选项卡式android应用程序在转到另一个选项卡（android->；java->；android studio）时崩溃

我用android开发的预览应用程序声明，当转到另一个选项卡时，该应用程序在模拟器中崩溃。 以下是日志输出：

01-04 11:02:19.103    2495-2495/com.example.android.effectivenavigation          D/AndroidRuntime﹕ Shutting down VM
01-04 11:02:19.103    2495-2495/com.example.android.effectivenavigation W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb0ccfb20)
01-04 11:02:19.103    2495-2495/com.example.android.effectivenavigation E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.android.effectivenavigation, PID: 2495
java.lang.NullPointerException
        at com.example.android.effectivenavigation.MainActivity$AppSectionsPagerAdapter$DummySectionFragment.onCreateView(MainActivity.java:194)
        at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
        at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
        at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:486)
        at android.support.v4.app.FragmentPagerAdapter.finishUpdate(FragmentPagerAdapter.java:141)
        at android.support.v4.view.ViewPager.populate(ViewPager.java:1073)
        at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:555)
        at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:514)
        at android.support.v4.view.ViewPager.setCurrentItem(ViewPager.java:495)
        at com.example.android.effectivenavigation.MainActivity.onTabSelected(MainActivity.java:100)
        at com.android.internal.app.ActionBarImpl.selectTab(ActionBarImpl.java:577)
        at com.android.internal.app.ActionBarImpl$TabImpl.select(ActionBarImpl.java:1105)
        at com.android.internal.widget.ScrollingTabContainerView$TabClickListener.onClick(ScrollingTabContainerView.java:547)
        at android.view.View.performClick(View.java:4438)
        at android.view.View$PerformClick.run(View.java:18422)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)

下面是该应用程序的主要活动

/*
 * Copyright 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.effectivenavigation;

import android.app.ActionBar;
import android.app.FragmentTransaction;
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.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MainActivity extends FragmentActivity implements ActionBar.TabListener {

/**
 * The {@link android.support.v4.view.PagerAdapter} that will provide fragments for each of the
 * three primary sections of the app. We use a {@link android.support.v4.app.FragmentPagerAdapter}
 * derivative, which will keep every loaded fragment in memory. If this becomes too memory
 * intensive, it may be best to switch to a {@link android.support.v4.app.FragmentStatePagerAdapter}.
 */
AppSectionsPagerAdapter mAppSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will display the three primary sections of the app, one at a
 * time.
 */
ViewPager mViewPager;

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    // Create the adapter that will return a fragment for each of the three primary sections
    // of the app.
    mAppSectionsPagerAdapter = new AppSectionsPagerAdapter(getSupportFragmentManager());

    // Set up the action bar.
    final ActionBar actionBar = getActionBar();

    // Specify that the Home/Up button should not be enabled, since there is no hierarchical
    // parent.
    actionBar.setHomeButtonEnabled(false);

    // Specify that we will be displaying tabs in the action bar.
    actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

    // Set up the ViewPager, attaching the adapter and setting up a listener for when the
    // user swipes between sections.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setAdapter(mAppSectionsPagerAdapter);
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(int position) {
            // When swiping between different app sections, select the corresponding tab.
            // We can also use ActionBar.Tab#select() to do this if we have a reference to the
            // Tab.
            actionBar.setSelectedNavigationItem(position);
        }
    });

    // For each of the sections in the app, add a tab to the action bar.
    for (int i = 0; i < mAppSectionsPagerAdapter.getCount(); i++) {
        // Create a tab with text corresponding to the page title defined by the adapter.
        // Also specify this Activity object, which implements the TabListener interface, as the
        // listener for when this tab is selected.
        actionBar.addTab(
                actionBar.newTab()
                        .setText(mAppSectionsPagerAdapter.getPageTitle(i))
                        .setTabListener(this));
    }
}

@Override
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}

@Override
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
    // When the given tab is selected, switch to the corresponding page in the ViewPager.
    mViewPager.setCurrentItem(tab.getPosition());
}

@Override
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction fragmentTransaction) {
}

/**
 * A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
 * sections of the app.
 */
public static class AppSectionsPagerAdapter extends FragmentPagerAdapter {

    public AppSectionsPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public Fragment getItem(int i) {
        switch (i) {
            case 0:
                // The first section of the app is the most interesting -- it offers
                // a launchpad into the other demonstrations in this example application.
                return new slaapkamer();
            case 1:
                return new woonkamer();
            default:
                // The other sections of the app are dummy placeholders.
                Fragment fragment = new DummySectionFragment();
                Bundle args = new Bundle();
                args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
                fragment.setArguments(args);
                return fragment;
        }
    }

    @Override
    public int getCount() {
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        if (position == 0) {
            return "slaapkamer";
        } else if (position == 1) {
            return "woonkamer";
        } else {
            return "geavanceerd";
        }
    }

    /**
     * A fragment that launches other parts of the demo application.
     */
    public static class slaapkamer extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);
            //place the shit that should happen


            return rootView;
        }
    }

    public static class woonkamer extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_launchpad2, container, false);

            //place the shit that should happen

            return rootView;
        }
    }


    /**
     * A dummy fragment representing a section of the app, but that simply displays dummy text.
     */
    public static class DummySectionFragment extends Fragment {

        public static final String ARG_SECTION_NUMBER = "section_number";

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
            Bundle args = getArguments();
            ((TextView) rootView.findViewById(android.R.id.text1)).setText(
                    getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }
    }
}
}

/*
*版权所有2012安卓开源项目
*
*根据Apache许可证2.0版（以下简称“许可证”）获得许可；
*除非遵守许可证，否则不得使用此文件。
*您可以通过以下方式获得许可证副本：
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
*除非适用法律要求或书面同意，软件
*根据许可证进行的分发是按“原样”进行分发的，
*无任何明示或暗示的保证或条件。
*请参阅许可证以了解管理权限和权限的特定语言
*许可证下的限制。
*/
包com.example.android.effectivenavigation；
导入android.app.ActionBar；
导入android.app.FragmentTransaction；
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.FragmentPagerAdapter；
导入android.support.v4.view.ViewPager；
导入android.view.LayoutInflater；
导入android.view.view；
导入android.view.ViewGroup；
导入android.widget.TextView；
公共类MainActivity扩展FragmentActivity实现ActionBar.TabListener{
/**
*{@link android.support.v4.view.PagerAdapter}，它将为每个
*应用程序的三个主要部分。我们使用{@linkandroid.support.v4.app.FragmentPagerAdapter}
*派生，它将把每个加载的片段都保存在内存中。如果这变得太内存化
*因此，最好切换到{@linkandroid.support.v4.app.FragmentStatePagerAdapter}。
*/
应用分区SPAGERAAdapter映射分区SPAGERAAdapter；
/**
*{@link ViewPager}将显示应用程序的三个主要部分，一次一个
*时间。
*/
ViewPager mViewPager；
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
//创建适配器，该适配器将为三个主要部分中的每个部分返回一个片段
//应用程序的名称。
mAppSectionsPagerAdapter=新的AppSectionsPagerAdapter（getSupportFragmentManager（））；
//设置操作栏。
最终ActionBar ActionBar=getActionBar（）；
//指定不应启用Home/Up按钮，因为没有层次结构
//家长。
actionBar.setHomeButtonEnabled（假）；
//指定我们将在操作栏中显示选项卡。
actionBar.setNavigationMode（actionBar.NAVIGATION\u MODE\u选项卡）；
//设置ViewPager，连接适配器并设置侦听器，以便
//用户在分区之间滑动。
mViewPager=（ViewPager）findViewById（R.id.pager）；
mViewPager.setAdapter（mAppSectionsPagerAdapter）；
mViewPager.setOnPageChangeListener（新的ViewPager.SimpleOnPageChangeListener（）{
@凌驾
已选择页面上的公共无效（内部位置）{
//在不同的应用程序分区之间滑动时，请选择相应的选项卡。
//如果有对
//标签。
actionBar.setSelectedNavigationItem（位置）；
}
});
//对于应用程序中的每个部分，在操作栏中添加一个选项卡。
对于（int i=0；i/**
 * A dummy fragment representing a section of the app, but that simply displays dummy text.
 */
public static class DummySectionFragment extends Fragment {

    public static final String ARG_SECTION_NUMBER = "section_number";

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
        Bundle args = getArguments();
        if (args != null) {
            ((TextView) rootView.findViewById(R.id.text1)).setText(
                    getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
        }
        return rootView;
    }
}