我的布局上看不到任何FirebaseRecyclerAdapter项目

我试图从Firebase数据库检索数据到我的布局，我无法在布局中看到任何FirebaseRecyclerAdapter项目，请帮忙。 我按照教程说明了如何做到这一点，当我运行应用程序时，我没有看到任何项目，但我可以滚动。

 public class Home extends AppCompatActivity { Button logout; FirebaseAuth firebaseAuth; private static final String Tag = "Home"; DatabaseReference dbUsers; DatabaseReference db; private RecyclerView mBlogList; FirebaseAuth.AuthStateListener authStateListener; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_home); logout = (Button) findViewById(R.id.logout); dbUsers = FirebaseDatabase.getInstance().getReference().child("Users"); Log.d(Tag, "onCreate: starting"); firebaseAuth = FirebaseAuth.getInstance(); dbUsers.keepSynced(true); db = FirebaseDatabase.getInstance().getReference().child("Blog"); db.keepSynced(true); mBlogList = (RecyclerView)findViewById(R.id.Blog_List); mBlogList.setHasFixedSize(true); mBlogList.setLayoutManager(new LinearLayoutManager(this)); setUpNav(); authStateListener = new FirebaseAuth.AuthStateListener() { @Override public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) { if (firebaseAuth.getCurrentUser() == null) { Intent lgnIntent = new Intent(getApplicationContext(), MainActivity.class); lgnIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(lgnIntent); } } }; } @Override protected void onStart() { super.onStart(); firebaseAuth.addAuthStateListener(authStateListener); checkUser(); FirebaseRecyclerOptions options = new FirebaseRecyclerOptions.Builder() .setQuery(db, Postzone.class) .build(); FirebaseRecyclerAdapter firebaseRecyclerAdapter = new FirebaseRecyclerAdapter(options) { @Override protected void onBindViewHolder(@NonNull PostViewHolder holder, int position, @NonNull Postzone model) { final String post_key = getRef(position).getKey().toString(); holder.setTitle(model.getTitle()); holder.setDesc(model.getDesc()); holder.setName(model.getUsername()); holder.setImage(getApplicationContext(),model.getImageUrl()); holder.mView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { Intent singleActivity = new Intent(Home.this, SinglePostActivity.class); singleActivity.putExtra("PostID", post_key); startActivity(singleActivity); } }); } @Override public PostViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.blog_row, parent, false); return new PostViewHolder(view); } }; mBlogList.setAdapter(firebaseRecyclerAdapter); } public static class PostViewHolder extends RecyclerView.ViewHolder{ View mView; public PostViewHolder(View itemView) { super(itemView); mView= itemView; } public void setTitle(String title){ TextView post_title = (TextView) mView.findViewById(R.id.post_title); post_title.setText(title); } public void setName(String name){ TextView post_user = (TextView) mView.findViewById(R.id.madeBy); post_user.setText(name); } public void setDesc(String desc){ TextView post_desc = (TextView) mView.findViewById(R.id.post_desc); post_desc.setText(desc); } public void setImage(Context ctx, String image){ ImageView img = (ImageView) mView.findViewById(R.id.post_image); Picasso.with(ctx).load(image).into(img); } } private void checkUser() { if (firebaseAuth.getCurrentUser() != null) { final String user_id = firebaseAuth.getCurrentUser().getUid(); dbUsers.addValueEventListener(new ValueEventListener() { @Override public void onDataChange(DataSnapshot dataSnapshot) { if (!dataSnapshot.hasChild(user_id)) { Intent main = new Intent(Home.this, Account_Setup.class); main.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(main); } } @Override public void onCancelled(DatabaseError databaseError) { } }); } } private void setUpNav() { Log.d(Tag, "setUpNav: starting func."); BottomNavigationViewEx nav = (BottomNavigationViewEx) findViewById(R.id.bottomNavViewBar); BottomNavigationViewHelper.setupBottomNav(nav); BottomNavigationViewHelper.enableNav(Home.this, nav); Menu menu = nav.getMenu(); MenuItem item = menu.getItem(0); item.setChecked(true); } } 

这是Home.xml布局：

这是博客类：

 public class Postzone { private String title, desc, imageUrl, username, profImg; public Postzone(String title, String desc, String imageUrl, String username, String profImg) { this.title = title; this.desc = desc; this.profImg = profImg; this.imageUrl=imageUrl; this.username = username; } public Postzone() { } public void setImageUrl(String imageUrl) { this.imageUrl = imageUrl; } public void setUsername(String username) { this.username = username; } public void setTitle(String title) { this.title = title; } public void setDesc(String desc) { this.desc = desc; } public String getImageUrl() { return imageUrl; } public String getTitle() { return title; } public String getDesc() { return desc; } public String getUsername() { return username; } public String getProfImg() { return profImg; } public void setProfImg(String profImg) { this.profImg = profImg; } } 

这是博客行：

Answer 1

您所关注的教程是错误的。 要解决您的问题，请考虑执行以下步骤。

1. 移动onCreate()方法中的onStart()方法中的所有代码，除了以下两行代码：

    super.onStart(); firebaseAuth.addAuthStateListener(authStateListener); 

2. 使您的firebaseRecyclerAdapter可变全局：

    private FirebaseRecyclerAdapter firebaseRecyclerAdapter; 

3. 从onCreate()方法中删除FirebaseRecyclerAdapter 。

4. 在onStart()和onStop()方法中添加以下代码行。

    @Override protected void onStart() { super.onStart(); firebaseRecyclerAdapter.startListening(); } @Override protected void onStop() { super.onStop(); if(firebaseRecyclerAdapter != null) { firebaseRecyclerAdapter.stopListening(); } } 

5. 最重要的是从类声明中删除static关键字。 应该只是：

    public class PostViewHolder extends RecyclerView.ViewHolder {}