java - 如何从另一个数组中存在的值创建数组

Question

我有一个小问题无法解决:我有一个从 API 获取的对象数组(国家/地区)。每个对象中的参数之一(国家/地区)是一个边界国家/地区 - 值名称 = 边界的数组。在一个 fragment 中，我显示了从 API 获取的所有国家/地区。我的目标之一是单击某个国家/地区，然后打开一个新屏幕，其中将显示与我单击的国家/地区接壤的所有国家/地区。

我已经拥有在屏幕之间切换的所有逻辑，两个屏幕上的 RecyclerViews 等等，但我不知道如何创建和解析新屏幕上的接壤国家/地区的新数组。

这就是我现在所拥有的:

所有国家/地区适配器:

public class CountryAdapter extends RecyclerView.Adapter<CountryAdapter.CountryViewHolder> {


    @Override
    public void onBindViewHolder(@NonNull CountryViewHolder holder, final int position) {
        holder.mTVCountryName.setText(countries.get(position).getName());
        holder.mTVCountryNativeName.setText(countries.get(position).getNativeName());

        GlideToVectorYou
                .init()
                .with(mContext)
                .load(Uri.parse(countries.get(position).getFlag()), holder.mCountryFlag);

        holder.mCountryFlag.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {


                if (iOnItemClickListener != null) {
                    //Array list of all border countries by alpha3 value
                    List<String> borderCountriesAlpha3 = new ArrayList<>();
                    for (int i = 0; i < countries.get(position).getBorders().size(); i++) {
                        try {
                            borderCountriesAlpha3.add(countries.get(position).getBorders().get(i));
                        } catch (Exception e) {

                        }
                    }
                    iOnItemClickListener.onItemClick(position, borderCountriesAlpha3);
                }
            }
        });
    }

从API获取数据:

public void getAllCountries(){
        ApiService apiService = ApiClient.getRetrofitInstance().create(ApiService.class);
        call = apiService.getAllCountries();
        call.enqueue(new Callback<List<Country>>() {
            @Override
            public void onResponse(Call<List<Country>> call, Response<List<Country>> response) {
                mCountryPresenter.generateDataList(response.body());
            }

            @Override
            public void onFailure(Call<List<Country>> call, Throwable t) {

            }
        });
    }

国家 pojo 类:

public class Country implements Comparable<Country> {

    @SerializedName("name")
    @Expose
    private String name;
    @SerializedName("alpha3Code")
    @Expose
    private String alpha3Code;
    @SerializedName("borders")
    @Expose
    private List<String> borders = null;
    @SerializedName("nativeName")
    @Expose
    private String nativeName;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAlpha3Code() {
        return alpha3Code;
    }

    public void setAlpha3Code(String alpha3Code) {
        this.alpha3Code = alpha3Code;
    }


    public List<String> getBorders() {
        return borders;
    }

    public void setBorders(List<String> borders) {
        this.borders = borders;
    }

    public String getNativeName() {
        return nativeName;
    }

    public void setNativeName(String nativeName) {
        this.nativeName = nativeName;
    }
}

包含所有国家/地区回收商 View 的 fragment :

public class CountryListFragment extends Fragment implements CountryPresenter {

    private View view;
    private RecyclerView mRVCountries;
    private CountryAdapter mCountryAdapter;
    private CountriesView mCountriesView;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.fragment_country_list, container, false);
        initView(view);
        initClasses();
        initContentView();
        return view;
    }

    private void initClasses() {
        mCountriesView = new CountriesView(this, getContext());
    }

    private void initView(View view) {
        mRVCountries = view.findViewById(R.id.rvCountries);
    }

    private void initContentView() {
        mCountriesView.getAllCountries();
    }

    @Override
    public void generateDataList(List<Country> countries) {
        mCountryAdapter = new CountryAdapter(countries, getContext(), getActivity());
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getContext());
        mRVCountries.setLayoutManager(layoutManager);
        mRVCountries.setAdapter(mCountryAdapter);

        mCountryAdapter.setiOnItemClickListener(new CountryAdapter.OnItemClickListener() {
            @Override
            public void onItemClick(int position, List<String> borderCountries) {
                Log.d("myDebug", "onItemClick: " + position + " " + borderCountries);

            }
        });
    }

    public void sortByNativeName() {
        mCountryAdapter.sortByNativeName();
    }

    public void sortByArea() {
        mCountryAdapter.sortByArea();
    }

}

Answer 1

您可以使用Java的流API或Collections API来搜索列表、将子列表复制到另一个列表等。以下是您要求查找给定国家/地区的边界国家/地区并丢失边界国家/地区对象的示例-

package com.advisory.pic.etl.claim.standardize;

import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

public class Test {

    public static void main(String[] args) {      

    }

    public void workOnCountries(){
        List<Country> countries = Arrays.asList(new Country("United States","USA",Arrays.asList("MXO","CDA")),
                new Country("Mexico","MXO",Arrays.asList("USA","CLB")),
                new Country("Colombia","CLB",Arrays.asList("MXO","VNZ")),
                new Country("Canada","CNA",Arrays.asList("USA")));

        //get list of neighbouring countries for USA
        //first find USA in the list of countries
        Country country = null;
        for(Country c : countries){
            if(c.alpha3Code.equalsIgnoreCase("USA")){
                country = c;
            }
        }

        //find border countries
        List<String> b = country.borders;
        //get border contries from main country list
        List<Country> borderCountries = countries.stream().filter(c -> b.contains(c)).collect(Collectors.toList());        
    }

    private class Country{

        Country(String name, String alpha3Code, List<String> borders){
            this.name = name;
            this.alpha3Code = alpha3Code;
            this.borders = borders;
        }

        private String name;
        private String alpha3Code;
        private List<String> borders = null;
    }
}