Java Android-Facebook SDK登录->；注销->；登录不工作

我有一个Android应用程序（非常简单，刚刚开始学习基础知识）。我已经实现了Facebook登录，它几乎可以完美地工作。第一次启动应用程序时一切正常：按下登录按钮，请求权限，登录，然后应用程序为用户显示经过身份验证的页面。当按下注销按钮时，它会再次显示登录页面，这样也能正常工作。现在，当我再次尝试登录时，它不起作用。它会再次打开facebook的内容几秒钟，然后返回登录页面，就像什么都没发生一样。如果我删除facebook上该应用程序的权限并再次尝试登录，它将再次工作。因此，由于某种原因，我无法登录，当我已经有了权限，我猜

代码如下：

package com.just.simply.myapplication;

import android.content.Intent;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.view.Menu;
import android.view.MenuItem;

import com.facebook.Session;
import com.facebook.SessionState;
import com.facebook.UiLifecycleHelper;

public class MyActivity extends FragmentActivity {

    private static final int SPLASH = 0;
    private static final int SELECTION = 1;
    private static final int SETTINGS = 2;
    private static final int FRAGMENT_COUNT = SETTINGS + 1;

    private Fragment[] fragments = new Fragment[FRAGMENT_COUNT];

    private boolean isResumed = false;
    private MenuItem settings;

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

        uiHelper = new UiLifecycleHelper(this, callback);
        uiHelper.onCreate(savedInstanceState);

        setContentView(R.layout.activity_my);

        FragmentManager fm = getSupportFragmentManager();
        fragments[SPLASH] = fm.findFragmentById(R.id.splashFragment);
        fragments[SELECTION] = fm.findFragmentById(R.id.selectionFragment);
        fragments[SETTINGS] = fm.findFragmentById(R.id.userSettingsFragment);

        FragmentTransaction transaction = fm.beginTransaction();
        for(int i = 0; i < fragments.length; i++) {
            transaction.hide(fragments[i]);
        }
        transaction.commit();
    }

    @Override
    public void onResume() {
        super.onResume();
        uiHelper.onResume();
        isResumed = true;
    }

    @Override
    public void onPause() {
        super.onPause();
        uiHelper.onPause();
        isResumed = false;
    }

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

    @Override
    public void onDestroy() {
        super.onDestroy();
        uiHelper.onDestroy();
    }

    @Override
    protected void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
        uiHelper.onSaveInstanceState(outState);
    }

    private void onSessionStateChange(Session session, SessionState state, Exception exception) {
        // Only make changes if the activity is visible
        if (isResumed) {
            FragmentManager manager = getSupportFragmentManager();
            // Get the number of entries in the back stack
            int backStackSize = manager.getBackStackEntryCount();
            // Clear the back stack
            for (int i = 0; i < backStackSize; i++) {
                manager.popBackStack();
            }
            if (state.isOpened()) {
                // If the session state is open:
                // Show the authenticated fragment
                showFragment(SELECTION, false);
            } else if (state.isClosed()) {
                // If the session state is closed:
                // Show the login fragment
                showFragment(SPLASH, false);
            }
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.equals(settings)) {
            showFragment(SETTINGS, true);
            return true;
        }
        return false;
    }

    @Override
    protected void onResumeFragments() {
        super.onResumeFragments();
        Session session = Session.getActiveSession();

        if (session != null && session.isOpened()) {
            // if the session is already open,
            // try to show the selection fragment
            showFragment(SELECTION, false);
        } else {
            // otherwise present the splash screen
            // and ask the person to login.
            showFragment(SPLASH, false);
        }
    }

    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        // only add the menu when the selection fragment is showing
        if (fragments[SELECTION].isVisible()) {
            if (menu.size() == 0) {
                settings = menu.add(R.string.settings);
            }
            return true;
        } else {
            menu.clear();
            settings = null;
        }
        return false;
    }

    private UiLifecycleHelper uiHelper;
    private Session.StatusCallback callback =
            new Session.StatusCallback() {
                @Override
                public void call(Session session,
                                 SessionState state, Exception exception) {
                    onSessionStateChange(session, state, exception);
                }
            };

    private void showFragment(int fragmentIndex, boolean addToBackStack) {
        FragmentManager fm = getSupportFragmentManager();
        FragmentTransaction transaction = fm.beginTransaction();
        for (int i = 0; i < fragments.length; i++) {
            if (i == fragmentIndex) {
                transaction.show(fragments[i]);
            } else {
                transaction.hide(fragments[i]);
            }
        }
        if (addToBackStack) {
            transaction.addToBackStack(null);
        }
        transaction.commit();
    }
}

package com.just.simply.myapplication；
导入android.content.Intent；
导入android.os.Bundle；
导入android.support.v4.app.Fragment；
导入android.support.v4.app.FragmentActivity；
导入android.support.v4.app.FragmentManager；
导入android.support.v4.app.FragmentTransaction；
导入android.view.Menu；
导入android.view.MenuItem；
导入com.facebook.Session；
导入com.facebook.SessionState；
导入com.facebook.ui生命周期帮助；
公共类MyActivity扩展了FragmentActivity{
私有静态最终int SPLASH=0；
私有静态最终整数选择=1；
专用静态最终整数设置=2；
私有静态最终整数片段计数=设置+1；
私有片段[]片段=新片段[Fragment_COUNT]；
私有布尔值isResumed=false；
私有菜单项设置；
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
uiHelper=新UiLifecycleHelper（此为回调）；
uiHelper.onCreate（savedInstanceState）；
setContentView（R.layout.activity_my）；
FragmentManager fm=getSupportFragmentManager（）；
片段[SPLASH]=fm.findFragmentById（R.id.splashFragment）；
片段[SELECTION]=fm.findFragmentById（R.id.selectionFragment）；
片段[SETTINGS]=fm.findFragmentById（R.id.userSettingsFragment）；
FragmentTransaction=fm.beginTransaction（）；
for（int i=0；i