通过 FragmentStateAdapter 将数据从 Activity 传递到 Fragment

Question

我目前正在为评分助手应用程序开发个人项目应用程序。目的是使用该应用程序跟踪每个玩家的分数，并获得高分和其他花哨的功能。

现在，我有一个使用 ViewPager2 的选项卡 Activity。对于那些熟悉它的人来说，你会比我知道的更多，但我注意到我从来没有在 activity 中实例化我的 Fragment classes，只在FragmentStateAdapter。在我的 activity 中，我只使用了两个选项卡，一个用于游戏方面，一个用于点数显示。考虑到这一点，我的 activity class 看起来像这样：

EightHoleActivity.java

package com.example.game;

import android.content.Intent;
import android.os.Bundle;
import com.google.android.material.tabs.TabLayout;
import com.google.android.material.tabs.TabLayoutMediator;
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;

public class EightHoleActivity extends AppCompatActivity {

    private long gameID;
    private RoomDB database;

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

        Intent intent = getIntent();
        gameID = intent.getLongExtra("GameID", 0);
        database = RoomDB.getInstance(EightHoleActivity.this);

        ViewPager2 viewPager2 = findViewById(R.id.eight_hole_view_pager);
        viewPager2.setAdapter(new EightHolePagerAdapter(this));
        TabLayout tabLayout = findViewById(R.id.eight_hole_tabs);
        TabLayoutMediator tabLayoutMediator = new TabLayoutMediator(
                tabLayout, viewPager2, (tab, position) -> {
                    switch (position){
                        case 0: {
                            tab.setText("Current game");
                            tab.setIcon(R.drawable.ic_twotone_games_24);
                            break;
                        }
                        default: {
                            tab.setText("Scores");
                            tab.setIcon(R.drawable.ic_baseline_list_24);
                            break;
                        }
                    }
                }
        );
        tabLayoutMediator.attach();
    }
}

如您所见，我有一个 RoomDatabase 用于在应用程序中存储数据。当我有意开始这个 activity 时，我传递了正在玩的游戏的 ID。这是我遇到问题的地方。

我想做的事情：

我想将从 intent.getLongExtra("GameID", 0) 获得的变量 gameID 一直传递到 EightHoleScoresFragment class.

我没有使用 Bundle 和 putParcelableArrayList()

这是我使用的其他 classes。请注意，class Participants.java 是我要使用 gameID 变量提取的内容。

Participants.java

package com.example.game;

import android.os.Parcel;
import android.os.Parcelable;

import androidx.annotation.Nullable;
import androidx.room.ColumnInfo;
import androidx.room.Entity;
import androidx.room.ForeignKey;
import androidx.room.PrimaryKey;

import java.util.Objects;

@Entity(tableName = "participants", foreignKeys = {
        @ForeignKey(entity = Player.class, parentColumns = "id", childColumns = "player_id", onDelete = ForeignKey.CASCADE),
        @ForeignKey(entity = Game.class, parentColumns = "id", childColumns = "game_id", onDelete = ForeignKey.CASCADE)})
public class Participant implements Parcelable {
    @PrimaryKey(autoGenerate = true)
    private long id;

    @ColumnInfo(name = "player_id", index = true)
    private long playerID;

    @ColumnInfo(name = "game_id", index = true)
    private long gameID;

    @ColumnInfo(name = "score")
    private int score;

    protected Participant(Parcel in) {
        id = in.readLong();
        playerID = in.readLong();
        gameID = in.readLong();
        score = in.readInt();
    }

    public static final Creator<Participant> CREATOR = new Creator<Participant>() {
        @Override
        public Participant createFromParcel(Parcel in) {
            return new Participant(in);
        }

        @Override
        public Participant[] newArray(int size) {
            return new Participant[size];
        }
    };

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public long getPlayerID() {
        return playerID;
    }

    public void setPlayerID(long playerID) {
        this.playerID = playerID;
    }

    public long getGameID() {
        return gameID;
    }

    public void setGameID(long gameID) {
        this.gameID = gameID;
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }

    public Participant(long playerID, long gameID){
        this.playerID = playerID;
        this.gameID = gameID;
    }

    @Override
    public boolean equals(@Nullable Object obj) {
        if (this == obj) return true;
        if (!(obj instanceof Participant)) return false;

        Participant participant = (Participant) obj;
        if (id != participant.id) return false;
        return Objects.equals(score, participant.score) || Objects.equals(playerID, participant.playerID) || Objects.equals(gameID, participant.gameID);
    }

    @Override
    public int hashCode() {
        int result = (int) id;
        result = (int) (31 * result + playerID + gameID + score);
        return result;
    }

    @Override
    public String toString() {
        return "Participant{" +
                "ID=" + id +
                ", PlayerID='" + playerID + '\'' +
                ", GameID='" + gameID + '\'' +
                ", Score='" + score + '\'' +
                '}';
    }

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

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeLong(id);
        dest.writeLong(playerID);
        dest.writeLong(gameID);
        dest.writeInt(score);
    }
}

EightHolePagerAdapter.java

package com.example.game;

import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.fragment.app.FragmentActivity;
import androidx.viewpager2.adapter.FragmentStateAdapter;

public class EightHolePagerAdapter extends FragmentStateAdapter {

    public EightHolePagerAdapter(@NonNull FragmentActivity fragmentActivity) {
        super(fragmentActivity);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        switch (position){
            case 0:
                return new EightHoleGameFragment();
            default:
                return new EightHoleScoresFragment();
        }
    }

    @Override
    public int getItemCount() {
        return 2;
    }
}

EightHoleScoresFragment.java

package com.example.game;

import android.os.Bundle;
import androidx.fragment.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ListView;
import java.util.ArrayList;

public class EightHoleScoresFragment extends Fragment {

    private ArrayList<Participant> participants = new ArrayList<Participant>();

    public EightHoleScoresFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_eight_hole_scores, container, false);
        ListView listView = (ListView) view.findViewById(R.id.eight_hole_current_scores_list);

        ScoresAdapter adapter = new ScoresAdapter(getActivity(), R.layout.scores_adapter_layout, participants);
        listView.setAdapter(adapter);
        return view;
    }
}

对于摘要代码量，我深表歉意。我觉得有必要了解正在发生的事情。我已经按照我所说的那样尝试使用 Bundle，遵循网站上的各种答案，但 none 已经奏效。我想知道是否可以使用一种链接回父 EightHoleActivity 的方法将意图的内容直接传递给 EightHoleScoresFragment 但我不确定...

提前致谢！

Answer 1

请试试这个方法

在Activity中：

将 gameId 作为额外参数传递并在 Adapter 中接收

viewPager2.setAdapter(new EightHolePagerAdapter(this, gameID));

在 ViewPagerAdapter 中：

EightHoleScoresFragment 获取 gameId 并调用片段 newInstance

public class EightHolePagerAdapter extends FragmentStateAdapter {

    private long gameId;

    public EightHolePagerAdapter(@NonNull FragmentActivity fragmentActivity, long gameId) {
        super(fragmentActivity);
        this.gameId = gameId;
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        switch (position){
            case 0:
                return new EightHoleGameFragment();
            default:
                return EightHoleScoresFragment.newInstance(gameId);
        }
    }

    @Override
    public int getItemCount() {
        return 2;
    }
}

在你的片段中：

以这种方式在片段中接收 gameId 参数。

public class EightHoleScoresFragment extends Fragment {

    private static final String ARG_GAME_ID = "game_id";
    private long mGameId;

    public static EightHoleScoresFragment newInstance(long gameId) {
        EightHoleScoresFragment fragment = new EightHoleScoresFragment();
        Bundle args = new Bundle();
        args.putLong(ARG_GAME_ID, gameId);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mGameId = getArguments().getLong(ARG_GAME_ID);
        }
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);

        Log.d("EightHoleScoresFragment", "Game Id = " + mGameId);
    }
}

通过 FragmentStateAdapter 将数据从 Activity 传递到 Fragment

Pass data from Activity to Fragment via FragmentStateAdapter

java

android

bundle

android-fragments

android-activity