在android studio中使用localhost实现API的问题

Question

我正在尝试实现一个简单的 API 来从本地主机读取数据。该 API 在 POSTMAN 中运行良好。但是，当我使用 RETROFIT 实现它时，它不会从本地主机加载数据。我已确保检查网络是否接受来自 80 的响应，情况良好。我还收到了有关 recyclerview 的另一个错误。

这是这两个错误：

1：RecyclerView com.sarmadali.poetryapp E 未连接适配器；跳过布局

另一个是：

java.lang.NullPointerException：尝试在 com.sarmadali.poetryapp.Adapters.PoetryAdapters.getItemCount(PoetryAdapters.java:50) 处的空对象引用上调用虚拟方法“int java.util.ArrayList.size()”

这是我的 MainActivity 代码：

public class MainActivity extends AppCompatActivity {

    RecyclerView recyclerViewPoetry;
    PoetryAdapters poetryAdapters;
    ApiInterfacePoetry apiInterfacePoetry;

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

        InitializationMethod();

 apiInterfacePoetry.getPoetry().enqueue(new Callback<GetPoetryResponse>() {
            @Override
            public void onResponse(Call<GetPoetryResponse> call, Response<GetPoetryResponse> response) {
                try {
                    if (response!=null){
                        if (response.body().getStatus().equals("1")){
                            SetAdapter(response.body().getPoetryData());
                        }else {
                            Toast.makeText(MainActivity.this, response.body().getMessage(), Toast.LENGTH_SHORT).show();
                        }
                    }
                }catch (Exception e){
                    Log.e("Failure", e.getLocalizedMessage());
                }
            }
            @Override
            public void onFailure(Call<GetPoetryResponse> call, Throwable t) {
                Log.e("Failure Failure", t.getLocalizedMessage());
                Toast.makeText(MainActivity.this, "Something went wrong", Toast.LENGTH_SHORT).show();
            }
        });
    }

 private void InitializationMethod(){

        recyclerViewPoetry = findViewById(R.id.recyclerViewPoetry);

        //initializing apis
        Retrofit retrofit = ApiClient.getClient();
        apiInterfacePoetry = retrofit.create(ApiInterfacePoetry.class);
//        poetryModelArrayList = new ArrayList<>();
    }

    private void SetAdapter(ArrayList<PoetryModel> poetryLists){

        poetryAdapters = new PoetryAdapters(this, poetryLists);
        //set layout manager
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        recyclerViewPoetry.setLayoutManager(linearLayoutManager);

        recyclerViewPoetry.setAdapter(poetryAdapters);

    }
}

ApiClient.java

public class ApiClient {

    public static Retrofit retrofit=null;

    public  static Retrofit getClient(){

        if (retrofit==null) {

            OkHttpClient okHttpClient = new OkHttpClient.Builder().build();
            Gson gson = new GsonBuilder().create();

            retrofit = new Retrofit.Builder()
                    .baseUrl("http://192.168.10.7/PHPPoetryApis/")
                    .client(okHttpClient)
                    .addConverterFactory(GsonConverterFactory.create(gson))
                    .build();
        }
        return retrofit;
    }
}

PoetryAdapters.java

public class PoetryAdapters extends RecyclerView.Adapter<PoetryAdapters.ViewHolderClass>{

    Context context;
    ArrayList<PoetryModel> poetryList;

    //constructor
    public PoetryAdapters(Context context, ArrayList<PoetryModel> poetryModels) {
        this.context = context;
        this.poetryList = poetryModels;
    }

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

        //inflating the layout
        View view = LayoutInflater.from(context).inflate(R.layout.poetry_list_view_design, null);
        return new ViewHolderClass(view);
    }

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

        //set all the data

        holder.poetName.setText(poetryList.get(position).getP_Name());
        holder.p_Poetry.setText(poetryList.get(position).getPoetry());
        holder.dateTime.setText(poetryList.get(position).getDate_Time());
    }

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



    //viewholder class created
    public class ViewHolderClass extends RecyclerView.ViewHolder{

        TextView poetName, p_Poetry, dateTime;
        Button btnUpdatePoetry, btnDeletePoetry;
        public ViewHolderClass(@NonNull View itemView) {
            super(itemView);

            poetName = itemView.findViewById(R.id.textPoetName);
            p_Poetry = itemView.findViewById(R.id.textPoetry);
            dateTime = itemView.findViewById(R.id.textDatenTime);

            btnUpdatePoetry = itemView.findViewById(R.id.buttonUpdate);
            btnDeletePoetry = itemView.findViewById(R.id.buttonDelete);
        }
    }

}

已更新

入队方法的改变：

apiInterfacePoetry.getPoetry().enqueue(new Callback<GetPoetryResponse>() {
            @Override
            public void onResponse(Call<GetPoetryResponse> call, Response<GetPoetryResponse> response) {

                try {

                    if (response.isSuccessful() && response.body() != null) {
                        if (response.body().getStatus().equals("1")) {
                            Log.e("Status Poetry", response.body().getStatus());

                            ArrayList<PoetryModel> poetryData = response.body().getPoetryData();
                            if (poetryData != null) {
                                SetAdapter(poetryData);
                            } else {
                                Toast.makeText(MainActivity.this, "Poetry data is null", Toast.LENGTH_SHORT).show();
                            }
                        } else {
                            Toast.makeText(MainActivity.this, response.body().getMessage(), Toast.LENGTH_SHORT).show();
                        }
                        Toast.makeText(MainActivity.this, response.body().getMessage(), Toast.LENGTH_SHORT).show();
                    } else {
                        Toast.makeText(MainActivity.this, "API call was not successful", Toast.LENGTH_SHORT).show();
                    }
                }catch (Exception e){
                    Log.e("Failure", e.getLocalizedMessage());
                }
            }

            @Override
            public void onFailure(Call<GetPoetryResponse> call, Throwable t) {
                Log.e("Failure Failure", t.getLocalizedMessage());
                Toast.makeText(MainActivity.this, "Something went wrong", Toast.LENGTH_SHORT).show();
            }
        });

这里第一次检查成功，toast 响应为 API 中设置的“记录可用”

if (response.isSuccessful() && response.body() != null)

第二个是

if (response.body().getStatus().equals("1")) 它还在日志中返回 1 表示记录可用。

还有这个

诗歌数据！= null

为 null，因为返回 null。

response.body().getPoetryData()

我认为这里没有任何网络相关问题。

我希望这有助于回答我的问题。

Answer 1

我通过比较 API 响应 JSON 的结构和 GetPoetryResponse 类的结构意识到了这一点。类结构与 JSON 结构（包括字段名称和层次结构）不匹配。这些不匹配导致 Gson 无法正确反序列化 JSON，因此我从 GetPoetryResponse() 收到 null 异常。现在一切都按顺序进行了。