我正在构建一个简单的聊天应用程序。在用户片段中，如果我们单击用户，则会崩溃，如果有以前的聊天，请转到上一个活动。虽然没有与该用户片段进行聊天的情况很好，但是当我们在Firebase上键入消息并单击“发送消息存储”并且应用程序崩溃时，类似地，如果存在聊天，聊天片段也会崩溃。
我认为问题出在mReference.addValueEventListener(new ValueEventListener())方法中。代码和错误在下面给出。我看到了其他答案，但对我的代码不理解。
MessageActivity.java
public class MessageActivity extends AppCompatActivity {
CircleImageView profile_image;
TextView username;
FirebaseUser mFirebaseUser;
DatabaseReference mDatabaseReference;
ImageView btn_send;
EditText send_msg;
Intent mIntent;
MessageAdapter mMessageAdapter;
List<Chat> mChats;
RecyclerView mRecyclerView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_message);
Toolbar toolbar = findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
getSupportActionBar().setTitle("");
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
toolbar.setNavigationOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
finish();
}
});
profile_image = findViewById(R.id.profile_image);
username = findViewById(R.id.username);
btn_send = findViewById(R.id.img_btn_send);
send_msg = findViewById(R.id.text_send);
mRecyclerView = findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getApplicationContext());
linearLayoutManager.setStackFromEnd(true);
mRecyclerView.setLayoutManager(linearLayoutManager);
mIntent = getIntent();
final String userid = mIntent.getStringExtra("userid");
mFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
mDatabaseReference = FirebaseDatabase.getInstance().getReference("Users").child(userid);
btn_send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String msg = send_msg.getText().toString();
if (!msg.equals("")){
sendMessage(mFirebaseUser.getUid(), userid, msg);
}
send_msg.setText("");
}
});
mDatabaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
User user = dataSnapshot.getValue(User.class);
assert user != null;
username.setText(user.getUsername());
if ( user.getImageURL().equals("default")){
profile_image.setImageResource(R.mipmap.ic_launcher_round);
}else {
Glide.with(MessageActivity.this).load(user.getImageURL()).into(profile_image);
}
readMessage(mFirebaseUser.getUid(), userid, user.getImageURL());
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
private void sendMessage(String sender, String receiver, String message){
DatabaseReference mDatabaseReference = FirebaseDatabase.getInstance().getReference();
HashMap<String, Object> hashMap = new HashMap<>();
hashMap.put("sender", sender);
hashMap.put("receiver", receiver);
hashMap.put("message", message);
mDatabaseReference.child("Chats").setValue(hashMap);
}
private void readMessage(final String myId, final String userID, final String imageURL){
mChats = new ArrayList<>();
mDatabaseReference = FirebaseDatabase.getInstance().getReference("Chats");
mDatabaseReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
mChats.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
Chat chat = dataSnapshot1.getValue(Chat.class);
assert chat != null;
if (chat.getReceiver().equals(myId) && chat.getSender().equals(userID) || chat.getReceiver().equals(userID) && chat.getSender().equals(myId)){
mChats.add(chat);
}
mMessageAdapter = new MessageAdapter(MessageActivity.this, mChats, imageURL);
mRecyclerView.setAdapter(mMessageAdapter);
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
}
ChatsFragment.java
public class ChatsFragment extends Fragment {
private RecyclerView mRecyclerView;
private UserAdapter mUserAdapter;
private List<User> mUsers;
FirebaseUser fUser;
DatabaseReference mReference;
private List<String> userList;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_chats, container, false);
mRecyclerView = view.findViewById(R.id.recycler_view);
mRecyclerView.setHasFixedSize(true);
mRecyclerView.setLayoutManager(new LinearLayoutManager(getContext()));
fUser = FirebaseAuth.getInstance().getCurrentUser();
userList = new ArrayList<>();
mReference = FirebaseDatabase.getInstance().getReference("Chats");
mReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
userList.clear();
for (DataSnapshot snapshot: dataSnapshot.getChildren()){
Chat chat = snapshot.getValue(Chat.class);
if (chat.getSender().equals(fUser.getUid())){
userList.add(chat.getReceiver());
}
if (chat.getReceiver().equals(fUser.getUid())){
userList.add(chat.getSender());
}
}
readChats();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
return view;
}
private void readChats() {
mUsers = new ArrayList<>();
mReference = FirebaseDatabase.getInstance().getReference("Users");
mReference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
mUsers.clear();
for (DataSnapshot snapshot: dataSnapshot.getChildren()){
User user = snapshot.getValue(User.class);
for (String id : userList){
if (user.getId().equals(id)){
if (mUsers.size() != 0){
for ( User user1 : mUsers){
if ( !user.getId().equals(user1.getId()));
mUsers.add(user);
}
}
else{
mUsers.add(user);
}
}
}
}
mUserAdapter = new UserAdapter(getContext(), mUsers);
mRecyclerView.setAdapter(mUserAdapter);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
}
错误是：
com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(com.google.firebase:firebase-database@@16.0.4:423)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(com.google.firebase:firebase-database@@16.0.4:214)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(com.google.firebase:firebase-database@@16.0.4:79)
at com.google.firebase.database.DataSnapshot.getValue(com.google.firebase:firebase-database@@16.0.4:212)
at com.google.firebase.database.core.ValueEventRegistration.fireEvent(com.google.firebase:firebase-database@@16.0.4:75)
at com.google.firebase.database.core.view.DataEvent.fire(com.google.firebase:firebase-database@@16.0.4:63)
at com.google.firebase.database.core.view.EventRaiser$1.run(com.google.firebase:firebase-database@@16.0.4:55)
at android.os.Handler.handleCallback(Handler.java:754)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:163)
at android.app.ActivityThread.main(ActivityThread.java:6228)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:904)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)