Question

我是Android的初学者。我试图在片段中使用Recycler View作为导航抽屉的一部分。以下是片段代码：

RecyclerFragment.java

public View onCreateView(LayoutInflater inflater, ViewGroup container,  Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.recyclerfragment,container,false);


    navTitles = getResources().getStringArray(R.array.navDrawerItems);
    navIcons = getResources().obtainTypedArray(R.array.navDrawerIcons);
    recyclerViewAdapter = new Adapter(navTitles,navIcons,this.activity);
   recyclerView = (RecyclerView) v.findViewById(R.id.recyclerView);
    recyclerView.setAdapter(recyclerViewAdapter);
    recyclerView.setLayoutManager(new LinearLayoutManager(this.activity));
    return v;
}

@Override
public void onAttach(Context context) {
    super.onAttach(context);
    this.activity=(MainActivity)context;
}
 @Override
    public void onAttach(Activity activity){
     super.onAttach(activity);
    this.activity=activity;


}

适配器代码：

Adapter(String[] titles , TypedArray icons , Context context){

    this.titles = titles;
    this.icons = icons;
    this.context = context;
   //inflator=LayoutInflater.from(context);
}

public class ViewHolder extends RecyclerView.ViewHolder  {

    TextView  navTitle;
    ImageView navIcon;
    Context context;

    public ViewHolder(View drawerItem , int itemType , Context context){

        super(drawerItem);
        this.context = context;
      //  drawerItem.setOnClickListener(this);
        if(itemType==1){
            navTitle = (TextView) itemView.findViewById(R.id.tv_NavTitle);
            navIcon = (ImageView) itemView.findViewById(R.id.iv_NavIcon);
        }
    }
}

 @Override
 public Adapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

    LayoutInflater layoutInflater = (LayoutInflater) parent.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

    if(viewType==1){
        View itemLayout =   layoutInflater.inflate(R.layout.drawer_item_layout,null);
        return new ViewHolder(itemLayout,viewType,context);
    }
    else if (viewType==0) {
        View itemHeader = layoutInflater.inflate(R.layout.header_layout,null);
        return new ViewHolder(itemHeader,viewType,context);
    }
    return null;
}
@Override
public void onBindViewHolder(Adapter.ViewHolder holder, int position) {

    if(position!=0){
        holder.navTitle.setText(titles[position - 1]);
        holder.navIcon.setImageResource(icons.getResourceId(position-1,-1));
    }
}
@Override
public int getItemCount() {
    return titles.length+1;
}
@Override
public int getItemViewType(int position) {
    if(position==0)return 0;
    else return 1;
}

但是当我运行应用程序时，我得到了Log Cat：

02-27 20:38:41.848 25007-25007/com.example.hp.recyclernavigation E/RecyclerView: No adapter attached; skipping layout
02-27 20:38:47.693 25007-25007/com.example.hp.recyclernavigation E/RecyclerView: No adapter attached; skipping layout
02-27 20:39:13.730 25007-25007/com.example.hp.recyclernavigation E/RecyclerView: No adapter attached; skipping layout
02-27 20:39:13.816 25007-25007/com.example.hp.recyclernavigation E/RecyclerView: No adapter attached; skipping layout
02-27 20:39:14.271 25007-25007/com.example.hp.recyclernavigation E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                 Process: com.example.hp.recyclernavigation, PID: 25007
                                                                                 java.lang.NullPointerException: Attempt to invoke virtual method 'boolean   android.support.v7.widget.RecyclerView$LayoutManager.canScrollVertically()' on a   null object reference
                                                                                  at  android.support.v7.widget.RecyclerView.computeVerticalScrollRange(RecyclerView.j    ava:1581)
                                                                                     at android.view.View.onDrawScrollBars(View.java:12837)
                                                                                   at android.view.View.draw(View.java:15138)
                                                                                    at android.support.v7.widget.RecyclerView.draw(RecyclerView.java:3171)
                                                                                     at android.view.View

有人可以帮我解决这个问题。

编辑：

这是activity_main.xml：

<android.support.v4.widget.DrawerLayout   xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:local="http://schemas.android.com/apk/res-auto"
android:id="@+id/drawerMainActivity"
android:layout_width="match_parent"
android:layout_height="match_parent">

  <LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <include android:id="@+id/toolBar"
        layout="@layout/app_bar"/>
  </LinearLayout>
  <FrameLayout
    android:orientation="vertical"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:id="@+id/containerView">


  </FrameLayout>
  <fragment
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:name="com.example.hp.recyclernavigation.RecyclerFragment"
    android:id="@+id/fragment"
    >

    <android.support.v7.widget.RecyclerView
        android:layout_width="240dp"
        android:layout_height="match_parent"
        android:id="@+id/recyclerView"
        android:scrollbars="vertical"
        android:background="#FFFFFF"
        android:layout_gravity="left"
        />
</fragment>
</android.support.v4.widget.DrawerLayout>

Answer 1

像这样修改你的代码：

recyclerViewAdapter = new Adapter(navTitles,navIcons,getActivity().getApplicationContext());
recyclerView = (RecyclerView) v.findViewById(R.id.recyclerView);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity().getApplicationContext()));
recyclerView.setAdapter(recyclerViewAdapter);

首先，你必须设置布局管理器，然后设置适配器!!!

没有连接适配器;跳过布局错误

1 个答案: