のLayoutManager - nullポインタ例外私はrecyclerviewとcardviewで、Androidアプリに取り組んでいます画面

Question

を回転させたとき、すべてが素晴らしい作品が、私は、画面を回転させたときに、アプリケーションが停止し、私は

recyclerView.setLayoutManager(mLayoutManager); 

でNullPointerExceptionが取得

これは完全な例外です：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.news.press/com.news.press.activities.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:3150) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3260) 
        at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:5200) 
        at android.app.ActivityThread.access$1100(ActivityThread.java:218) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1740) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        at android.os.Looper.loop(Looper.java:145) 
        at android.app.ActivityThread.main(ActivityThread.java:6934) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at java.lang.reflect.Method.invoke(Method.java:372) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199) 
       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference 
        at com.news.press.activities.MainActivity.onCreate(MainActivity.java:88) 
        at android.app.Activity.performCreate(Activity.java:6609) 
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134) 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3103) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3260)  
        at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:5200)  
        at android.app.ActivityThread.access$1100(ActivityThread.java:218)  
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1740)  
        at android.os.Handler.dispatchMessage(Handler.java:102)  
        at android.os.Looper.loop(Looper.java:145)  
        at android.app.ActivityThread.main(ActivityThread.java:6934)  
        at java.lang.reflect.Method.invoke(Native Method)  
        at java.lang.reflect.Method.invoke(Method.java:372)  
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)  
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199) 

、これが私のxmlレイアウトである

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    xmlns:app="http://schemas.android.com/apk/res-auto" 
    android:id="@+id/content_main" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" 
    app:layout_behavior="@string/appbar_scrolling_view_behavior" 
    tools:context="com.news.press.activities.MainActivity" 
    android:layoutDirection="rtl" 
    android:textDirection="rtl"> 

    <android.support.v7.widget.RecyclerView 
     android:id="@+id/recycler_view" 
     android:layout_width="match_parent" 
     android:layout_height="wrap_content" 
     android:clipToPadding="false" 
     android:scrollbars="none" 
     /> 
</RelativeLayout> 

UPDATE：

私のJavaコード

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

     Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
     setSupportActionBar(toolbar); 

     DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
     ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
      this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
     drawer.setDrawerListener(toggle); 
     toggle.syncState(); 

     NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
     navigationView.setNavigationItemSelectedListener(this); 

     /** 
     * setting homepage Content 
     */ 

     recyclerView = (RecyclerView) findViewById(R.id.recycler_view); 
     articlesList = new ArrayList<>(); 
     adapter = new ArticleAdapter(this, articlesList); 

     RecyclerView.LayoutManager mLayoutManager = new GridLayoutManager(this,1); 
     recyclerView.setLayoutManager(mLayoutManager); 
     recyclerView.addItemDecoration(new GridSpacingItemDecoration(1, dpToPx(1), true)); 
     recyclerView.setItemAnimator(new DefaultItemAnimator()); 
     recyclerView.setAdapter(adapter); 

     prepareArticles(); 
    } 

Answer 1

すべては私のためにかなり明確ようです。

土地の向きに別のレイアウトがないことを確認できますか？ この他のレイアウトにはrecyclerviewはありませんか？