在Fragment中将setAdapter用于RecyclerView时出错

Question

我想在JSON中使用Fragment中的recyclerView解析一切正常，但是当我尝试设置recyclerView适配器时，它给出了错误

这是MainActivity的代码

 protected void onPostExecute(Integer result) {
        // Download complete. Let us update UI
      //  homeFragment.mProgressBar.setVisibility(View.GONE);

        if (result == 1) {
            new Thread(new Runnable() {
                @Override
                public void run() {
                    homeFragment.mAdapter = new MembersAdapter(homeFragment.membersList);
                    MainActivity.this.runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            homeFragment.mRecyclerView.setAdapter(homeFragment.mAdapter);
                        }
                    });
                }
            }).start();

这是片段HomeFragment

 @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {

    View home_view = inflater.inflate(R.layout.list_view, container, false);

    mRecyclerView = (RecyclerView) home_view.findViewById(R.id.recycler_view);
    mRecyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
    mRecyclerView.setItemAnimator(new DefaultItemAnimator());

    mProgressBar = (ProgressBar) home_view.findViewById(R.id.progress_bar);
    mProgressBar.setVisibility(View.VISIBLE);
    mProgressBar.setVisibility(View.GONE);


    MainActivity activity = (MainActivity) getActivity();

    activity.Senturl = "http://javatechig.com/?json=get_recent_posts&count=45";

    activity.download.execute(activity.Senturl);

    return home_view;

这是适配器和视图架

public class MembersAdapter extends RecyclerView.Adapter<MembersAdapter.MemberViewHolder>
{
    private List<Members> membersList;
    private Context mContext;
    public MembersAdapter( List <Members> membersList)
        {
            this.membersList=membersList;
            //this.mContext=context;
        }
    @Override
    public MemberViewHolder onCreateViewHolder (ViewGroup parent,int viewType)
        {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.card_view, null);
            MemberViewHolder memberHolder =new MemberViewHolder(view);
            return memberHolder;
        }
    @Override
    public void onBindViewHolder (MemberViewHolder holder,int position)
        {
        Members member = membersList.get(position);

        Picasso.with(mContext).load(member.getThumbnail()).error(R.drawable.games).placeholder(R.drawable.about).into(holder.imageView);
        holder.textView.setText(Html.fromHtml(member.getTitle()));
        //holder.tvShort_Description.setText(member.getShort_description());
        //holder.tvDate.setText(member.getDate());

        }
    @Override
    public int  getItemCount()
            {
                return (null != membersList ? membersList.size() : 0);
            }

    public class MemberViewHolder extends RecyclerView.ViewHolder
    {
        protected TextView textView;//,tvShort_Description,tvDate;
        public ImageView imageView;

        public MemberViewHolder(View view)
        {
            super (view);
            this.imageView=(ImageView)view.findViewById(R.id.thumbnail);
            this.textView=(TextView)view.findViewById(R.id.title);
        }

    }

}

最后是错误开始的logcat

09-18 10:27:26.769    2161-2161/com.dushyant30suthar.gitsevent W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xa62f2288)
09-18 10:27:26.769    2161-2161/com.dushyant30suthar.gitsevent E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.NullPointerException
at com.dushyant30suthar.gitsevent.MainActivity$MainActivityData$1$1.run(MainActivity.java:201) at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137
at android.app.ActivityThread.main(ActivityThread.java:4745)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
        at dalvik.system.NativeStart.main(Native Method)

Answer 1

只需在直接的postExceute方法中设置适配器

protected void onPostExecute(Integer result) {

        if (result == 1) {

                    homeFragment.mAdapter = new MembersAdapter(homeFragment.membersList);

                    homeFragment.mRecyclerView.setAdapter(homeFragment.mAdapter);

                }
            }).start();

Answer 2

在调用setAdapter之前检查homeFragment.mAdapter是否不为null