android - recyclerview 列表未显示在 android 中

Question

这个问题在这里已经有了答案:





What is a NullPointerException, and how do I fix it?

(12 个回答)


12 个月前关闭。




嗨，在下面的代码中，我正在向 account_name 添加值，然后使用该适配器执行 set adapter.response 来服务器，但值没有添加到列表中，并且列表也在显示。

用于显示使用 recyclerview 来显示值。

任何人都可以帮助我哪里出错了

错误:

java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.LayoutInflater.inflate(int, android.view.ViewGroup, boolean)' on a null object reference
        at com.genworks.oppm.Adapter.MyAdapter.onCreateViewHolder(MyAdapter.java:32)
        at com.genworks.oppm.Adapter.MyAdapter.onCreateViewHolder(MyAdapter.java:19)

更新代码:

Activity .java:

for(SyncBlocks syncBlocks1:syncBlocks){

                        String label=syncBlocks1.getLabel();

                        ArrayList<SynFields> synFields=syncBlocks1.getFields();

                        ArrayList<SynFields> jsonArray=syncBlocks1.getFields();

                        for(SynFields synFields1:synFields){

                            String name=synFields1.getName();

                            Object values = synFields1.getValue().toString();

                            try {

                                if (values instanceof JSONObject) {
                                    JSONObject jsonObject1 = new
                                            JSONObject(String.valueOf(synFields1.getValue()));
                                    String value=jsonObject1.getString("value");
                                }else if (values instanceof String) {
                                    //here, you get string

                                     String value =  synFields1.getValue().toString();
                                    //account_name.addAll(value);
                                    String value_names= String.valueOf(synFields1.getValue());
                                   // Log.e("account_name", String.valueOf(account_name.add(value)));
                                    account_name.add(value_names);

                                    //account_name.add(value);

                                }

                            } catch (JSONException e) {
                                e.printStackTrace();
                            }

                        }

                        myAdapter = new MyAdapter(getContext(),account_name);
                        recyclerView.setLayoutManager(new LinearLayoutManager(getContext(), LinearLayoutManager.VERTICAL, false));
                        recyclerView.setAdapter(myAdapter);

                    }

MyAdapter.java:

   public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    private LayoutInflater inflater;
    private Context mContext;
    private ArrayList<String> mSynFields=new ArrayList<>();

    public MyAdapter(Context context, ArrayList<String> synFieldsArrayList) {
        mContext=context;
        mSynFields=synFieldsArrayList;
    }
    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View view = inflater.inflate(R.layout.fragment_account, parent, false);
        MyViewHolder holder = new MyViewHolder(view);

        return holder;
    }

    @Override
    public void onBindViewHolder(MyViewHolder holder, int position) {

       holder.name.setText(mSynFields.get(position));


    }

    @Override
    public int getItemCount() {

        return mSynFields.size();
    }

    class MyViewHolder extends RecyclerView.ViewHolder{

        TextView country, name, city;
        ImageView iv;

        public MyViewHolder(View itemView) {
            super(itemView);

            country = (TextView) itemView.findViewById(R.id.headingText);
            name = (TextView) itemView.findViewById(R.id.subHeaderText);
            city = (TextView) itemView.findViewById(R.id.subHeadingText);
        }

    }
}

Answer 1

您收到此错误是因为您调用了 inflate来自 null 的方法引用( inflater )。

您必须初始化您的 inflater像下面。

@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        inflater = LayoutInflater.from(parent.getContext()); // add this line.

        //or you can do like below
        // View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fragment_account, parent, false);

        View view = inflater.inflate(R.layout.fragment_account, parent, false);

        MyViewHolder holder = new MyViewHolder(view);

        return holder;
    }