在android studio中升级repo v9后，片段必须是公共静态类崩溃错误

我是一个非常熟悉Android的新手。我想创建一个有3个水平页面的活动。每个页面都有一个网格视图。我使用ViewPager创建页面，并对每个页面使用GridView。下面是代码

public class CategoryActivity extends ActionBarActivity {

    static final int NUM_ITEMS = 3;

    MyAdapter mAdapter;

    ViewPager mPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_pager);

        getSupportActionBar().hide();

        mAdapter = new MyAdapter(this.getSupportFragmentManager());

        mPager = (ViewPager)findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);

    }

    //MyAdapter is adapter for Pager
    public class MyAdapter extends FragmentPagerAdapter {

        ArrayList<ArrayListFragment> fragments;
        public MyAdapter(FragmentManager fm) {
            super(fm);

            fragments = new ArrayList<>();

            for (int i = 0; i < NUM_ITEMS; i++) {
                ArrayListFragment f = new ArrayListFragment();

                fragments.add(f);
            }
       }

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

        @Override
        public Fragment getItem(int position) {

            //For each page -> get fragment for that page
            ArrayListFragment f = fragments.get(position);

            return f;
        }
    }

    //Adapter for each grid view in each Page
    public class ImageAdapter extends BaseAdapter {
        private Context mContext;
        private View parentView;

        public ImageAdapter(Context c) {
            mContext = c;
        }

        public ImageAdapter(Context c, View aParentView) {
            mContext = c;
            parentView = aParentView;
        }

        public int getCount() {
            return mThumbIds.length;
        }

        public Object getItem(int position) {
            return null;
        }

        public long getItemId(int position) {
            return 0;
        }

        // create a new ImageView for each item referenced by the Adapter
        public View getView(int position, View convertView, ViewGroup parent)        {
            View itemView;
            if (convertView == null) {

                //I really config view for each item in grid view....
                //The problem is not here
                //..........
            }
            return itemView;
        }

        // references to our images
        private Integer[] mThumbIds = {
                R.drawable.images, R.drawable.images,
                R.drawable.images, R.drawable.images,
                R.drawable.images, R.drawable.images,
                R.drawable.images, R.drawable.images,
                R.drawable.images, R.drawable.images,
                R.drawable.images, R.drawable.images
        };
    }

    public class ArrayListFragment extends Fragment {

        /**
         * When creating, retrieve this instance's number from its arguments.
         */
        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
        }

        /**
         * The Fragment's UI is just a simple text view showing its
         * instance number.
         */
        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            final View v = inflater.inflate(R.layout.fragment_pager_list, container, false);

            GridView gridview = (GridView) v.findViewById(R.id.categridview);

            ImageAdapter ia = new ImageAdapter(CategoryActivity.this, gridview);
            gridview.setAdapter(ia);

            return v;
        }


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

        }

    }
}

公共类CategoryActivity扩展了ActionBarActivity{
静态最终整数项目=3；
MyAdapter mAdapter；
可视寻呼机；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.fragment_pager）；
getSupportActionBar（）.hide（）；
mAdapter=newMyAdapter（this.getSupportFragmentManager（））；
mPager=（ViewPager）findViewById（R.id.pager）；
mPager.setAdapter（mAdapter）；
}
//MyAdapter是寻呼机的适配器
公共类MyAdapter扩展了FragmentPagerAdapter{
ArrayList

及


为什么ArrayListFragment必须是一个公共静态类，我想每个类都必须有一个单独的片段

这里的问题是什么，有人能帮我弄清楚ArrayListFragment和CategoryActivity在同一个java文件中吗？如果是真的，静态类意味着可以创建ArrayListFragment的实例而不创建CategoryActivity的实例。因此每个类都可以有自己的ArrayListFragment实例。
是的，所有都在一个类中java文件。但我不太明白，你能解释得更清楚些吗。我应该怎么做？顺便说一下，我从另一个活动创建了CategoryActivity的实例，只是创建了CategoryActivity的意图并启动它，没有什么特别的。CategoryActivity类中的所有代码都显示在上面，当然没有更多。阅读嵌套类关于java及其实例化规则。您应该为ArrayListFragment（和其他片段）创建单独的java文件，或者将嵌套的片段类声明为静态。下面是一些有用的链接：感谢Viktor Dolgalyov，我将ArrayListFragment移动到另一个java文件，它可以工作。我应该阅读更多有关它的信息
E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: <my project process>, PID: 1901
                  java.lang.IllegalStateException: Fragment <my project package>.CategoryActivity.ArrayListFragment must be a public static class to be  properly recreated from instance state.
                      at android.support.v4.app.BackStackRecord.doAddOp(BackStackRecord.java:435)
                      at android.support.v4.app.BackStackRecord.add(BackStackRecord.java:426)
                      at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:103)
                      at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:1006)
                      at android.support.v4.view.ViewPager.populate(ViewPager.java:1154)
                      at android.support.v4.view.ViewPager.populate(ViewPager.java:1088)
                      at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1614)
                      at android.view.View.measure(View.java:18788)
                      at android.widget.LinearLayout.measureVertical(LinearLayout.java:901)
                      at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
                      at android.view.View.measure(View.java:18788)
                      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                      at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
                      at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)
                      at android.view.View.measure(View.java:18788)
                      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                      at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:389)
                      at android.view.View.measure(View.java:18788)
                      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                      at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
                      at android.view.View.measure(View.java:18788)
                      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
                      at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
                      at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
                      at android.view.View.measure(View.java:18788)
                      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
                      at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
                      at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)
                      at android.view.View.measure(View.java:18788)
                      at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2100)
                      at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1216)
                      at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1452)
                      at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1107)
                      at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6013)
                      at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
                      at android.view.Choreographer.doCallbacks(Choreographer.java:670)
                      at android.view.Choreographer.doFrame(Choreographer.java:606)
                      at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
                      at android.os.Handler.handleCallback(Handler.java:739)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:148)
                      at android.app.ActivityThread.main(ActivityThread.java:5417)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
I/Process: Sending signal. PID: 1901 SIG: 9
Application terminated.