从firebasedatabase检索值 [英] retrieving values from firebasedatabase
本文介绍了从firebasedatabase检索值的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我有一个Firebase实时数据库，我向它添加了值，然后我想检索这些值，但是它们没有显示在我的屏幕上.
I have a Firebase realtime database, and I add value to it, I then want to retrieve those values, but they don't show up on my screen.
这是可行的旧代码；
//ChatActivity class
mDatabaseforAllChatMessages.child(mAuth.getCurrentUser().getUid()).child(allChatId).setValue(allChatMessagesGet);
mDatabaseforAllChatMessages.child(userID).child(allChatId).setValue(allChatMessagesGet);
//AllChatMessages class
mDatabaseRef.child(mAuth.getCurrentUser().getUid()).addValueEventListener(new ValueEventListener(){
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot postSnapshot : dataSnapshot.getChildren()){
AllChatMessagesGet allChatMessagesGet = postSnapshot.getValue(AllChatMessagesGet.class);
}
allChatMessagesAdapter = new AllChatMessagesAdapter(AllChatMessages.this, allChatMessagesGetList);
recyclerView.setAdapter(allChatMessagesAdapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(AllChatMessages.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}});
我现在已将此代码更改为此:
I have now changed this code to this:
//ChatActivity class
mDatabaseforAllChatMessages.child(mAuth.getCurrentUser().getUid()).child(userID).child(uploadID).child(allChatId).setValue(allChatMessagesGet);
mDatabaseforAllChatMessages.child(userID).child(mAuth.getCurrentUser().getUid()).child(uploadID).child(allChatId).setValue(allChatMessagesGet);
和:
//AllChatMessages class
mDatabaseRef.child(mAuth.getCurrentUser().getUid()).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot postSnapshot : dataSnapshot.getChildren()){
AllChatMessagesGet allChatMessagesGet = postSnapshot.getValue(AllChatMessagesGet.class);
allChatMessagesGetList.add(allChatMessagesGet);
}
allChatMessagesAdapter = new AllChatMessagesAdapter(AllChatMessages.this, allChatMessagesGetList);
recyclerView.setAdapter(allChatMessagesAdapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(AllChatMessages.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});
那我为什么不能从新代码中找回我的价值?我该怎么解决?
So why am I not able to retrive my value from the new codes? How can I solve it?
public class AllChatMessagesAdapter extends RecyclerView.Adapter<AllChatMessagesAdapter.AllChatViewHolder> {
private Context mCtx;
private List<AllChatMessagesGet> ChatActivityList;
public AllChatMessagesAdapter(Context mctx, List<AllChatMessagesGet> chatActivityList){
this.mCtx = mctx;
this.ChatActivityList = chatActivityList;
}
@Override
public AllChatViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
LayoutInflater inflater = LayoutInflater.from(mCtx);
View viewList_allChatMessagesLayout = inflater.inflate(R.layout.allchatmessages_layout_list, parent, false);
return new AllChatViewHolder(viewList_allChatMessagesLayout);
}
@Override
public void onBindViewHolder(AllChatViewHolder holder, int position) {
AllChatMessagesGet allChatMessagesGet = ChatActivityList.get(position);
//from below class and Allchatmessagesget Class.
holder.textViewTitleOfUpload.setText(allChatMessagesGet.getUploadTitleString());
holder.textviewTitleOfMessage.setText(allChatMessagesGet.getMessageTextsent());
Glide.with(mCtx)
.load(allChatMessagesGet.getUploadImageURL())
.into(holder.imageView);
holder.imageView.setRotation(allChatMessagesGet.getUploadImageRotation());
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
//create new intent to start another activity
//add extras
//startactivity
}
});
}
@Override
public int getItemCount() {
return ChatActivityList.size();
}
public class AllChatViewHolder extends RecyclerView.ViewHolder {
public ImageView imageView;
public TextView textViewTitleOfUpload, textviewTitleOfMessage;
public AllChatViewHolder(View itemView) {
super(itemView);
//taken from allchatmessages_layout_list.xml
imageView = itemView.findViewById(R.id.imageofupload);
textViewTitleOfUpload = itemView.findViewById(R.id.textViewTitle);
textviewTitleOfMessage = itemView.findViewById(R.id.textViewmessage);
}
}
}
我现在还添加了Adapter类.
I have added the Adapter class aswell now.
这里是完整代码:请忽略我班上的注释，因为它们是不正确的注释，将被删除
here is full code: PLEASE IGNORE the COMMENTS on my classes since they are not correct comments and will be deleted
public class ChatActivity extends AppCompatActivity {
private String titleString, userID, uploadID, imageURL, userOnlineString, userEmail, uniqueID;
private Boolean userOnlineBoolean;
private int imageRotation;
private TextView titleCustomBar, lastSeenCustomBar;
private ImageView imageCustomBar;
private DatabaseReference mDatabaseRefUser, mDatabaseforAllChatMessages;
private FirebaseAuth mAuth;
private EditText addMessageEditText;
private FloatingActionButton sendMessageFab;
private ImageButton addImageToMessageImageButton;
private FirebaseListAdapter<ChatMessage> adapter;
private String allChatId;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat);
//activity_chat.xml
addImageToMessageImageButton = findViewById(R.id.add_image_id);
addMessageEditText = findViewById(R.id.add_message_input_id);
sendMessageFab = findViewById(R.id.send_message_fab_id);
mAuth = FirebaseAuth.getInstance();
mDatabaseRefUser = FirebaseDatabase.getInstance().getReference("Users");
mDatabaseforAllChatMessages = FirebaseDatabase.getInstance().getReference("AllChatMessages");
//Log.e("Lol", userOnlineString);
mDatabaseRefUser.child(mAuth.getCurrentUser().getUid()).child("Online").addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
userOnlineBoolean = dataSnapshot.getValue(Boolean.class);
//if(userOnlineBoolean==true){
// userOnlineString = "Online";
//setCustomOnlineOffline();
//}
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(ChatActivity.this, "some error", Toast.LENGTH_SHORT).show();
}
});
Intent intent = getIntent();
titleString = intent.getStringExtra("TITLE");
userID = intent.getStringExtra("USERID");
uploadID = intent.getStringExtra("UPLOADID");
imageRotation = intent.getIntExtra("IMAGEROTATION", 0);
imageURL = intent.getStringExtra("IMAGEURL");
userEmail = intent.getStringExtra("USEREMAIL");
ActionBar actionBar = getSupportActionBar();
actionBar.setDisplayShowCustomEnabled(true);
LayoutInflater layoutInflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE);
View customActionBar = layoutInflater.inflate(R.layout.chat_custombar, null);
actionBar.setCustomView(customActionBar);
titleCustomBar = findViewById(R.id.title_textview_id);
lastSeenCustomBar = findViewById(R.id.last_seen_textview_id);
imageCustomBar = findViewById(R.id.custom_image_id);
titleCustomBar.setText(titleString);
//getSupportActionBar().setDisplayHomeAsUpEnabled(true);
Glide.with(this).load(imageURL)
.into(imageCustomBar);
imageCustomBar.setRotation(imageRotation);
//lastSeenCustomBar.setText(userOnlineString);
/*mDatabaseRefUser.child(mAuth.getCurrentUser().getUid()).child("Chats").child(userID);
HashMap<String, String> userMap = new HashMap<>();
userMap.put("name", mAuth.getCurrentUser().getEmail());
userMap.put("Chat with;", userEmail);
userMap.put("image", uploadID);*/
//mDatabaseRefUser.setValue(userMap);
//uniqueID = mDatabaseRefUser.push().getKey();
displayChatMessage();
}
private void setCustomOnlineOffline() {
lastSeenCustomBar.setText(userOnlineString);
}
@Override
protected void onStart() {
super.onStart();
if(mAuth.getCurrentUser() == null){
Intent mainActivityIntent = new Intent(this, MainActivity.class);
startActivity(mainActivityIntent);
finish();
}
else {
mDatabaseRefUser.child(mAuth.getCurrentUser().getUid()).child("Online").setValue(true);
}
}
public void sendMessageToAnotherUser(View view) {
if(addMessageEditText.getText().toString().isEmpty()){
return;
}
else {
ChatBetweenUsers chatBetweenUsers = new ChatBetweenUsers(mAuth.getCurrentUser().getUid(), userID,
mAuth.getCurrentUser().getEmail(), userEmail, uploadID);
ChatBetweenUsers chatBetweenUsers2 = new ChatBetweenUsers(userID, mAuth.getCurrentUser().getUid(),
userEmail, mAuth.getCurrentUser().getEmail(), uploadID);
//user email is null! because old uploaded pics had no useremail in constructor. add new pics for change!
// add .child"messages" after .childuploadID ???
mDatabaseRefUser.child("Chat").child(mAuth.getCurrentUser().getUid())
.child(userID).child(uploadID).setValue(chatBetweenUsers);
mDatabaseRefUser.child("Chat").child(userID)
.child(mAuth.getCurrentUser().getUid()).child(uploadID).setValue(chatBetweenUsers2);
//FirebaseDatabase.getInstance().getReference().push().setValue(new ChatMessage(addMessageEditText.getText().toString(),
// FirebaseAuth.getInstance().getCurrentUser().getEmail()));
//This codes overwrites the previous value, maybe because of above code that setValue(chatbetweenUsers),
// must be without it
// mDatabaseRefUser.child("Chat").child(mAuth.getCurrentUser().getUid())
// .child(userID).child(uploadID).child("Messages").push().setValue(new ChatMessage(addMessageEditText.getText().toString(),
// mAuth.getCurrentUser().getEmail()));
//mDatabaseRefUser.child("Chat").child(userID)
// .child(mAuth.getCurrentUser().getUid()).child(uploadID).child("Messages").push().setValue(new ChatMessage(addMessageEditText.getText().toString(),
// userEmail));
mDatabaseRefUser.child("Chatting").child(mAuth.getCurrentUser().getUid())
.child(userID).child(uploadID).child("Messages").push().setValue(new ChatMessage(addMessageEditText.getText().toString(),
mAuth.getCurrentUser().getEmail()));
mDatabaseRefUser.child("Chatting").child(userID)
.child(mAuth.getCurrentUser().getUid()).child(uploadID).child("Messages").push().setValue(new ChatMessage(addMessageEditText.getText().toString(),
userEmail));
allChatId = mDatabaseforAllChatMessages.push().getKey();
AllChatMessagesGet allChatMessagesGet = new AllChatMessagesGet(imageURL, titleString, imageRotation, addMessageEditText.getText().toString(),
mAuth.getCurrentUser().getEmail(), userEmail);
mDatabaseforAllChatMessages.child(mAuth.getCurrentUser().getUid()).child(userID).child(uploadID).child(allChatId).setValue(allChatMessagesGet);
mDatabaseforAllChatMessages.child(userID).child(mAuth.getCurrentUser().getUid()).child(uploadID).child(allChatId).setValue(allChatMessagesGet);
//kod behövs ej tror jag.
addMessageEditText.setText("");
}
}
private void displayChatMessage() {
ListView listOfMessages = findViewById(R.id.list_of_messages);
//fix this code so message shows
adapter = new FirebaseListAdapter<ChatMessage>(this, ChatMessage.class, R.layout.list_item_message,
FirebaseDatabase.getInstance().getReference().child("Users").child("Chatting").child(mAuth.getCurrentUser().getUid()).child(userID)
.child(uploadID).child("Messages")) {
@Override
protected void populateView(View v, ChatMessage model, int position) {
TextView messageText, messageUser, messageTime;
messageText = v.findViewById(R.id.message_text);
messageUser = v.findViewById(R.id.message_user);
messageTime = v.findViewById(R.id.message_time);
model.setMessageTime(new Date().getTime());
messageText.setText(model.getMessageText());
messageUser.setText(model.getMessageUser());
messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)", model.getMessageTime()));
}
};
listOfMessages.setAdapter(adapter);
}
}
这是AllChatMessages的代码:
public class AllChatMessages extends AppCompatActivity {
private FirebaseAuth mAuth;
private RecyclerView recyclerView;
private AllChatMessagesAdapter allChatMessagesAdapter;
private List<AllChatMessagesGet> allChatMessagesGetList;
private DatabaseReference mDatabaseRef, mDatabaseRefUser;
private boolean online;
private FirebaseListAdapter<AllChatMessagesGet> adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_all_chat_messages);
mAuth = FirebaseAuth.getInstance();
allChatMessagesGetList = new ArrayList<>();
//from activity_all_chat_messages.xml
recyclerView = findViewById(R.id.allchatmessages_recycleview_id);
recyclerView.setHasFixedSize(true);
Log.e("lol", mAuth.getCurrentUser().getEmail());
recyclerView.setLayoutManager(new LinearLayoutManager(this));
mDatabaseRef = FirebaseDatabase.getInstance().getReference("AllChatMessages");
mDatabaseRefUser = FirebaseDatabase.getInstance().getReference("Users");
displayAllChatMessages();
}
private void displayAllChatMessages() {
//To get data out of uploads DataBase
mDatabaseRef.child(mAuth.getCurrentUser().getUid()).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
//Loop through all files in Uploads DataBase
for(DataSnapshot postSnapshot : dataSnapshot.getChildren()){
AllChatMessagesGet allChatMessagesGet = postSnapshot.getValue(AllChatMessagesGet.class);
//add if statement and then allChatMessagesGetList.clear when if statements are fulfilled
//such as same uploadid, same title, and same users from both side, then clear it? or just update the
//text somehow.
//allChatMessagesGetList.clear();
allChatMessagesGetList.add(allChatMessagesGet);
//filled the uploadImageList with the data from uploadImage from the Uploads DataBase
}
allChatMessagesAdapter = new AllChatMessagesAdapter(AllChatMessages.this, allChatMessagesGetList);
recyclerView.setAdapter(allChatMessagesAdapter);
}
@Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(AllChatMessages.this, databaseError.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}
}
推荐答案
要解决此问题，请在onStart()和onStop()方法中添加以下代码行.
To solve this, add the following lines of code in the onStart() and onStop() methods.
@Override
protected void onStart() {
super.onStart();
allChatMessagesAdapter.startListening();
}
@Override
protected void onStop() {
super.onStop();
if(allChatMessagesAdapter != null) {
allChatMessagesAdapter.stopListening();
}
}
为使其正常工作，您需要开始侦听更改.
In order to make it work, you need to start listening for changes.
这篇关于从firebasedatabase检索值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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