHORT).show();
            }


            @Override
            public void onCancel() {

            }

            @Override
            public void onError(FacebookException error) {

            }

        };
    }
    @Override
    protected void onResume(){
        super.onResume();
        Profile profile = Profile.getCurrentProfile();
        nextActivity(profile);
    }

    protected void onPause(){

        super.onPause();
    }

    protected void onStop(){
        super.onStop();
        accessTokenTracker.stopTracking();
        profileTracker.stopTracking();
    }

    @Override

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

    private void nextActivity(Profile profile){
        if (profile != null){
            Intent main = new Intent(this, NavigationActivity.class);
            main.putExtra("name", profile.getFirstName());
            main.putExtra("surname", profile.getLastName());

            main.putExtra("imageUrl", profile.getProfilePictureUri(200,200).toString());
            Log.d(TAG, "Connected");
            startActivity(main);
        }
    }
}

Do you know how to solve it ?

This is actually the error when I clicked on, I have the same problem when I tried make a google connection too.

12-07 19:54:48.717 3772-3772/com.climb.eip.climb E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.climb.eip.climb, PID: 3772
java.lang.RuntimeException: Unable to start activity
ComponentInfo{com.climb.eip.climb/com.climb.eip.climb.utils.FacebookConnect}:
java.lang.NullPointerException: Attempt to invoke virtual method 'void
com.facebook.login.widget.LoginButton.setReadPermissions(java.lang.String[])'
on a null object reference

at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2646)
at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707)
at android.app.ActivityThread.-wrap12(ActivityThread.java)
at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6077)

at java.lang.reflect.Method.invoke(Native Method)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual
method 'void
com.facebook.login.widget.LoginButton.setReadPermissions(java.lang.String[])'
on a null object reference
at
com.climb.eip.climb.utils.FacebookConnect.onCreate(FacebookConnect.java:76)

at android.app.Activity.performCreate(Activity.java:6662)
at
android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118)
at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2599)
at
android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2707) 
at android.app.ActivityThread.-wrap12(ActivityThread.java) 
at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1460) 

at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:154) 
at android.app.ActivityThread.main(ActivityThread.java:6077) 
at java.lang.reflect.Method.invoke(Native Method) 
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)