Question

我创建了Firebase登录和注册应用程序！我希望在登录到应用程序后，用户可以从Firebase中检索值。

Firease Database Console

我想在这里显示点数：After Login User can see this page

我使用了此代码但登录到应用程序数据后，它没有返回它。资料活动：

    package com.helploger.www.ezzeearn;

import android.content.Intent;
import android.support.annotation.Nullable;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.ProgressBar;
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.ValueEventListener;

import java.util.Map;

public class ProfileActivity extends AppCompatActivity implements View.OnClickListener {

    Toolbar toolbar;


    //firebase auth object
    private FirebaseAuth firebaseAuth;

    //firebase database
    private TextView tv;
    //view objects
    private TextView textViewUserEmail;
    private Button buttonLogout;


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

        //Toolbar

        toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);


        //initializing firebase authentication object
        firebaseAuth = FirebaseAuth.getInstance();



        //if the user is not logged in
        //that means current user will return null
        if (firebaseAuth.getCurrentUser() == null) {
            //closing this activity
            finish();
            //starting login activity
            startActivity(new Intent(this, LoginActivity.class));
        }


        //getting current user
        FirebaseUser user = firebaseAuth.getCurrentUser();
        //initializing views
        textViewUserEmail = (TextView) findViewById(R.id.textViewUserEmail);
        buttonLogout = (Button) findViewById(R.id.buttonLogout);
        tv = (TextView) findViewById(R.id.tv);

        //displaying logged in user name
        textViewUserEmail.setText("Welcome " + user.getEmail());

        //adding listener to button
        buttonLogout.setOnClickListener(this);


    }

    @Override
    protected void onStart() {
        super.onStart();
        DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
        DatabaseReference ezzeearnRef = rootRef.child(firebaseAuth.getCurrentUser().getUid());
        ValueEventListener eventListener = new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                String points = dataSnapshot.child("points").getValue(String.class);
               tv.setText(points);
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {}
        };
        ezzeearnRef.addListenerForSingleValueEvent(eventListener);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_logout) {
            firebaseAuth.signOut();
            finish();
            startActivity(new Intent(this, LoginActivity.class));
        }

        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onClick(View view) {
        //if logout is pressed
        if(view == buttonLogout){
            //logging out the user
            firebaseAuth.signOut();
            //closing activity
            finish();
            //starting login activity
            startActivity(new Intent(this, LoginActivity.class));
        }
    }
}

Answer 1

我可以很快看到两个错误：

代码中有"points"，但JSON中有"Points"。大小写很重要，因此您当前的代码会读取不存在的节点。
当您尝试阅读字符串时，您的积分将存储为数字。

所以我认为你会想要：

public void onDataChange(DataSnapshot dataSnapshot) {
   long points = dataSnapshot.child("Points").getValue(Long.class);
   tv.setText(String.valueOf(points));
}

请注意，如果您通过调试器执行代码，则这些类型的问题最容易进行故障排除。在这种情况下，在onDataChange中放置一个断点应该表明它会被触发，这样可以更容易地发现拼写错误。

从Firebase检索用户数据

1 个答案: