添加新项目时，Android Firebase聊天RecyclerView自动滚动到底部 [英] Android Firebase chat RecyclerView auto scroll to bottom when new item is added

问题描述

我试图研究这个问题，但我找不到一个好的解决方案。

$开发一个使用firebase的android聊天。

b $ b

希望有人可以帮助我。

我的问题我希望RecyclerView自动滚动，如果添加新项目。


$ $ $
$覆盖
public View

这里是我的代码。 onCreateView（LayoutInflater inflater，ViewGroup容器，Bundle savedInstanceState）{
查看rootView = inflater.inflate（R.layout.chatlayoutchat，container，false）;

连接连通性= new Connectivity（）;
if（getActivity（））{
if（getArguments（）！= null）{
Firebase.setAndroidContext（this.getActivity（））;
String ccustomersid = getArguments（）。getString（customersid）;
String creferralae = getArguments（）。getString（referralae）;
String ccustomersname = getArguments（）。getString（customersname）;

customersid = ccustomersid;
referralae = creferralae;
customersname = ccustomersname;

Firebase.setAndroidContext（this.getActivity（））;


editText =（EditText）rootView.findViewById（R.id.editText）;

sendbutton =（Button）rootView.findViewById（R.id.button）;
mRecyclerView =（RecyclerView）rootView.findViewById（R.id.recycler_view）;
RecyclerView.LayoutManager layoutmgr = new LinearLayoutManager（getActivity（））;
mRecyclerView.setLayoutManager（layoutmgr）;
mRecyclerView.setItemAnimator（new DefaultItemAnimator（））;

final LinearLayoutManager linearLayoutManager = new LinearLayoutManager（getActivity（））;
//linearLayoutManager.setReverseLayout(true）;
linearLayoutManager.setStackFromEnd（true）;
mRecyclerView.setLayoutManager（linearLayoutManager）;

from_user = customersid;
to_user = referralae;
LoggedInUser = customersname;


//Log.v(\"NODE CREATED：，from_user ++ to_user）;


ref_chatchildnode1 = firebase_chatnode.child（from_user ++ to_user）;

// ref_chatchildnode2 = firebase_chatnode.child（to_user ++ from_user）;
sendbutton.setOnClickListener（new View.OnClickListener（）{
@Override
public void onClick（View view）{
newmsg = editText.getText（）。toString（）。trim （）;
ChatModel m = new ChatModel（）;
m.setSender（LoggedInUser）;
m.setMessage（newmsg）;
ref_chatchildnode1.push（）。setValue（m ）;
//ref_chatchildnode2.push().setValue(m）;
editText.setText（）;


}
}） ;
ref_chatchildnode1.addChildEventListener（new ChildEventListener（）{
@Override $ b $ public void onChildAdded（DataSnapshot dataSnapshot，String s）{
ChatModel chatmsg = dataSnapshot.getValue（ChatModel.class）;
chatmsgsList.add（chatmsg）;
}
$ b $ @覆盖
public void onChildChanged（DataSnapshot dataSnapshot，String s）{

}

@Override
public void onChildRemoved（DataSnapshot dataSnapshot）{


$ b @Override
public void onChildMoved（DataSnapshot dataSnapshot，String s）{

}
$ b $ @覆盖
public void onCancelled（FirebaseError firebaseError）{

}
}）;
$ b}

} else {
nointernet（）;
}

showGlobalContextActionBar（）;

return rootView;


@Override
public void onStart（）{
super.onStart（）;
mFirebaseAdapter1 = new FirebaseRecyclerAdapter< ChatModel，ChatMessageViewHolder>（ChatModel.class，
R.layout.textview，
ChatMessageViewHolder.class，
ref_chatchildnode1）{
@Override
protected void populateViewHolder（ChatMessageViewHolder chatMessageViewHolder，ChatModel m，int i）{


$ b $ chatMessageViewHolder.sender.setText（m.getSender（））;
chatMessageViewHolder.msg.setText（m.getMessage（））;

}
};
mRecyclerView.setAdapter（mFirebaseAdapter1）;

$ b $ / code>

解决方案

请参阅 Firebase for Android的第6步，它使用 AdapterDataObserver 为此：

  mFirebaseAdapter.registerAdapterDataObserver（new RecyclerView.AdapterDataObserver（）{
 @Override 
 public void onItemRangeInserted（int positionStart，int itemCount）{
 super.onItemRangeInserted（positionStart，itemCount）; 
 int friendlyMessageCount = mFirebaseAdapter.getItemCount（）; 
 int lastVisiblePosition = 
 mLinearLayoutManager.findLastCompletelyVisibleItemPosition（）; 
 //如果回收者视图最初被加载或者
 //用户在列表底部，滚动到底部
 //显示新添加的消息
 if（lastVisiblePosition == -1 || 
 （positionStart> =（friendlyMessageCount-1）&& 
 lastVisiblePosition ==（positionStart  -  1）））{
 mMessageRecyclerView.scrollToPosition（positionStart）; 
} 
} 
}）; 
  

im developing an android chat using firebase.

i tried to research about this problem but i cant find a good solutions.

hope someone can help me.

my problem i want the RecyclerView to auto scroll if new item is added.

here is my code.

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState){
    View rootView = inflater.inflate(R.layout.chatlayoutchat, container, false);

    Connectivity connectivity=new Connectivity();
    if(connectivity.isConnected(getActivity())) {
        if(getArguments() != null) {
            Firebase.setAndroidContext(this.getActivity());
            String ccustomersid = getArguments().getString("customersid");
            String creferralae = getArguments().getString("referralae");
            String ccustomersname = getArguments().getString("customersname");

            customersid = ccustomersid;
            referralae = creferralae;
            customersname = ccustomersname;

            Firebase.setAndroidContext(this.getActivity());


            editText = (EditText) rootView.findViewById(R.id.editText);

            sendbutton = (Button) rootView.findViewById(R.id.button);
            mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler_view);
            RecyclerView.LayoutManager layoutmgr = new LinearLayoutManager(getActivity());
            mRecyclerView.setLayoutManager(layoutmgr);
            mRecyclerView.setItemAnimator(new DefaultItemAnimator());

            final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());
            //linearLayoutManager.setReverseLayout(true);
            linearLayoutManager.setStackFromEnd(true);
            mRecyclerView.setLayoutManager(linearLayoutManager);

            from_user = customersid;
            to_user = referralae;
            LoggedInUser = customersname;


            //Log.v("NODE CREATED:", from_user + " " + to_user);


            ref_chatchildnode1 = firebase_chatnode.child(from_user + " " + to_user);

            //ref_chatchildnode2 = firebase_chatnode.child(to_user + " " + from_user);
            sendbutton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    newmsg = editText.getText().toString().trim();
                    ChatModel m = new ChatModel();
                    m.setSender(LoggedInUser);
                    m.setMessage(newmsg);
                    ref_chatchildnode1.push().setValue(m);
                    //ref_chatchildnode2.push().setValue(m);
                    editText.setText("");


                }
            });
            ref_chatchildnode1.addChildEventListener(new ChildEventListener() {
                @Override
                public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                    ChatModel chatmsg = dataSnapshot.getValue(ChatModel.class);
                    chatmsgsList.add(chatmsg);
                }

                @Override
                public void onChildChanged(DataSnapshot dataSnapshot, String s) {

                }

                @Override
                public void onChildRemoved(DataSnapshot dataSnapshot) {

                }

                @Override
                public void onChildMoved(DataSnapshot dataSnapshot, String s) {

                }

                @Override
                public void onCancelled(FirebaseError firebaseError) {

                }
            });

        }

    }else{
        nointernet();
    }

    showGlobalContextActionBar();

    return rootView;
}

@Override
public void onStart() {
    super.onStart();
    mFirebaseAdapter1 = new FirebaseRecyclerAdapter<ChatModel, ChatMessageViewHolder>(ChatModel.class,
            R.layout.textview,
            ChatMessageViewHolder.class,
            ref_chatchildnode1) {
        @Override
        protected void populateViewHolder(ChatMessageViewHolder chatMessageViewHolder, ChatModel m, int i) {



            chatMessageViewHolder.sender.setText(m.getSender());
            chatMessageViewHolder.msg.setText(m.getMessage());

        }
    };
    mRecyclerView.setAdapter(mFirebaseAdapter1);

}

解决方案

Have a look at step 6 of the Firebase codelab for Android, which uses an AdapterDataObserver for this:

mFirebaseAdapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
   @Override
   public void onItemRangeInserted(int positionStart, int itemCount) {
       super.onItemRangeInserted(positionStart, itemCount);
       int friendlyMessageCount = mFirebaseAdapter.getItemCount();
       int lastVisiblePosition =
              mLinearLayoutManager.findLastCompletelyVisibleItemPosition();
       // If the recycler view is initially being loaded or the 
       // user is at the bottom of the list, scroll to the bottom 
       // of the list to show the newly added message.
       if (lastVisiblePosition == -1 ||
               (positionStart >= (friendlyMessageCount - 1) &&
                       lastVisiblePosition == (positionStart - 1))) {
           mMessageRecyclerView.scrollToPosition(positionStart);
       }
   }
});

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