RecyclerView没有显示

Question

I have some text views and a button to be displayed on top of a RecyclerView. I seem to be doing everything right, but somehow nothing is being displayed. I also checked thru logs and the RecyclerView should have data!

This is not the very first time to display RecyclerViews. However, this is the first time I am displaying a RecyclerView with some elements on top of it.

1. activity_home.xml - this is the main home page

     <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/home_RL" android:layout_width="match_parent" android:layout_height="match_parent"> <LinearLayout android:id="@+id/top_LL" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentTop="true" android:orientation="horizontal"> <EditText android:id="@+id/first_name" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="4dp" android:layout_weight="2" android:hint="FirstName" /> <EditText android:id="@+id/last_name" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="4dp" android:layout_weight="2" android:hint="LastName" /> <ProgressBar android:id="@+id/progress_bar" android:layout_width="wrap_content" android:layout_height="wrap_content" android:visibility="gone" /> <Button android:id="@+id/submit" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="4dp" android:layout_weight="1" android:onClick="goButton" android:text="GO" /> <Button android:id="@+id/load" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="4dp" android:layout_marginEnd="4dp" android:layout_weight="1" android:onClick="loadButton" android:text="L" /> </LinearLayout> <android.support.v7.widget.RecyclerView android:id="@+id/nameList" android:layout_below="@+id/top_LL" android:layout_width="match_parent" android:layout_height="wrap_content"> </android.support.v7.widget.RecyclerView></RelativeLayout> 

2. name_list_item.xml

    <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal"> <TextView android:id="@+id/list_first_name" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" tools:text="first name"/> <TextView android:id="@+id/list_last_name" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_weight="1" tools:text="second name"/> </LinearLayout> <View android:layout_width="match_parent" android:layout_height="1dp" android:background="@android:color/darker_gray" /> 

3. Name Adapter

   public class NameAdapter extends RecyclerView.Adapter {

     private List<Name> mNameList; private Context mContext; public NameAdapter(Context context) { mContext = context; } @Override public NameViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) { LayoutInflater inflater = LayoutInflater.from(viewGroup.getContext()); View view = inflater.inflate(R.layout.name_list_item, viewGroup, false); return new NameViewHolder(view); } @Override public void onBindViewHolder(final NameViewHolder nameViewHolder, int position) { String firstName = mNameList.get(position).getFirst(); String lastName = mNameList.get(position).getLast(); nameViewHolder.mListItemFirstName.setText(firstName); nameViewHolder.mListItemLastName.setText(lastName); } @Override public int getItemCount() { if (mNameList == null) { return 0; } return mNameList.size(); } class NameViewHolder extends RecyclerView.ViewHolder { TextView mListItemFirstName; TextView mListItemLastName; private NameViewHolder(View itemView) { super(itemView); mListItemFirstName = itemView.findViewById(R.id.list_first_name); mListItemLastName = itemView.findViewById(R.id.list_last_name); } } public void swapNameList(List<Name> nameList) { if (nameList != null) { nameList.clear(); } mNameList = nameList; this.notifyDataSetChanged(); } 

   }

UPDATE: ISSUE RESOLVED new code should be:

public void swapNameList(List<Name> nameList) {
                if (mNameList != null) {
                    mNameList.clear();
                }
                mNameList = nameList;
                this.notifyDataSetChanged();
            }    

Answer 1

The problem is here

   if (nameList != null) {
        nameList.clear();
    }

you are clearing the list you pass as parameter. This

public void swapNameList(List<Name> nameList) {
    mNameList = nameList;
    this.notifyDataSetChanged();
}

should fix it. (You don't need to clear anything since you are overriding the list every time you call swapNameList )

Answer 2

Solution: The problem here is you are carrying the list forward and clearing it off before assigning to the adapter, hence:

Instead of:

nameList.clear();

Write:

mNameList.clear();

That's all.