Question

我正在尝试使用listView在排行榜上显示我的用户的分数。由于某种原因，我只能获取第一个用户的电子邮件和分数，而我不确定如何让其余用户显示在屏幕上。

也许它们没有被添加到列表视图中，或者循环是错误的？

package com.example.securityapp;

import androidx.appcompat.app.AppCompatActivity;

import android.nfc.Tag;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.google.firebase.database.ValueEventListener;

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

import static java.lang.System.in;

public class leaderboard extends AppCompatActivity {

    DatabaseReference databaseUsers;
    FirebaseDatabase database = FirebaseDatabase.getInstance();
    FirebaseAuth mAuth;
    private static final String TAG = "leaderboard";
    String s;
    ListView listView;
    ArrayList list;
    ArrayAdapter<String> arrayAdapter;


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

        mAuth = FirebaseAuth.getInstance();
        FirebaseUser user = mAuth.getCurrentUser();
        listView = (ListView) findViewById(R.id.list);
        list = new ArrayList<String>();
        arrayAdapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout., list);



        leaderBoard();




    }

    public void leaderBoard(){
        database.getReference().child("Scores").addValueEventListener(new ValueEventListener() {
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    System.out.println("The score is: " + snapshot.child("Points").getValue());
                    s = s + snapshot.child("Username").getValue() + "         " + snapshot.child("Points").getValue() + "\n";
                    list.add(s);
                    listView.setAdapter(arrayAdapter);
                    arrayAdapter.notifyDataSetChanged();

                }

            }


            @Override
            public void onCancelled(DatabaseError databaseError) {
                // Getting Post failed, log a message
                Log.w(TAG, "loadPost:onCancelled", databaseError.toException());

            }


        });

    }


}

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content">


    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        tools:context=".leaderboard">

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="0.38">

            <TextView
                android:layout_width="420dp"
                android:layout_height="150dp"
                android:gravity="center"
                android:text="Leaderboard!"
                android:textAppearance="@style/TextAppearance.AppCompat.Body1"
                android:textColor="#0C40F1"
                android:textSize="50dp"
                android:textStyle="bold">

            </TextView>
        </RelativeLayout>

        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="0.38">
            <LinearLayout
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_centerHorizontal="true"
                android:layout_weight="1"
                android:weightSum="2">

                <TextView
                    android:layout_height="wrap_content"
                    android:layout_width="wrap_content"
                    android:text="Points"
                    android:layout_gravity="left"
                    android:textSize="20dp"
                    />

            </LinearLayout>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:gravity="right"
                android:text="User"
                android:textSize="20dp">

            </TextView>
        </RelativeLayout>
        <RelativeLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="0.38">

            <ListView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/list">

            </ListView>


        </RelativeLayout>


    </LinearLayout>



</ScrollView>

Answer 1

您正在将适配器设置为for循环

替换

for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    System.out.println("The score is: " + snapshot.child("Points").getValue());
                    s = snapshot.child("Username").getValue() + "         " + snapshot.child("Points").getValue() + "\n";
                    list.add(s);
                    listView.setAdapter(arrayAdapter);
                    arrayAdapter.notifyDataSetChanged();

                }

与

if(dataSnapshot.exist()){
     list = new ArrayList<String>();
     for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        System.out.println("The score is: " + snapshot.child("Points").getValue());
                       String s =  snapshot.child("Username").getValue() + "         " + snapshot.child("Points").getValue() + "\n";
                        list.add(s); 
                    }
    arrayAdapter = new ArrayAdapter<>(getApplicationContext(), android.R.layout., list);
    listView.setAdapter(arrayAdapter);

    }

在调用addvalue事件侦听器（侦听实时更改）时，您必须在数据发生更改时初始化列表并在循环中声明“ s”。

使用ListView制作排行榜

1 个答案: