所以,我正在使用Firebase UI从数据库中获取数据。它看起来像这样:
我想迭代“消息”来获取每个孩子,并在我的应用程序中将其显示为消息。这就是我的UserMessage类看起来很相似的方式:
public class UserMessage {
private String mUserLogin;
private String mUserMessage;
private String mUID;
UserMessage(String userLogin, String userMessage, String uid) {
mUserLogin = userLogin;
mUserMessage = userMessage;
mUID = uid;
}
public String getmUserLogin() {
return mUserLogin;
}
public void setmUserLogin(String mUserLogin) {
this.mUserLogin = mUserLogin;
}
public String getmUserMessage() {
return mUserMessage;
}
public String getmUID() {
return mUID;
}
public void setmUID(String mUID) {
this.mUID = mUID;
}
public void setmUserMessage(String mUserMessage) {
this.mUserMessage = mUserMessage;
}
}
我想通过FirebaseRecyclerOptions获取它:
FirebaseRecyclerOptions<UserMessage> options =
new FirebaseRecyclerOptions.Builder<UserMessage>()
.setQuery(firebaseDatabaseModel.getQuery(), new SnapshotParser<UserMessage>() {
@NonNull
@Override
public UserMessage parseSnapshot(@NonNull DataSnapshot snapshot) {
Log.d("snapshot length", String.valueOf(snapshot.getChildrenCount()));
return snapshot.getValue(UserMessage.class);
}
})
.build();
这是我的firebaseDatabaseModel.getQuery()方法的样子:
public Query getQuery() {
DatabaseReference messageReference = database.child("messages");
return messageReference.limitToLast(50);
}
这就是我想在FirebaseRecyclerAdapter中设置数据的方式
class ChatMessagesAdapter extends FirebaseRecyclerAdapter<UserMessage, ChatMessagesAdapter.ChatHolder> {
private UserMessage[] userMessages;
/**
* Initialize a {@link RecyclerView.Adapter} that listens to a Firebase query. See
* {@link FirebaseRecyclerOptions} for configuration options.
*
* @param options
*/
public ChatMessagesAdapter(@NonNull FirebaseRecyclerOptions<UserMessage> options) {
super(options);
userMessages = (UserMessage[]) options.getSnapshots().toArray();
}
@Override
protected void onBindViewHolder(@NonNull ChatHolder holder, int position, @NonNull UserMessage model) {
holder.message.setText(userMessages[position].getmUserMessage());
holder.user.setText(userMessages[position].getmUserLogin());
}
@NonNull
@Override
public ChatHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_message, parent, false);
return new ChatHolder(view);
}
static class ChatHolder extends RecyclerView.ViewHolder {
@BindView(R.id.user_message)
TextView message;
@BindView(R.id.user_login)
TextView user;
private ChatHolder(View itemView) {
super(itemView);
ButterKnife.bind(itemView);
}
}
}
问题是,无论我如何通过数组向FirebaseRecyclerAdapter发送选项(用户消息),它总是有0个计数。可能问题在于自定义解析器(我必须正确编写它),但我的调试器只是跳过这部分代码:
public UserMessage parseSnapshot(@NonNull DataSnapshot snapshot) {
Log.d("snapshot length", String.valueOf(snapshot.getChildrenCount()));
return snapshot.getValue(UserMessage.class);
}
所以我甚至无法检查我在这里做错了什么。我已经尝试了几个小时了,我真的不知道如何处理它。
//编辑1:由于@Alex Malmo建议,我已将数据库密钥更改为:
和UserMessage.class:
public class UserMessage {
private String userLogin, userMessage, uid;
public UserMessage() {}
public UserMessage(String userLogin, String userMessage, String uid) {
this.userLogin = userLogin;
this.userMessage = userMessage;
this.uid = uid;
}
public String getUserLogin() { return userLogin; }
public String getUserMessage() { return userMessage; }
public String getUid() { return uid; }
}
看起来事情仍然在FirebaseRecyclerOptions中创建。我试过这两种方法:
FirebaseRecyclerOptions<UserMessage> options = new FirebaseRecyclerOptions.Builder<UserMessage>()
.setQuery(query,
UserMessage.class)
.build();
和
FirebaseRecyclerOptions<UserMessage> options = new FirebaseRecyclerOptions.Builder<UserMessage>()
.setQuery(query,
new SnapshotParser<UserMessage>() {
@NonNull
@Override
public UserMessage parseSnapshot(@NonNull DataSnapshot snapshot) {
return snapshot.getValue(UserMessage.class);
}
})
.build();
在这两种情况下 - setQuery方法(解析部分)中的第二个参数似乎被忽略(compilator只是跳过那部分 - 它得到正确的查询,并直接转到.build()),这似乎是一个完整的问题,空数据在适配器。
您的代码中的问题是您使用错误的getter来填充您的字段。在以小写字母开头的模型类字段中。当您使用名为mUserLogin
的字段时,Firebase正在寻找名为getMUserLogin()
而不是getmUserLogin()
的getter。看大写字母M
与小写m
字母?这可能是你什么也得不到的最可能的原因。模型类的正确方式应该是这样的:
public class UserMessage {
private String userLogin, userMessage, uid;
public UserMessage() {}
public UserMessage(String userLogin, String userMessage, String uid) {
this.userLogin = userLogin;
this.userMessage = userMessage;
this.uid = uid;
}
public String getUserLogin() { return userLogin; }
public String getUserMessage() { return userMessage; }
public String getUid() { return uid; }
}
要在数据库中获得正确的数据,只需删除旧数据并添加新数据即可。您的代码现在应该可以使用
你也可以看看Java Naming Conventions。
好的,我终于解决了。问题是,我完全误解了FirebaseRecyclerOptions函数。我完全确定它在其中传递数据,整个事情是我试图获取数据,而不让整个方法完成它的工作。
所以我改变了适配器结构:
class ChatMessagesAdapter extends FirebaseRecyclerAdapter<UserMessage, ChatMessagesAdapter.ChatHolder> {
private UserMessage[] userMessages;
/**
* Initialize a {@link RecyclerView.Adapter} that listens to a Firebase query. See
* {@link FirebaseRecyclerOptions} for configuration options.
*
* @param options
*/
public ChatMessagesAdapter(@NonNull FirebaseRecyclerOptions<UserMessage> options) {
super(options);
userMessages = (UserMessage[]) options.getSnapshots().toArray();
}
@Override
protected void onBindViewHolder(@NonNull ChatHolder holder, int position, @NonNull UserMessage model) {
holder.message.setText(userMessages[position].getmUserMessage());
holder.user.setText(userMessages[position].getmUserLogin());
}
@NonNull
@Override
public ChatHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_message, parent, false);
return new ChatHolder(view);
}
static class ChatHolder extends RecyclerView.ViewHolder {
@BindView(R.id.user_message)
TextView message;
@BindView(R.id.user_login)
TextView user;
private ChatHolder(View itemView) {
super(itemView);
ButterKnife.bind(itemView);
}
}
至:
class ChatMessagesAdapter extends FirebaseRecyclerAdapter<UserMessage, ChatMessagesAdapter.ChatHolder> {
private ArrayList<UserMessage> messagesList = new ArrayList<>();
/**
* Initialize a {@link RecyclerView.Adapter} that listens to a Firebase query. See
* {@link FirebaseRecyclerOptions} for configuration options.
*
* @param options
*/
ChatMessagesAdapter(@NonNull FirebaseRecyclerOptions<UserMessage> options) {
super(options); }
@Override
protected void onBindViewHolder(@NonNull ChatHolder holder, int position, @NonNull UserMessage model) {
messagesList.add(model);
holder.message.setText(messagesList.get(position).getUserMessage());
holder.user.setText(messagesList.get(position).getUserLogin());
}
@NonNull
@Override
public ChatHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_message, parent, false);
return new ChatHolder(this,view);
}
static class ChatHolder extends RecyclerView.ViewHolder {
@BindView(R.id.user_message)
TextView message;
@BindView(R.id.user_login)
TextView user;
private ChatHolder(ChatMessagesAdapter chatMessagesAdapter, View itemView) {
super(itemView);
ButterKnife.bind(this, itemView);
}
}
}
所以,如果你对整个FirebaseUI有任何问题,我认为上面是正确的例子。
感谢@Alex Malmo和@Yupi的建议!