Question

package com.example.demo.myblog;

import android.content.Context;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.squareup.picasso.Picasso;

import org.w3c.dom.Text;

public class MainActivity extends AppCompatActivity {

    private RecyclerView mReclBlogMainList; //The main recycler view for listing posts
    private DatabaseReference mDatabaseRef;
    private FirebaseAuth mAuth;
    private FirebaseAuth.AuthStateListener mAuthStateListener;

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

        mAuth = FirebaseAuth.getInstance();
        mAuthStateListener = new FirebaseAuth.AuthStateListener() {
            @Override
            public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
                if(firebaseAuth.getCurrentUser() == null){
                    Toast.makeText(MainActivity.this, "User null", Toast.LENGTH_SHORT).show();
//                    startActivity(new Intent(MainActivity.this, LoginActivity.class));
//                    finish(); //can't go back to previous activity # MainActivity
                }
            }
        };

        //All our posts reside inside the Blog directory under the database root
        mDatabaseRef = FirebaseDatabase.getInstance().getReference().child("Blog");

        //Initialize Recycler View
        mReclBlogMainList = (RecyclerView)findViewById(R.id.reclBlogMainList);
        mReclBlogMainList.setHasFixedSize(true);
        //setting a layout manager for recycler view -- vertical list
        mReclBlogMainList.setLayoutManager(new LinearLayoutManager(this));
    }

    @Override
    protected void onStart() {
        super.onStart();
        //adding auth state listener
        mAuth.addAuthStateListener(mAuthStateListener);
        //Creating adapter after creating view holder class below
        FirebaseRecyclerAdapter<Blog, BlogViewHolder>firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<Blog, BlogViewHolder>(
                Blog.class,
                R.layout.blog_row,
                BlogViewHolder.class,
                mDatabaseRef
        ) {
            @Override
            protected void populateViewHolder(BlogViewHolder viewHolder, Blog model, int position) {
                //setting title, desc, image to view holder after fetch from database
                viewHolder.setTitle(model.getTitle());
                viewHolder.setDesc(model.getDesc());
                viewHolder.setImage(getApplicationContext(), model.getImage()); //since View holder is static class
            }
        };
        //setting up recycler view with firebase adapter
        mReclBlogMainList.setAdapter(firebaseRecyclerAdapter);
    }

    //inflate the menu created in the main_menu file
    // onto the top menu bar of the app
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        //called when user selects any icon on the inflated menu
        if(item.getItemId() == R.id.action_add){
            // if the user has clicked on the '+' icon
            startActivity(new Intent(MainActivity.this, PostActivity.class));
        }
        return super.onOptionsItemSelected(item);
    }

    //For setting up a recycler view, we need a view holder
    //Creating view holder after setting up Blog class
    public static class BlogViewHolder extends RecyclerView.ViewHolder{
        View mView;
        public BlogViewHolder(View itemView) {
            super(itemView);

            mView = itemView;
        }

        //Set the title and desc for the recycler view posts
        public void setTitle(String title){
            TextView postTitle = (TextView)mView.findViewById(R.id.txtPostTitle);
            postTitle.setText(title);
        }
        public void setDesc(String desc){
            TextView postDesc = (TextView)mView.findViewById(R.id.txtPostDesc);
            postDesc.setText(desc);
        }
        //as it's inside a static class
        public void setImage(Context ctx, String imageUrl){
            ImageView postImage = (ImageView)mView.findViewById(R.id.imgPostImage);

            //with the application context, load the image from
            //the file url into the image view
            Picasso.with(ctx).load(imageUrl).into(postImage);
        }
    }
}

这是一个简单的博客应用程序的主页面。我正在尝试使用AuthStateListener功能中的OnCreate来检查用户是否已登录。但是，当我启动应用程序时，它永远不会被调用。

此外，当我在OnStart函数中将auth状态侦听器添加到Firebase auth实例时，我的应用程序崩溃了。

我做错了什么？如何检查用户登录？

我正在使用Google登录Firebase。

我收到以下错误。

java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.demo.myblog / com.example.demo.myblog.LoginActivity}：java.lang.IllegalStateException：您需要使用Theme.AppCompat主题（这个活动的后代。

Answer 1

请在onCreate方法中初始化FirebaseUser的对象，如下所示 -

FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();

并在您的Activity的onStart方法中查看

if (user != null) {
         // Your user is authenticated 
        // Do your tasks;
        }

Answer 2

问题在于此错误行：

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.demo.myblog/com.example.demo.myblog.LoginActivity}: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.

您需要将Theme.AppCompat用于MainActivity

中的AndroidManifest.xml主题

您需要使用res/style.xml中的主题，如下所示：

<resources>

  <!-- Base application theme. -->
  <style name="AppTheme" parent="Theme.AppCompat">
    <!-- Customize your theme here. -->
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
    <item name="colorAccent">@color/colorAccent</item>
  </style>

</resources>

这样的事情：

<activity
    android:name=".MainActivity"
    android:label="@string/app_name"
    android:theme="@style/AppTheme"/>

应用程序在检查Firebase中的用户登录时不断崩溃

2 个答案: