RecyclerView - 交互のレイアウト

Question

私はこれでとても新しいです。ここでは簡単なRecyclerViewのコードを示します。 LayoutManagerのStaggeredGridLayoutとLinearLayoutを交互に使用したいと思います。

どのように両方のレイアウトを開始しましたか？

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

    RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view); 
    recyclerView.setHasFixedSize(true); 

    staggeredGrid = new StaggeredGridLayoutManager(2, 1); 
    cardView = new LinearLayoutManager(this); 
    recyclerView.setLayoutManager(staggeredGrid); 

    List<ItemObjects> staggeredList = getListItemData(); 

    RecyclerViewAdapter adapter = new RecyclerViewAdapter(MainActivity.this, staggeredList); 
    recyclerView.setAdapter(adapter); 
} 

どのように単純なボタンでそれらの間を交互にしようとしましたか。すべてのコードが必要かどうかはわかりませんが、ビューを切り替えて再構築するたびにアダプターを無効にしておく方が良いという情報がありました。

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    int id = item.getItemId(); 

    if (id == R.id.view_settings) { 
     if (recyclerView.getLayoutManager() == staggeredGrid) { 
      recyclerView.setAdapter(null); 
      recyclerView.setLayoutManager(cardView); 
      recyclerView.setAdapter(adapter); 
      return true; 
     } 

     if (recyclerView.getLayoutManager() == cardView) { 
      recyclerView.setAdapter(null); 
      recyclerView.setLayoutManager(staggeredGrid); 
      recyclerView.setAdapter(adapter); 
      return true; 
     } 

    } 

    return super.onOptionsItemSelected(item); 
} 

エラーが発生しました。

09-06 22:17:37.769 11853-11853/com.example.wsdw E/AndroidRuntime: FATAL EXCEPTION: main 
                   Process: com.example.wsdw, PID: 11853 
                   java.lang.NullPointerException: Attempt to invoke virtual method 'android.support.v7.widget.RecyclerView$LayoutManager android.support.v7.widget.RecyclerView.getLayoutManager()' on a null object reference 
                    at com.example.wsdw.MainActivity.onOptionsItemSelected(MainActivity.java:50) 
                    at android.app.Activity.onMenuItemSelected(Activity.java:2908) 
                    at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:406) 
                    at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:195) 
                    at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:103) 
                    at android.support.v7.app.AppCompatDelegateImplV9.onMenuItemSelected(AppCompatDelegateImplV9.java:667) 
                    at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:810) 
                    at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152) 
                    at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:957) 
                    at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:947) 
                    at android.support.v7.widget.ActionMenuView.invokeItem(ActionMenuView.java:616) 
                    at android.support.v7.view.menu.ActionMenuItemView.onClick(ActionMenuItemView.java:153) 
                    at android.view.View.performClick(View.java:5198) 
                    at android.view.View$PerformClick.run(View.java:21147) 
                    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) 

私が知っているすべてのために、これは完全に間違って行っている可能性が、誰が助けることができる場合、私は出発点を探しています。どうかありがとうございます。

Answer 1

RecyclerView recyclerView; 
//Your Activity Name 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 

    recyclerView = (RecyclerView) findViewById(R.id.recycler_view); 
    recyclerView.setHasFixedSize(true); 

    staggeredGrid = new StaggeredGridLayoutManager(2, 1); 
    cardView = new LinearLayoutManager(this); 
    recyclerView.setLayoutManager(staggeredGrid); 

    List<ItemObjects> staggeredList = getListItemData(); 

    RecyclerViewAdapter adapter = new RecyclerViewAdapter(MainActivity.this, staggeredList); 
    recyclerView.setAdapter(adapter); 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    int id = item.getItemId(); 

    if (id == R.id.view_settings) { 
     if (recyclerView.getLayoutManager() == staggeredGrid) { 
      recyclerView.setAdapter(null); 
      recyclerView.setLayoutManager(cardView); 
      recyclerView.setAdapter(adapter); 
      adapter. notifyDataSetChanged(); 
      return true; 
     } 

     if (recyclerView.getLayoutManager() == cardView) { 
      recyclerView.setAdapter(null); 
      recyclerView.setLayoutManager(staggeredGrid); 
      recyclerView.setAdapter(adapter); 
      adapter. notifyDataSetChanged(); 
      return true; 
     } 

    } 

    return super.onOptionsItemSelected(item); 
}