Question

数据未添加到列表。该程序从GraphQL服务器获取数据并通过switch语句对其进行过滤，然后将其附加到相应的列表中。但是，如果在switch语句外部访问，则该列表为空。如果在switch语句中打印列表之一，则将正确打印，但是如果在getter函数中打印，则将不会返回任何内容。

这有什么问题？范围？我尝试将初始化放在相同功能或构造函数的几个位置，但结果相同。

package sukebei.anilog.data.source.AniList;

import android.util.Log;

import com.apollographql.apollo.ApolloCall;
import com.apollographql.apollo.ApolloClient;
import com.apollographql.apollo.api.Response;
import com.apollographql.apollo.exception.ApolloException;

import org.jetbrains.annotations.NotNull;

import java.util.ArrayList;
import java.util.List;

import okhttp3.OkHttpClient;

import AniList.UserMediaQuery;
import AniList.UserMediaQuery.Data;
import AniList.type.MediaType;

/*  Data Received Example

[
    Entry {
        __typename = MediaList, 
        progress = 0, 
        progressVolumes = null, 
        score = 0.0, 
        status = PLANNING, 
        notes = null, 
        repeat = 0, 
        media = Media {
            __typename = Media, 
            chapters = null, 
            volumes = null, 
            idMal = 17082, 
            episodes = 12, 
            title = Title {
                __typename = MediaTitle, romaji = Aiura
            }
        }
    }, 
    Entry {
        __typename = MediaList, 
        progress = 0, 
        progressVolumes = null, 
        score = 0.0, 
        status = PLANNING, 
        notes = null, 
        repeat = 0, 
        media = Media {
            __typename = Media, 
            chapters = null, 
            volumes = null, 
            idMal = 33218, 
            episodes = 1, 
            title = Title {
            __typename = MediaTitle, 
            romaji = Kimi no Koe wo Todoketai
            }
        }
    }
]
*/


public class AniList {
    private static final String BASE_URL = "https://graphql.anilist.co";

    private List<UserMediaQuery.Entry> planningMedia = new ArrayList<UserMediaQuery.Entry>();
    private List<UserMediaQuery.Entry> currentMedia = new ArrayList<UserMediaQuery.Entry>();
    private List<UserMediaQuery.Entry> completedMedia = new ArrayList<UserMediaQuery.Entry>();
    private List<UserMediaQuery.Entry> droppedMedia = new ArrayList<UserMediaQuery.Entry>();
    private List<UserMediaQuery.Entry> pausedMedia = new ArrayList<UserMediaQuery.Entry>();
    private List<UserMediaQuery.Entry> repeatingMedia = new ArrayList<UserMediaQuery.Entry>();

    private OkHttpClient okHttpClient;
    private ApolloClient apolloClient;

    public AniList() {
        okHttpClient = new OkHttpClient.Builder().build();
        apolloClient = ApolloClient.builder()
            .serverUrl(BASE_URL)
            .okHttpClient(okHttpClient)
            .build();
    }

    public void loadUserData(String username, MediaType mediaType) {

        UserMediaQuery mediaQuery = UserMediaQuery.builder()
                                        .username(username)
                                        .type(mediaType)
                                        .build();

        apolloClient.query(mediaQuery).enqueue(new ApolloCall.Callback<Data>() {
                @Override public void onResponse(@NotNull Response<Data> dataResponse) {
                    for (UserMediaQuery.List data : dataResponse.data().userMediaList().lists()) {
                        for (UserMediaQuery.Entry entry: data.entries()) {
                            switch(entry.status()) {
                                case PLANNING:
                                    planningMedia.add(entry);
                                    break;
                                case CURRENT:
                                    currentMedia.add(entry);
                                    break;
                                case COMPLETED:
                                    completedMedia.add(entry);
                                    break;
                                case DROPPED:
                                    droppedMedia.add(entry);
                                    break;
                                case PAUSED:
                                    pausedMedia.add(entry);
                                    break;
                                case REPEATING:
                                    repeatingMedia.add(entry);
                                    break;
                            }
                        }
                    }
                }

                @Override
                public void onFailure(@NotNull ApolloException t) {
                    Log.e("AniList Source", t.getMessage(), t);
                }
            }
        );
    }

    public List getPlanningMedia() {
        return planningMedia;
    }


    public List getCurrentMedia() {
        return currentMedia;
    }


    public List getCompletedMedia() {
        return completedMedia;
    }


    public List getDroppedMedia() {
        return droppedMedia;
    }


    public List getPausedMedia() {
        return pausedMedia;
    }

    public List getRepeatingMedia() {
        return repeatingMedia;
    }
}

这会打印数据，但是当您在getter函数中打印数据时，它不会打印数据。

            for (UserMediaQuery.List data : dataResponse.data().userMediaList().lists()) {
                for (UserMediaQuery.Entry entry: data.entries()) {
                    if (entry.status() == MediaListStatus.PLANNING) {
                        planningMedia.add(entry);
                        Log.d("planning", planningMedia.toString());
                    }
                }
            }

Answer 1

apolloClient.query(mediaQuery).enqueue以异步方式执行代码，这意味着它使请求入队，因此数组列表将为空，直到请求完成并从另一个线程成功为止。

您可能直接使用getter而不等待回调完成。如果是这种情况，请检查以下可能的解决方案。

如果您正在等待请求完成以在UI上显示某些内容，则可能希望通过使用notifyDataSetChanged()之类的东西将数据再次绑定到UI，例如在RecyclerView的情况下。同样，如果要将这些数据用于其他用途，则应该使用回调机制。

希望这会有所帮助！

数据未添加到list.add

1 个答案: