通过FragmentStateAdapter将数据从Activity传递到Fragment

问题描述 投票：0回答：2

我目前正在开发一个评分助手应用程序的个人项目应用程序。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精美功能。

现在，我有一个使用 

ViewPager2
的选项卡式活动。对于熟悉它的人来说，您会比我了解更多，但我注意到我从未在活动中实例化我的 
Fragment
类，仅在 
FragmentStateAdapter
中实例化。在我的活动中，我只使用两个选项卡，一个用于游戏方面，一个用于分数显示。考虑到这一点，我的活动课程如下所示：

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。当我有意开始此活动时，我会传递正在玩的游戏的 
ID
。这就是我遇到问题的地方。

我想做的事：

我想将从 

gameID
获得的变量 
intent.getLongExtra("GameID", 0)
一直传递到 
EightHoleScoresFragment
类。

我没有使用 

Bundle
和 
putParcelableArrayList()

这是我使用的其他类。 请注意，类 Participant.java 是我想要使用 

gameID
变量提取的内容。

参与者.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;
    }
}

对于代码的摘要量，我深表歉意。我觉得有必要了解正在发生的事情。正如我所说，我尝试使用 

Bundle
，遵循网站上的各种答案，但没有一个有效。我想知道是否有可能通过链接回父母
EightHoleScoresFragment
的方法直接将意图的内容传递给
EightHoleActivity
，但我不确定......

提前致谢！

java android android-fragments android-activity bundle
2个回答
4
投票

请尝试这个方法

活动中：

将 gameId 作为额外参数传递并在适配器中接收

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：

以这种方式接收片段中的 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);
    }
}
0
投票

我知道这是 3 年前的事了，所以你可能已经明白了……但是有一种简单得多的方法可以做到这一点。 Rajasekhar 的答案当然是“正确”的方法......但也可以不陷入捆绑和争论。

EightHoleActivity.java 这会将变量获取到您的适配器中。

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

EightHolePagerAdapter 一旦进入您的适配器...该变量即可用于您的所有片段。

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.sendVariable(gameId);
        }
    }

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

EightHoleScoresFragment 此时您所要做的就是设置一个静态变量，然后就完成了。您不需要创建捆绑包或从该捆绑包中检索，因为数据已经存在。

public class EightHoleScoresFragment extends Fragment {

    private static final String ARG_GAME_ID = "game_id";
    static long gameId2;

    public static EightHoleScoresFragment sendVariable(long gameId) {
        EightHoleScoresFragment fragment = new EightHoleScoresFragment();
        gameId2 = gameId;
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
    }

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

        Log.d("EightHoleScoresFragment", "Game Id = " + gameId2);
    }
}

现在就完成了。不需要捆绑包或参数。少了几行代码。我想说，拥有一个捆绑包对于将分数移动到其他地方很有用...但是只要您只需将数据从活动移动到片段，那么...一旦它位于适配器中...您就完成了。 :)

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