android - 无论我如何尝试，Firebase 用户 ID 均为空？

Question

我制作了一个应用程序，可以让用户登录并在谷歌地图上设置标记，并且该标记连接到属于设置它的用户的聊天室。

现在的问题是我无法在 Chatactivity 和 MapFragment 中获取 uid，无论我如何尝试，它一直显示 null，我不知道问题是什么 这是三个 Activity :

有人可以帮帮我吗~~

登录 Activity

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    auth = FirebaseAuth.getInstance();

    if (auth.getCurrentUser() != null) {
        startActivity(new Intent(LoginActivity.this, MainActivity.class));
        finish();
    }
    //authenticate user
    auth.signInWithEmailAndPassword(email, password)
            .addOnCompleteListener(LoginActivity.this, new OnCompleteListener<AuthResult>() {
                @Override
                public void onComplete(@NonNull Task<AuthResult> task) {
                    // If sign in fails, display a message to the user. If sign in succeeds
                    // the auth state listener will be notified and logic to handle the
                    // signed in user can be handled in the listener.
                    if (!task.isSuccessful()) {
                        // there was an error
                        if (password.length() < 6) {
                            edUserid.setError("密碼太短，請輸入超過6個字元!");
                        } else {
                            Toast.makeText(LoginActivity.this, "登入失敗", Toast.LENGTH_LONG).show();
                        }
                    } else {
                        Toast.makeText(getApplicationContext(),"登入成功",Toast.LENGTH_LONG).show();
                        startActivity(new Intent(LoginActivity.this, MainActivity.class));

                        finish();
                    }
                }
            });
}

聊天 Activity

    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            EditText input = (EditText)findViewById(R.id.input);

            // Read the input field and push a new instance
            // of ChatMessage to the Firebase database
            FirebaseDatabase.getInstance()
                    .getReference(CHAT_PATH)
                    .push()
                    .setValue(new ChatMessage(input.getText().toString(),
                            FirebaseAuth.getInstance()
                                    .getCurrentUser()
                                    .getDisplayName())
                    );

            // Clear the input
            input.setText("");
        }
    });
    ListView listOfMessages = (ListView)findViewById(R.id.list_of_messages);

    adapter = new FirebaseListAdapter<ChatMessage>(this, ChatMessage.class,
            R.layout.message, FirebaseDatabase.getInstance().getReference(CHAT_PATH)) {
        @Override
        protected void populateView(View v, ChatMessage model, int position) {
            // Get references to the views of message.xml
            TextView messageText = (TextView)v.findViewById(R.id.message_text);
            TextView messageUser = (TextView)v.findViewById(R.id.message_user);
            TextView messageTime = (TextView)v.findViewById(R.id.message_time);

            // Set their text
            messageText.setText(model.getMessageText());
            messageUser.setText(model.getMessageUser());

            // Format the date before showing it
            messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",
                    model.getMessageTime()));
        }
    };

    listOfMessages.setAdapter(adapter);

 }

}

MapFragment(其中一部分)

        mFirebaseDatabase = FirebaseDatabase.getInstance();


        mFirebaseRef = mFirebaseDatabase.getReference("Map/"+userUID);
        mFirebaseRef.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {

                LatLng myLatLon = dataSnapshot.getValue(FirebaseMarker.class).toLatLng();

                // stash the key in the title, for recall later

                Marker myMarker = mgoogleMap.addMarker(new MarkerOptions()
                        .position(myLatLon).draggable(true).icon(BitmapDescriptorFactory.fromResource(R.drawable.seedloc2)).title(dataSnapshot.getKey()));

                // cache the marker locally
                markers.put(dataSnapshot.getKey(), myMarker);
            }

            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {
                LatLng myLatLon = dataSnapshot.getValue(FirebaseMarker.class).toLatLng();

                // Move markers on the map if changed on Firebase
                Marker changedMarker = markers.get(dataSnapshot.getKey());
                changedMarker.setPosition(myLatLon);

            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {
                Marker deadMarker = markers.get(dataSnapshot.getKey());
                deadMarker.remove();
                markers.remove(dataSnapshot.getKey());
                Log.v(TAG, "moved !" + dataSnapshot.getValue());


            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                Log.v(TAG, "canceled!" + databaseError.getMessage());

            }
        });

    }
}

@Override
public void onMapReady(final GoogleMap googleMap) {
    MapsInitializer.initialize(getContext());

    mgoogleMap = googleMap;
    googleMap.setOnInfoWindowClickListener(new GoogleMap.OnInfoWindowClickListener(){

        @Override
        public void onInfoWindowClick(Marker marker) {
            Intent intent = new Intent(getActivity(),ChatActivity.class);
            startActivity(intent);



        }
    });

Answer 1

如果有一个 Activity 可以正确获取uid(正如您所说)，则将uid的值保存到变量中并将其存储到 Intent 并在 Activity 之间使用它。不需要在每个activity中都获取uid。您只需获取一次。

//FirstActivity
Intent intent = new Intent(FirstActivity.this, SecondActivity.class);
intent.putExtra("uid", uid);
startActivity(intent);

要在第二个 Activity 中取回 uid，请使用以下代码:

//SecondActivity
String uid = (String) getIntent().getExtras().get("uid");

如果您在整个应用程序中需要该 uid，请使用 SharedPreferences来存储它。

希望有帮助。