java - 构造函数定义为采用 String 但方法调用显示错误 'Array type expected found java.lang.String'

Question

我有一个注册 Activity ，它根据用户选中的复选框对服务器进行异步调用以获取与所选领域相关的技能。我正在使用改造。我定义了一个 SQLQuery 类，其构造函数采用一个 String 参数。现在的问题是，当我使用 String 参数调用构造函数时，它显示错误 Array type expected found java.lang.String。请有人帮我解决这个问题。

提前致谢 这是我的 java 文件

package com.example.vishal.internshipseekerapp;

import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.Toast;

import java.util.HashSet;
import java.util.List;
import java.util.Set;


import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;



public class StudentRegistration extends AppCompatActivity implements View.OnClickListener {

    private final int numFields = 13;
    boolean[] checkField = new boolean[13];
    String[] field = {"computer vision", "content writing", "data mining", "electrical/electronics", "game development", "image processing", "marketing", "mechanical engineering", "mobile app dev", "programming", "software dev", "web dev"};
    Set<Skill> skill = new HashSet<>();

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

        ActionBar ab = getSupportActionBar();
        ab.setDisplayHomeAsUpEnabled(true);

        // register onclick listener for all checkboxes
        ( findViewById(R.id.field0)).setOnClickListener(this);
        ( findViewById(R.id.field1)).setOnClickListener(this);
        ( findViewById(R.id.field2)).setOnClickListener(this);
        ( findViewById(R.id.field3)).setOnClickListener(this);
        ( findViewById(R.id.field4)).setOnClickListener(this);
        ( findViewById(R.id.field5)).setOnClickListener(this);
        ( findViewById(R.id.field6)).setOnClickListener(this);
        ( findViewById(R.id.field7)).setOnClickListener(this);
        ( findViewById(R.id.field8)).setOnClickListener(this);
        ( findViewById(R.id.field9)).setOnClickListener(this);
        ( findViewById(R.id.field10)).setOnClickListener(this);
        ( findViewById(R.id.field11)).setOnClickListener(this);
        //( findViewById(R.id.field12)).setOnClickListener(this);

        // register onclick listener for DONE button
        Button done = (Button) findViewById(R.id.field_select_done);
        done.setOnClickListener(this);
    }

    public void onClick(View v){
        switch(v.getId()){
            case R.id.field0:
                if(((CheckBox) v).isChecked())
                    checkField[0] = true;
            case R.id.field1:
                if(((CheckBox) v).isChecked())
                    checkField[1] = true;
            case R.id.field2:
                if(((CheckBox) v).isChecked())
                    checkField[2] = true;
            case R.id.field3:
                if(((CheckBox) v).isChecked())
                    checkField[3] = true;
            case R.id.field4:
                if(((CheckBox) v).isChecked())
                    checkField[4] = true;
            case R.id.field5:
                if(((CheckBox) v).isChecked())
                    checkField[5] = true;
            case R.id.field6:
                if(((CheckBox) v).isChecked())
                    checkField[6] = true;
            case R.id.field7:
                if(((CheckBox) v).isChecked())
                    checkField[7] = true;
            case R.id.field8:
                if(((CheckBox) v).isChecked())
                    checkField[8] = true;
            case R.id.field9:
                if(((CheckBox) v).isChecked())
                    checkField[9] = true;
            case R.id.field10:
                if(((CheckBox) v).isChecked())
                    checkField[10] = true;
            case R.id.field11:
                if(((CheckBox) v).isChecked())
                    checkField[11] = true;


            case R.id.field_select_done:
                displayRelevantSkills();
        }
    }

    private void displayRelevantSkills() {
        String field = "field";
        String checkBoxName;


        final String SKILL_FIELD_URL = "https://data.outfight74.hasura-app.io/";


//        OkHttpClient.Builder httpClient = new OkHttpClient.Builder();

        // set request options for all requests
        Retrofit.Builder builder =
                new Retrofit.Builder()
                        .baseUrl(SKILL_FIELD_URL)
                        .addConverterFactory(
                                GsonConverterFactory.create()
                        );

        // create retrofit adapter
        Retrofit retrofit =
                builder
                    /*.client(
                            httpClient.build()
                    )*/
                    .build();

        // create retrofit REST client
        getRelevantSkills skillClient =  retrofit.create(getRelevantSkills.class);

        // for each checkbox do
        for(int i = 0; i < numFields; i++) {
            // if checkbox is ticked
            if(checkField[i]) {
                // fetch relevant skills from server
                SQLQuery skillQuery = new SQLQuery(field[i]);

                Call<List<Skill>> call =
                        skillClient.relevantSkills(skillQuery);

                // Execute the call asynchronously. Get a positive or negative callback.
                call.enqueue(new Callback<List<Skill>>() {
                    @Override
                    public void onResponse(Call<List<Skill>> call, Response<List<Skill>> response) {
                        // The network call was a success and we got a response
                        // add to skills HashSet
                        skill.addAll(response.body());
                        Toast.makeText(getApplicationContext(), "Success", Toast.LENGTH_SHORT).show();
                    }

                    @Override
                    public void onFailure(Call<List<Skill>> call, Throwable t) {
                        // the network call was a failure
                        // TODO: handle error
                        Toast.makeText(getApplicationContext(), "Error", Toast.LENGTH_SHORT).show();
                    }
                });
            }
        }

        // display a drop down menu having all elements of HashSet
        for(Skill s : skill)
        {
            CheckBox skillItem = new CheckBox(getApplicationContext());
            skillItem.setText(s.getSkill());
        }
    }
}

这是 getRelevantSkills.java 文件

package com.example.vishal.internshipseekerapp;

import java.util.List;

import retrofit2.Call;
import retrofit2.http.Body;
import retrofit2.http.POST;


class Where{
    // this will be given by the user
    private String skill;

    public Where(String skill) {
        this.skill = skill;
    }
}

class Args{
    final String table = "skill_field_relation";
    final String[] columns = {"skill"};
    private Where where;

    public Args(String field) {
        where = new Where(field);
    }
}

class SQLQuery{
    final String type = "select";
    private Args args;
    public SQLQuery(java.lang.String field) {
        args = new Args(field);
    }
}

class Skill{
    private String skill;

    public String getSkill() {
        return skill;
    }

    public Skill(String skill) {
        this.skill = skill;
    }
}

public interface getRelevantSkills {
    @POST("/v1/query")
    Call<List<Skill>> relevantSkills(
            @Body SQLQuery fetchSkills
    );
}

Answer 1

您正在尝试将 field[i] 传递给 SQLQuery 构造函数，但是 field 是一个 String ，不是数组。您应该改为传递 field。

编辑:

private void displayRelevantSkills() {
    String field = "field";

    ...

    SQLQuery skillQuery = new SQLQuery(field[i]);
    ...
}

你有一个 String 类型的局部 field 变量，它隐藏了同名的实例变量(其类型是 String[]) .

如果你打算使用实例变量(String[] field = {...};)，你应该这样写:

SQLQuery skillQuery = new SQLQuery(this.field[i]);