从 SQLite 获取数据并显示到 RecyclerView

Question

大家好， 我正在尝试为我的公司构建一个应用程序。我已将数据存储到 SQLite 中。在搜索界面中，我可以从数据库中搜索并在简单的 TextView 上查找结果。但我想通过使用 RecyclerView 查看实际结果。我在这里附上了我的代码和适配器类。 问题是我无法在 RecyclerView 中查看查询数据。请帮我做这件事。

1. MainActivity.java

public class Client extends AppCompatActivity {

    private static final String TAG = Client.class.getSimpleName();
    ClientDatabase db;
    ClientModel clientModel;
    RequestQueue requestQueue;
    Context context;
    Button search_button;
    EditText search_word;
    TextView search_result;
    RecyclerView recycler_view;
    FinalAdapter adapter;
    ArrayList<ClientModel> clients = new ArrayList<>();

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

        db = new ClientDatabase(this);

        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        search_word = (EditText)findViewById(R.id.search_word);
        search_result = (TextView)findViewById(R.id.search_result);
        search_button = (Button)findViewById(R.id.search_button);

        search_button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showResult(v);

            }
        });

        RequestData();
    }

        private void RequestData() {
    Log.d(TAG, "RequestData: Requesting Data from API");
    RequestQueue requestQueue = Volley.newRequestQueue(getApplicationContext());
    String url = getResources().getString(R.string.url);
    JSONObject jsonObject = new JSONObject();
    JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.GET, url, null, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            try {
                JSONArray info = response.getJSONArray("response");
                ClientDatabase clientDatabase = new ClientDatabase(getApplicationContext());
                Log.d(TAG, "onResponse: Inserting data into Database");

                for (int i =0; i<info.length(); i++){
                    JSONObject jsonObject = info.getJSONObject(i);
                    ClientModel clientModel = new ClientModel();
                    clientModel.setClient_name(jsonObject.getString("client_name"));
                    clientModel.setAddress(jsonObject.getString("address"));
                    clientModel.setNote(jsonObject.getString("note"));
                    clientModel.setCp_name(jsonObject.getString("cp_name"));
                    clientModel.setCp_phone(jsonObject.getString("cp_phone"));
                    clientModel.setCp_email(jsonObject.getString("cp_email"));
                    clientModel.setAssign_person_name(jsonObject.getString("assign_person_name"));
                    clientDatabase.AddClient(clientModel);
                    clients.add(clientModel);
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Toast.makeText(getApplicationContext(), "Error in saving",Toast.LENGTH_LONG).show();
        }
    });
    requestQueue.add(jsonObjectRequest);
}

    private void _All() {
        Log.d(TAG, "_All: Clients in ready");
        Cursor cursor = db.ViewData();

    }

    private void showResult(View view){
        try {

            String word = search_word.getText().toString();
            search_result.setText("Result for : " + word + ":\n\n");

            //search for word in the database
            Cursor cursor = db.search(word);

            cursor.moveToFirst();

            if (cursor != null && cursor.getCount() > 0){
                int index1, index2, index3, index4;
                String result;
                do {
                    // Don't guess at the column index. Get the index for the named column.
                    index1 = cursor.getColumnIndex(db.COLUMN_CLIENT_NAME);
                    // Get the value from the column for the current cursor.
                    result = cursor.getString(index1);
                    // Add result to what's already in the text view.
                    search_result.append(result + "\n");
                } while (cursor.moveToNext());
                cursor.close();
            } else {
                search_result.append(getString(R.string.no_result));
            }

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

    private void initRecyclear(){
        recycler_view = (RecyclerView)findViewById(R.id.recycler_view);
        adapter = new FinalAdapter(context, clients);
        recycler_view.setLayoutManager(new LinearLayoutManager(this));
        recycler_view.setAdapter(adapter);
    }

    @Override
    protected void onDestroy() {
        db.RemoveData();
        super.onDestroy();
    }
}

1. FinalAdapter.java

public class FinalAdapter extends RecyclerView.Adapter<FinalAdapter.ViewHolder> {

    Context context;
    ArrayList<ClientModel> clientModelList;

    public FinalAdapter(Context context, ArrayList<ClientModel> clientModelList) {
        this.context = context;
        this.clientModelList = clientModelList;
    }

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

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

        holder.name.setText(clientModelList.get(position).getClient_name());
        holder.phone.setText(clientModelList.get(position).getCp_phone());
        holder.email.setText(clientModelList.get(position).getCp_email());
        holder.assigned.setText(clientModelList.get(position).getAssign_person_name());
    }

    @Override
    public int getItemCount() {
        return 0;
    }

    class ViewHolder extends RecyclerView.ViewHolder {

        TextView name, phone, email, assigned;

        public ViewHolder(View itemView) {
            super(itemView);
            name = (TextView) itemView.findViewById(R.id.client_name);
            phone = (TextView) itemView.findViewById(R.id.client_phone);
            email = (TextView) itemView.findViewById(R.id.client_email);
            assigned = (TextView) itemView.findViewById(R.id.assign_name);
        }
    }
}

1. 截图

Answer 1

你错过了两点：

1. 在 onCreate 块内启动 initRecyclear()
2. 填充您的clients ArrayList

解决方案

从onCreate()方法调用initRecyclear()：

initRecylear();
search_button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            showResult(v);

        }
    });

然后在 RequestData() 方法中填充您的客户列表

 private void RequestData() {

    ClientModel cmObj = new ClientModel();
    //Here Fetch your Data and put it to ClientModel object cmObj then add this object into your clients ArrayList
    clients.add(cmObj);
    //After Completion on data preparation call below method to notify your recycler 
    adapter.notifyDataSetChanged();
}

终于从onClick事件调用RequestData()方法

search_button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            RequestData();

        }
    });