有我的活动：
public class EventDetailsActivity extends AppCompatActivity {
private Event event;
private ArrayList<User> subscribedUsers;
private RecyclerView mRecyclerView;
private String eventId;
private SubscribedUsersAdapter adapter;
private Context context;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_event_details);
context = this;
Bundle extras = getIntent().getExtras();
eventId = extras.getString("eventId");
setUpEvent();
}
private void setUpEvent() {
mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
final DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference().child("events").child(eventId);
mDatabase.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String eventType = dataSnapshot.child("eventType").getValue().toString();
String description = dataSnapshot.child("description").getValue().toString();
Object object = dataSnapshot.child("startingDate").getValue();
HashMap result = (HashMap) object;
int year = Integer.parseInt(result.get("year").toString());
int month = Integer.parseInt(result.get("month").toString());
int day = Integer.parseInt(result.get("date").toString());
int hour = Integer.parseInt(result.get("hours").toString());
int minute = Integer.parseInt(result.get("minutes").toString());
Date startingDate = new Date(year,month,day,hour,minute,0);
object = dataSnapshot.child("location").getValue();
result = (HashMap) object;
double latitude = Double.parseDouble(result.get("latitude").toString());
double longitude = Double.parseDouble(result.get("longitude").toString());
LatLng location = new LatLng(latitude,longitude);
String userId = dataSnapshot.child("userId").getValue().toString();
String userName = dataSnapshot.child("userName").getValue().toString();
String userPicture = dataSnapshot.child("userPicture").getValue().toString();
subscribedUsers = new ArrayList<User>();
if (dataSnapshot.hasChild("subscribedUsers")) {
mDatabase.child("subscribedUsers").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
String userId = childSnapshot.child("userId").getValue().toString();
String name = childSnapshot.child("name").getValue().toString();
String picture = childSnapshot.child("picture").getValue().toString();
User subscribedUser = new User(userId, name, picture);
if (containsUser(subscribedUsers, subscribedUser) == -1) {
subscribedUsers.add(subscribedUser);
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
event = new Event(eventId, eventType,description,startingDate,location,userId, userName, userPicture);
setText();
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
private void setText()
{
ImageView mProfilePicture = (ImageView) findViewById(R.id.profilePicture);
if (!EventDetailsActivity.this.isFinishing()) {
Glide
.with(this)
.load(event.getUserPicture())
.into(mProfilePicture);
}
TextView mUserName = (TextView) findViewById(R.id.userName);
mUserName.setText(event.getUserName());
TextView mEventType = (TextView) findViewById(R.id.eventType);
mEventType.setText(event.getEventType());
TextView mDescription = (TextView) findViewById(R.id.description);
mDescription.setText(event.getDescription());
if (!EventDetailsActivity.this.isFinishing()) {
SupportMapFragment mapFragment = (SupportMapFragment) getSupportFragmentManager()
.findFragmentById(R.id.mapView);
mapFragment.getMapAsync(new OnMapReadyCallback()
{
@Override
public void onMapReady(GoogleMap googleMap) {
googleMap.clear();
googleMap.addMarker(new MarkerOptions().position(event.getLocation()));
googleMap.animateCamera(CameraUpdateFactory.newLatLngZoom(event.getLocation(),12.0f));
}
});
}
TextView mStartingDate = (TextView) findViewById(R.id.startingDate);
Date startingDate = event.getStartingDate();
String displayText = String.valueOf(startingDate.getYear());
int month = startingDate.getMonth() + 1;
if (month/10 == 0)
{
displayText = displayText + ".0" + month;
}
else
{
displayText = displayText + "." + month;
}
if (startingDate.getDate()/10 == 0)
{
displayText = displayText + ".0" + startingDate.getDate();
}
else
{
displayText = displayText + "." + startingDate.getDate();
}
if (startingDate.getHours()/10 == 0)
{
displayText = displayText + ". 0" + startingDate.getHours();
}
else
{
displayText = displayText + ". " + startingDate.getHours();
}
if (startingDate.getMinutes()/10 == 0)
{
displayText = displayText + ":0" + startingDate.getMinutes();
}
else
{
displayText = displayText + ":" + startingDate.getMinutes();
}
mStartingDate.setText(displayText);
setUpRecyclerView();
subscribe();
}
private void setUpRecyclerView() {
adapter = new SubscribedUsersAdapter(this,subscribedUsers);
mRecyclerView.setAdapter(adapter);
}
private void subscribe()
{
FirebaseAuth mAuth = FirebaseAuth.getInstance();
if (mAuth.getCurrentUser() != null) {
final String userId = mAuth.getCurrentUser().getUid();
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference().child("users").child(userId);
mDatabase.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String userName = dataSnapshot.child("name").getValue().toString();
String userPicture = dataSnapshot.child("picture").getValue().toString();
User user = new User(userId, userName, userPicture);
userSubscribe(user);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
else
{
userSubscribe(null);
}
}
private void userSubscribe(final User user) {
Button mSubscribeButton = (Button) findViewById(R.id.subscribeButton);
if (user == null)
{
mSubscribeButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(EventDetailsActivity.this, getResources().getString(R.string.logInToSubscribe), Toast.LENGTH_LONG).show();
Intent loginIntent = new Intent(EventDetailsActivity.this, LoginActivity.class);
loginIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(loginIntent);
}
});
}
else if (containsUser(subscribedUsers,user) == -1)
{
mSubscribeButton.setText(getResources().getString(R.string.subscribe));
mSubscribeButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference().child("events").child(event.getEventId());
subscribedUsers.add(user);
mDatabase.child("subscribedUsers").setValue(subscribedUsers);
}
});
}
else
{
mSubscribeButton.setText(getResources().getString(R.string.unsubscribe));
mSubscribeButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
DatabaseReference mDatabase = FirebaseDatabase.getInstance().getReference().child("events").child(event.getEventId());
int position = containsUser(subscribedUsers,user);
subscribedUsers.remove(position);
mDatabase.child("subscribedUsers").removeValue();
mDatabase.child("subscribedUsers").setValue(subscribedUsers);
}
});
}
}
@Override
public void onBackPressed() {
super.onBackPressed();
this.finish();
}
private int containsUser(ArrayList<User> users, User user)
{
for (int i=0; i<users.size(); ++i)
{
if (users.get(i).getUserId().equals(user.getUserId()))
{
return i;
}
}
return -1;
}
}
我的适配器：
public class SubscribedUsersAdapter extends RecyclerView.Adapter<SubscribedUsersAdapter.ViewHolder>{
private Context context;
private ArrayList<User> items;
public SubscribedUsersAdapter(Context context, ArrayList<User> items) {
this.context = context;
this.items = items;
}
protected static class ViewHolder extends RecyclerView.ViewHolder {
public ImageView mProfilePictureView;
public TextView mUserName;
public ViewHolder(View itemView) {
super(itemView);
mProfilePictureView = (ImageView) itemView.findViewById(R.id.profilePictureView);
mUserName = (TextView) itemView.findViewById(R.id.userName);
}
}
@Override
public SubscribedUsersAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.single_user, parent, false);
return new ViewHolder(v);
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
final User item = items.get(position);
Glide
.with(context)
.load(item.getPicture())
.into(holder.mProfilePictureView);
holder.mUserName.setText(item.getName());
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent profileIntent = new Intent(context, ProfileActivity.class);
profileIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
profileIntent.putExtra("userId", item.getUserId());
context.startActivity(profileIntent);
}
});
}
@Override
public int getItemCount() {
return items.size();
}
}
当活动首先开始时，数据会在RecyclerView中很好地显示，但如果用户订阅了该事件或取消订阅，则RecyclerView将为空。 我尝试使用notifyDataSetChanged，notifyItemRangeInserted，notifyItemRangeRemoved，但没有一个工作或我没有使用它。我不知道。 谢谢你的帮助！
答案 0 :(得分：0)
for (DataSnapshot childSnapshot : dataSnapshot.getChildren()) {
String userId = childSnapshot.child("userId").getValue().toString();
String name = childSnapshot.child("name").getValue().toString();
String picture = childSnapshot.child("picture").getValue().toString();
User subscribedUser = new User(userId, name, picture);
if (containsUser(subscribedUsers, subscribedUser) == -1) {
subscribedUsers.add(subscribedUser);
}
}
之后只需添加此行
adapter.notifyDataSetChanged();