如何将所有子项及其值添加到ListView（Firebase数据库）

Question

我正在写这篇文章，因为我被困住了，我是Firebase的新手，我不知道从这里去哪里。

我已经尝试过stackoverflow的多种解决方案，但是没有任何效果。

这是我的代码：

public class HistoryActivity extends AppCompatActivity  {

ArrayAdapter<String> adapter;
ListView listView;
DatabaseReference mDatabase;
FirebaseAuth mAuth;
List<String> itemList;

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

    itemList = new ArrayList<>();
    listView = findViewById(R.id.listScore);

    mAuth = FirebaseAuth.getInstance();
    mDatabase = FirebaseDatabase.getInstance().getReference("scores/" + mAuth.getUid() + "/game1");

    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            itemList.clear();

                Score score = dataSnapshot.getValue(Score.class);
                String gameInformation = "Date: " + score.getDate() + ", Time: " + score.getTime() + ". \nYou've chosen " + score.getCat1() + " as your range, " + score.getCat2() + " as sign of your equations and the time was " + score.getCat3() + ".\nYour score was " + score.getScore();
                itemList.add(gameInformation);

                Log.d("Test", score.getDate());                      

                adapter = new ArrayAdapter<String>(HistoryActivity.this,android.R.layout.simple_list_item_1, itemList);
                listView.setAdapter(adapter);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
 }

我的数据库如下所示：

我的数据库所有这些都在起作用，但是我不知道如何显示所有游戏细节，而不仅仅是第一个，所以我将不胜感激。

Edit1：应用了for循环的建议后，出现以下错误：

致命异常

我认为我的数据库引用是错误的，但是我尝试了几种方法，但仍然无法正常工作...

这是我的分数课：

public class Score {

private String cat1;
private String cat2;
private String cat3;
private String date;
private String time;
private String score;
private Long gameCount;

public Score() { }

public Score(String cat1, String cat2, String cat3, String date, String time, String score, Long gameCount) {

    this.cat1 = cat1;
    this.cat2 = cat2;
    this.cat3 = cat3;
    this.date = date;
    this.time = time;
    this.score = score;
    this.gameCount = gameCount;
}

public String getCat1() {
    return cat1;
}

public void setCat1(String cat1) {
    this.cat1 = cat1;
}

public String getCat2() {
    return cat2;
}

public void setCat2(String cat2) {
    this.cat2 = cat2;
}

public String getCat3() {
    return cat3;
}

public void setCat3(String cat3) {
    this.cat3 = cat3;
}

public String getDate() {
    return date;
}

public void setDate(String date) {
    this.date = date;
}

public String getTime() {
    return time;
}

public void setTime(String time) {
    this.time = time;
}

public String getScore() {
    return score;
}

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

public Long getGameCount() {
    return gameCount;
}

public void setGameCount(Long gameCount) {
    this.gameCount = gameCount;
}

Edit2：应用新的数据库引用后，我得到空值，并且在控制台中得到以下错误：

没有二传手的消息

Answer 1

1.）从快照中获取所有子级

2.）将所有这些添加到列表中

3.）使用列表使用适配器填充listview。

mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            itemList.clear();
            // 1
            for (DataSnapshot ds : dataSnapshot.getChildren()) {
                    Score score = ds.getValue(Score.class);
            // 2
                    itemList.add("Date: " + score.getDate() + ", Time: " + score.getTime() + ". \nYou've chosen " + score.getCat1() + " as your range, " + score.getCat2() + " as sign of your equations and the time was " + score.getCat3() + ".\nYour score was " + score.getScore());
                }
            // 3
            adapter = new ArrayAdapter<String>(HistoryActivity.this,android.R.layout.simple_list_item_1, itemList);
            listView.setAdapter(adapter);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

尽管我强烈建议使用自定义适配器而不是阵列适配器

更新：要获取所有子项，datasnapshot引用的路径应指向root而不是特定的子项，因此请使用

mDatabase = FirebaseDatabase.getInstance().getReference("scores");

Answer 2

你必须稍微改变一下onDataChange()

mDatabase.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
   if(dataSnapshot.exists())
   itemList.clear();
            {
                for(DataSnapshot postSnapShot : dataSnapshot.getChildren())
                {
                    Score score = postSnapShot.getValue(Score.class);
            String gameInformation = "Date: " + score.getDate() + ", Time: " + score.getTime() + ". \nYou've chosen " + score.getCat1() + " as your range, " + score.getCat2() + " as sign of your equations and the time was " + score.getCat3() + ".\nYour score was " + score.getScore();
            itemList.add(gameInformation);

            Log.d("Test", score.getDate());  
                }
            }

            adapter = new ArrayAdapter<String>(HistoryActivity.this,android.R.layout.simple_list_item_1, itemList);
            listView.setAdapter(adapter);
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {

    }
});