回收器视图在活动重新启动后不更新

Question

所以，我不确定这个问题的标题，但它在这里。我的聊天室有一个回收器视图。第一次活动启动时，显示消息没有问题，但是在按后退按钮返回显示所有聊天室的主活动后，再次单击同一聊天室，它什么也不显示。然后，在发送消息后，它可以再次显示所有消息。我不确定发生了什么，请帮忙。哦，我已经尝试了一些东西并浏览了互联网，但因为我不确定关键字是什么，所以我现在很卡住

好的，事情是这样的

第一个主要活动，(忽略其他 2 个选项卡，它是空的(

主要活动

然后打开聊天室

首次打开聊天室罚款

然后按返回按钮，返回主活动，然后打开同一个房间，不显示聊天

聊天室不显示任何内容

然后在发送新消息后再次显示消息

新消息

我试图将通知数据集更改(( 放在各种事件上，如 onStart、onCreate 等，但没有任何效果;

这是我的聊天活动

package com.divistant.chat.ui.chat;
import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.ScrollView;
import android.widget.TextView;
import com.divistant.chat.R;
import com.divistant.signup.UserModel;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import com.google.firebase.database.ChildEventListener;
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 com.google.gson.Gson;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class ChatActivity extends AppCompatActivity {
LinearLayout layout;
ImageView send;
EditText message;
ScrollView scrollView;
DatabaseReference refrence1;
DatabaseReference refrence2;
RecyclerView rv;
List<ChatModel> chats = new ArrayList<>();
ChatActivityAdapter adapter;
FirebaseUser cUser;
UserModel target;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat);
Log.w("EVENT","ON Create");
Intent intent = getIntent();
target = (new Gson()).fromJson(intent.getStringExtra("target"),UserModel.class);
send = (ImageView)findViewById(R.id.sendButton);
message = (EditText)findViewById(R.id.messageArea);
scrollView = (ScrollView)findViewById(R.id.scrollView);
rv = (RecyclerView) findViewById(R.id.main_chat_rv);
cUser = FirebaseAuth.getInstance().getCurrentUser();
adapter = new ChatActivityAdapter(chats);
final LinearLayoutManager manager = new LinearLayoutManager(ChatActivity.this,
LinearLayoutManager.VERTICAL, false);
rv.setLayoutManager(manager);

refrence1 = FirebaseDatabase.getInstance()
.getReference()
.child("messages")
.child(cUser.getUid() + "_" + target.getUserId());
refrence2 = FirebaseDatabase.getInstance()
.getReference()
.child("messages")
.child(target.getUserId() + "_" + cUser.getUid());
send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Log.w("SEND","send message");
if(message.getText().toString().length() > 0){
ChatModel chat = new ChatModel();
chat.setSender(cUser.getEmail());
chat.setMessage(message.getText().toString());
chat.setReceiver(target.getEmailAddress());
chat.setSenderUid(cUser.getUid());
chat.setReceiverUid(target.getUserId());
chat.setTimestamp((new Date()).getTime());
DatabaseReference ref1 = refrence1.push();
ref1.setValue(chat);
DatabaseReference ref2 = refrence2.push();
ref2.setValue(chat);
message.setText("");
}
}
});

refrence1.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
chats.clear();
for(DataSnapshot snapshot :dataSnapshot.getChildren()){
ChatModel chat = new ChatModel();
chat.setSender(snapshot.child("sender").getValue(String.class));
chat.setMessage(snapshot.child("message").getValue(String.class));
chat.setReceiver(snapshot.child("receiver").getValue(String.class));
chat.setSenderUid(snapshot.child("senderUid").getValue(String.class));
chat.setReceiverUid(snapshot.child("receiverUid").getValue(String.class));
chat.setTimestamp(1592455659978L);
chats.add(chat);
}
adapter.setmChats(chats);
adapter.notifyDataSetChanged();
rv.scrollToPosition(adapter.getItemCount()-1);
Log.e("[CH]","DATACHANGE " + chats.size());
}

@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Log.e("[CH]","CANCEL");
}
});
refrence1.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
chats.clear();
adapter.notifyDataSetChanged();
rv.scrollToPosition(adapter.getItemCount()-1);
}
@Override
public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
Log.e("[CH]","DB CHANGE");
}
@Override
public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {
Log.e("[CH]","DB REMOVE");
}
@Override
public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
Log.e("[CH]","Child Moved");
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Log.e("[CH]","DB ERROR");
}
});

rv.setAdapter(adapter);
}
@Override
protected void onStart() {
super.onStart();
Log.e("[CH]","" + adapter.getItemCount());
}
}

然后，这是我的聊天活动适配器

package com.divistant.chat.ui.chat;
import android.text.TextUtils;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.divistant.chat.R;
import com.google.firebase.auth.FirebaseAuth;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
public class ChatActivityAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>{
private static final int VIEW_TYPE_ME = 1;
private static final int VIEW_TYPE_OTHER = 2;
List<ChatModel> mChats;

public void setmChats(List<ChatModel> mChats) {
this.mChats = mChats;
}
public ChatActivityAdapter(List<ChatModel> mChats) {
this.mChats = mChats;
Log.e("ADAPTER","CONSTRUCTED " + mChats.size());
}
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
RecyclerView.ViewHolder viewHolder = null;
switch (viewType) {
case VIEW_TYPE_ME:
View viewChatMine = layoutInflater.inflate(R.layout.chat_item, parent, false);
viewHolder = new MyChatViewHolder(viewChatMine);
break;
case VIEW_TYPE_OTHER:
View viewChatOther = layoutInflater.inflate(R.layout.chat_item_other, parent, false);
viewHolder = new OtherChatViewHolder(viewChatOther);
break;
}
return viewHolder;
}
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
if (TextUtils.equals(mChats.get(position).senderUid,
FirebaseAuth.getInstance().getCurrentUser().getUid())) {
configureMyChatViewHolder((MyChatViewHolder) holder, position);
} else {
configureOtherChatViewHolder((OtherChatViewHolder) holder, position);
}
}
private void configureMyChatViewHolder(final MyChatViewHolder myChatViewHolder, int position) {
ChatModel chat = mChats.get(position);
SimpleDateFormat sfd = new SimpleDateFormat("hh:mm a");
String date=sfd.format(new Date(chat.timestamp).getTime());
myChatViewHolder.senderMsgTime.setText(date);
myChatViewHolder.txtChatMessage.setText(chat.getMessage());
}
private void configureOtherChatViewHolder(final OtherChatViewHolder otherChatViewHolder, int position) {
final ChatModel chat = mChats.get(position);
SimpleDateFormat sfd = new SimpleDateFormat("hh:mm a");
String date=sfd.format(new Date(chat.timestamp).getTime());
otherChatViewHolder.receiverMsgTime.setText(date);
otherChatViewHolder.txtChatMessage.setText(chat.getMessage());
}
@Override
public int getItemCount() {
return mChats.size();
}
@Override
public int getItemViewType(int position) {
if (TextUtils.equals(mChats.get(position).senderUid,
FirebaseAuth.getInstance().getCurrentUser().getUid())) {
return VIEW_TYPE_ME;
} else {
return VIEW_TYPE_OTHER;
}
}
private static class MyChatViewHolder extends RecyclerView.ViewHolder {
private TextView txtChatMessage, txtUserAlphabet;
private TextView senderMsgTime;
public MyChatViewHolder(View itemView) {
super(itemView);
txtChatMessage = (TextView) itemView.findViewById(R.id.text_view_chat_message);
txtUserAlphabet = (TextView) itemView.findViewById(R.id.text_view_user_alphabet);
senderMsgTime=(TextView) itemView.findViewById(R.id.senderMsgTime);
}
}
private static class OtherChatViewHolder extends RecyclerView.ViewHolder {
private TextView txtChatMessage, txtUserAlphabet;
private TextView receiverMsgTime;
public OtherChatViewHolder(View itemView) {
super(itemView);
txtChatMessage = (TextView) itemView.findViewById(R.id.text_view_chat_message_ot);
txtUserAlphabet = (TextView) itemView.findViewById(R.id.text_view_user_alphabet_ot);
receiverMsgTime=(TextView) itemView.findViewById(R.id.receiverMsgTime_ot);
}
}


}

谢谢

Answer 1

这是因为您正在清除子事件侦听器上的列表，而不是在列表中添加新的子项，也没有将列表传递给适配器。

@Override
public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
chats.clear();
adapter.notifyDataSetChanged();
rv.scrollToPosition(adapter.getItemCount()-1);
}

现在通过添加行来更改代码

@Override
public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
chats.clear();
for(DataSnapshot snapshot :dataSnapshot.getChildren()){
ChatModel chat = new ChatModel();
chat.setSender(snapshot.child("sender").getValue(String.class));
chat.setMessage(snapshot.child("message").getValue(String.class));
chat.setReceiver(snapshot.child("receiver").getValue(String.class));
chat.setSenderUid(snapshot.child("senderUid").getValue(String.class));
chat.setReceiverUid(snapshot.child("receiverUid").getValue(String.class));
chat.setTimestamp(1592455659978L);
chats.add(chat);
}
adapter.setmChats(chats);
adapter.notifyDataSetChanged();
rv.scrollToPosition(adapter.getItemCount()-1);
}

Answer 2

在我的情况下，我使用了onResume()

@Override
protected void onResume() {
super.onResume();
adapter.notifyDataSetChanged();
}

Answer 3

你能把rv.setAdapter(adapter(放在rv.setLayoutManager(manager(之后吗？ 并且您验证方法是否总是调用DataChange(...(？

Answer 4

您可以在要刷新回收器视图的适配器中使用以下代码，例如在@Override public void onBackPressed(){}函数中。如果聊天数组已更改，则应刷新此适配器。

mAdapter = new ChatActivityAdapter(context, chats.get(chats.size() - 1), chats);
recyclerView.setAdapter(mAdapter);