android - 从 IntentService 添加数据时，recyclerview 崩溃

Question

当我尝试从 intentservice 添加新数据到 recyclerview 时，当从 intentservice 的 addMsg 函数调用以下行时，我收到以下错误。我该如何解决它？

 new SimpleStringRecyclerViewAdapter(getBaseContext()).notifyDataSetChanged();

错误:

  java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources$Theme android.content.Context.getTheme()' on a null object reference
       at com.example.chat$SimpleStringRecyclerViewAdapter.<init>(chat.java:471)
       at com.example.chat$8.run(chat.java:639)

完整代码:

     public class CheeseListFragment extends Activity {


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


            setupRecyclerView(rv);

        }

        private void setupRecyclerView(RecyclerView recyclerView) {
            recyclerView.setLayoutManager(new LinearLayoutManager(recyclerView.getContext()));
            recyclerView.setAdapter(new SimpleStringRecyclerViewAdapter(getActivity(),
                    getRandomSublist(Cheeses.sCheeseStrings, 30)));
        }

        private List<String> getRandomSublist(String[] array, int amount) {
            ArrayList<String> list = new ArrayList<>(amount);
            Random random = new Random();
            while (list.size() < amount) {
                list.add(array[random.nextInt(array.length)]);
            }
            return list;
        }

        public static class SimpleStringRecyclerViewAdapter
                extends RecyclerView.Adapter<SimpleStringRecyclerViewAdapter.ViewHolder> {

            private final TypedValue mTypedValue = new TypedValue();
            private int mBackground;
            private List<String> mValues;

            public static class ViewHolder extends RecyclerView.ViewHolder {
                public String mBoundString;

                public final View mView;
                public final ImageView mImageView;
                public final TextView mTextView;

                public ViewHolder(View view) {
                    super(view);
                    mView = view;
                    mImageView = (ImageView) view.findViewById(R.id.avatar);
                    mTextView = (TextView) view.findViewById(android.R.id.text1);
                }

                @Override
                public String toString() {
                    return super.toString() + " '" + mTextView.getText();
                }
            }

            public String getValueAt(int position) {
                return mValues.get(position);
            }

            public SimpleStringRecyclerViewAdapter(Context context, List<String> items) {
                context.getTheme().resolveAttribute(R.attr.selectableItemBackground, mTypedValue, true);
                mBackground = mTypedValue.resourceId;
                mValues = items;
            }

            @Override
            public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.list_item, parent, false);
                view.setBackgroundResource(mBackground);
                return new ViewHolder(view);
            }

            @Override
            public void onBindViewHolder(final ViewHolder holder, int position) {
                holder.mBoundString = mValues.get(position);
                holder.mTextView.setText(mValues.get(position));

                holder.mView.setOnClickListener(new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Context context = v.getContext();
                        Intent intent = new Intent(context, CheeseDetailActivity.class);
                        intent.putExtra(CheeseDetailActivity.EXTRA_NAME, holder.mBoundString);

                        context.startActivity(intent);
                    }
                });

                Glide.with(holder.mImageView.getContext())
                        .load(Cheeses.getRandomCheeseDrawable())
                        .fitCenter()
                        .into(holder.mImageView);
            }

            @Override
            public int getItemCount() {
                return mValues.size();
            }
        }

 public void addMsg(String  msg_text){

        new Handler(Looper.getMainLooper()).post(new Runnable() {
            @Override
            public void run() {


                mValues.add(chatmodel);

                new SimpleStringRecyclerViewAdapter(getBaseContext()).notifyDataSetChanged();
                recyclerView.setLayoutManager(new LinearLayoutManager(chat.getContext()));
                recyclerView.setAdapter(new SimpleStringRecyclerViewAdapter(getBaseContext()));
                recyclerView.scrollToPosition(mValues.add.size() - 1);



            }
        });
    }

Answer 1

恕我直言，您遇到了上下文问题。

 new SimpleStringRecyclerViewAdapter(getBaseContext()).notifyDataSetChanged();

Adapter 使用 context 获取 LayoutInflater 和 inflate Views，所以你需要传递 Activity context。

因此在 Activity onCreate 中创建适配器，将 Activity 作为上下文传递，并在接收消息时将新数据传递给旧适配器(不要创建新适配器)