android 组件RecyclerView的使用指教?

想在首页使用RecyclerView来显示数据,因为使用了fragment所以我想在返回首页这一部分是填充数据,但是一直报错,这个控件不是太熟悉可以看看代码哪里有问题


MainActivaty

package com.example.fiz.myapplication;

import android.graphics.Color;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.RecyclerView.ViewHolder;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;

import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import java.util.ArrayList;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.LinearLayout;
import android.support.v7.widget.Toolbar;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private ViewPager mPager;
    private ArrayList<Fragment> fragmentsList;
    private LinearLayout ll_top;

    //首页组件定义
    private RecyclerView mRecyclerView;
    private List<String> mDatas;
    private HomeAdapter mAdapter;


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

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        toolbar.setTitle("demo");
        toolbar.setSubtitle("1234");
        toolbar.setLogo(R.drawable.ic_launcher);
        setSupportActionBar(toolbar);
        initView();


    }

    private void initView() {
        ll_top = (LinearLayout) findViewById(R.id.ll_top);
        mPager = (ViewPager) findViewById(R.id.vPager);
        fragmentsList = new ArrayList<Fragment>();
        //首页个recelerView添加数据

//        initData();
//        mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
//        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
//        mRecyclerView.setAdapter(mAdapter = new HomeAdapter());


        //

        Fragment activityfragment = TestFragment.newInstance("界面一");
        Fragment groupFragment = TestFragment.newInstance("界面2");
        Fragment friendsFragment = TestFragment.newInstance("界面3");
        Fragment chatFragment = TestFragment.newInstance("界面4");

        Fragment about = About.about("1234");
        Fragment homepage = HomePage.homePage("首页");


        fragmentsList.add(homepage);/**首页**/
        fragmentsList.add(groupFragment);
        fragmentsList.add(friendsFragment);
        fragmentsList.add(chatFragment);

        mPager.setAdapter(new MyFragmentPagerAdapter(
                getSupportFragmentManager(), fragmentsList));
        mPager.setCurrentItem(0);

        BottomTabBar navigationBar = new BottomTabBar(this);
        ll_top.setBackgroundColor(Color.parseColor("#F8F8FF"));
        navigationBar.attachToParent(ll_top, new String[]{"首页", "消息", "发现",
                "我"}, mPager);
    }

    protected void initData() {
        mDatas = new ArrayList<String>();
        for (int i = 'A'; i < 'z'; i++) {
            mDatas.add("this is a demo---" + (char) i);
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public class MyFragmentPagerAdapter extends FragmentPagerAdapter {

        private ArrayList<Fragment> fragmentsList;

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

        public MyFragmentPagerAdapter(FragmentManager fm,
                                      ArrayList<Fragment> fragments) {
            super(fm);
            this.fragmentsList = fragments;
        }

        @Override
        public int getCount() {
            return fragmentsList.size();
        }

        @Override

        public Fragment getItem(int arg0) {


            return fragmentsList.get(arg0);
        }

        @Override
        public int getItemPosition(Object object) {
            return super.getItemPosition(object);
        }

    }

    class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder>
    {

        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
        {
            MyViewHolder holder = new MyViewHolder(LayoutInflater.from(
                    MainActivity.this).inflate(R.layout.item_home, parent,
                    false));
            return holder;
        }

        @Override
        public void onBindViewHolder(MyViewHolder holder, int position)
        {
            holder.tv.setText(mDatas.get(position));
        }

        @Override
        public int getItemCount()
        {
            return mDatas.size();
        }

        class MyViewHolder extends ViewHolder
        {

            TextView tv;

            public MyViewHolder(View view)
            {
                super(view);
                tv = (TextView) view.findViewById(R.id.id_num);
            }
        }
    }
}

布局文件

home_page

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/my_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scrollbars="vertical"/>
</RelativeLayout>

item_home

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:background="#44ff0000"
    android:layout_height="wrap_content" >

    <TextView
        android:id="@+id/id_num"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:gravity="center"
        android:text="1" />
</FrameLayout>

HomePage

@SuppressLint("ValidFragment")
public class HomePage extends Fragment {
    private String textString;
//首页组件


    public HomePage(String textString) {
        this.textString = textString;
    }

    public static HomePage homePage(String textString) {
        HomePage myabout = new HomePage(textString);
        return myabout;
    }

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

        return view;
    }

}

异常报错信息

03-19 23:41:20.809 3818-3818/? E/AndroidRuntime: FATAL EXCEPTION: main
 Process: com.example.fiz.myapplication, PID: 3818
 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.fiz.myapplication/com.example.fiz.myapplication.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416)
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476)
     at android.app.ActivityThread.-wrap11(ActivityThread.java)
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344)
     at android.os.Handler.dispatchMessage(Handler.java:102)
     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$MethodAndArgsCaller.run(ZygoteInit.java:726)
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
  Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
     at com.example.fiz.myapplication.MainActivity.initView(MainActivity.java:77)
     at com.example.fiz.myapplication.MainActivity.onCreate(MainActivity.java:64)
     at android.app.Activity.performCreate(Activity.java:6237)
     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107)
     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369)
     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) 
     at android.app.ActivityThread.-wrap11(ActivityThread.java) 
     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) 
     at android.os.Handler.dispatchMessage(Handler.java:102) 
     at android.os.Looper.loop(Looper.java:148) 
     at android.app.ActivityThread.main(ActivityThread.java:5417) 
     at java.lang.reflect.Method.invoke(Native Method) 
     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
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