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Question

我想在UserList中选择displayName show。但我不知道如何在数据库用户中选择displayName你能帮助我吗  例如。我选择6Z86LIYRMaM9vtmOrd23kAeICO63，但我想显示displayName

ListView usersList;
    TextView noUsersText;
    ArrayList<String> al = new ArrayList<>();
    int totalUsers = 0;
    ProgressDialog pd;

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

        usersList = (ListView)findViewById(R.id.usersList);
        noUsersText = (TextView)findViewById(R.id.noUsersText);

        pd = new ProgressDialog(Users.this);
        pd.setMessage("Loading...");
        pd.show();

        String url = "https://chatapp.firebaseio.com/users.json";

        StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener<String>(){
            @Override
            public void onResponse(String s) {
                doOnSuccess(s);
            }
        },new Response.ErrorListener(){
            @Override
            public void onErrorResponse(VolleyError volleyError) {
                System.out.println("" + volleyError);
            }
        });

        RequestQueue rQueue = Volley.newRequestQueue(Users.this);
        rQueue.add(request);

        usersList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                UserDetails.chatWith = al.get(position);
                startActivity(new Intent(Users.this, Chat.class));
            }
        });
    }

    public void doOnSuccess(String s){
        try {
            JSONObject obj = new JSONObject(s);

            Iterator i = obj.keys();
            String key = "";

            while(i.hasNext()){
                key = i.next().toString();

                if(!key.equals(UserDetails.username)) {
                    al.add(key);
                }

                totalUsers++;
            }

        } catch (JSONException e) {
            e.printStackTrace();
        }

        if(totalUsers <=1){
            noUsersText.setVisibility(View.VISIBLE);
            usersList.setVisibility(View.GONE);
        }
        else{
            noUsersText.setVisibility(View.GONE);
            usersList.setVisibility(View.VISIBLE);
            usersList.setAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, al));
        }

        pd.dismiss();
    }

Answer 1

根据评论中的建议，您应该访问firebase文档，了解如何使用SDK。

https://firebase.google.com/docs/database/android/start/

特定于您的问题，您需要为用户创建POJO类，以便稍后在从db中检索用户时序列化对象。

User.java

public class User {
private int avatarId;
private String connection;
private Long createAt;
private String displayName;
private String email;

public User() {
}

public int getAvatarId() {
    return avatarId;
}

public void setAvatarId(int avatarId) {
    this.avatarId = avatarId;
}

public String getConnection() {
    return connection;
}

public void setConnection(String connection) {
    this.connection = connection;
}

public Long getCreateAt() {
    return createAt;
}

public void setCreateAt(Long createAt) {
    this.createAt = createAt;
}

public String getDisplayName() {
    return displayName;
}

public void setDisplayName(String displayName) {
    this.displayName = displayName;
}

public String getEmail() {
    return email;
}

public void setEmail(String email) {
    this.email = email;
}
}

然后你可以像这样从db中获取用户信息。

DatabaseReference databaseRef = FirebaseDatabase.getInstance().getReference()
DatabaseReference userReference = databaseRef.child("users").child("6Z86LIYRMaM9vtmOrd23kAeICO63");
    ValueEventListener userListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        //Create a User POJO class with the same values you have in your db
        //and its getters and setters
        User user = dataSnapshot.getValue(User.class);
        //This is how you get the displayName from a user from the db
        user.getDisplayName();
        // ...
    }

@Override
public void onCancelled(DatabaseError databaseError) {

}
};
userReference.addValueEventListener(userListener);

我希望这会有所帮助