如何自动滚动到recyclerView的底部？
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【中文标题】如何自动滚动到recyclerView的底部？【英文标题】：How to scroll automatically to the bottom of the recyclerVew? 【发布时间】：2021-08-24 05:29:26 【问题描述】：我正在制作一个聊天应用程序，我需要滚动到回收站视图的底部以显示最后一条消息。 发这个问题的主要目的是问如何滚动到recyclerView的底部。 我已经在 readMessage() 方法中尝试了下面这行代码，但仍然无法正常工作。
groupChatRecyclerView.smoothScrollToPosition(messageAdapter.getItemCount());
对于recyclerView：groupChatRecyclerView.setHasFixedSize(true);
对于 LinearLayoutManager：
linearLayoutManager = new LinearLayoutManager(getApplicationContext()); linearLayoutManager.setStackFromEnd(true); linearLayoutManager.setReverseLayout(false); groupChatRecyclerView.setLayoutManager(linearLayoutManager);
请问有人可以帮我吗？ 代码：
private void readMessage()
mchat = new ArrayList<>();
reference = groupReference.child("Messages");
reference.addValueEventListener(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot)
mchat.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren())
GroupChats chat = snapshot.getValue(GroupChats.class);
mchat.add(chat);
messageAdapter = new GroupMessageAdapter(GroupMessageActivity.this, mchat, (LayoutInflater) getSystemService(LAYOUT_INFLATER_SERVICE));
groupChatRecyclerView.setAdapter(messageAdapter);
//linearLayoutManager.smoothScrollToPosition(groupChatRecyclerView, null, messageAdapter.getItemCount()-1);
// groupChatRecyclerView.smoothScrollToPosition(messageAdapter.getItemCount());
@Override
public void onCancelled(@NonNull DatabaseError error)
);
GroupMessageAdapter 代码：
package com.example.chats.Adapter;
public class GroupMessageAdapter extends
RecyclerView.Adapter<RecyclerView.ViewHolder>
private Context mContext;
public static final int MSG_TYPE_LEFT = 0;
public static final int MSG_TYPE_RIGHT = 1;
public static final int MSG_TYPE_IMAGE_LEFT = 2;
public static final int MSG_TYPE_IMAGE_RIGHT = 3;
private List<GroupChats> mChat;
FirebaseUser fuser;
LayoutInflater inflater;
DatabaseReference userRef = FirebaseDatabase.getInstance().getReference("Users");
public GroupMessageAdapter(Context mContext, List<GroupChats> mChat, LayoutInflater inflater)
this.mContext = mContext;
this.mChat = mChat;
this.inflater = inflater;
@NonNull
@Override
public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)
RecyclerView.ViewHolder viewHolder = null;
inflater = LayoutInflater.from(parent.getContext());
switch (viewType)
case MSG_TYPE_LEFT:
View textOnlyLViewHolder = inflater.inflate(R.layout.group_item_left, parent,false);
viewHolder = new LeftMessageG(textOnlyLViewHolder);
break;
case MSG_TYPE_RIGHT:
View textOnlyRViewHolder = inflater.inflate(R.layout.chat_item_right, parent,false);
viewHolder = new RightMessageG(textOnlyRViewHolder);
break;
case MSG_TYPE_IMAGE_LEFT:
View imageOnlyLViewHolder = inflater.inflate(R.layout.group_image_left, parent,false);
viewHolder = new LeftImageG(imageOnlyLViewHolder);
break;
case MSG_TYPE_IMAGE_RIGHT:
View imageOnlyRViewHolder = inflater.inflate(R.layout.image_right, parent,false);
viewHolder = new RightImageG(imageOnlyRViewHolder);
break;
default:
return viewHolder;
@Override
public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position)
GroupChats chat = mChat.get(position);
try
String mess = chat.getMessage();
userRef.child(chat.getSender()).addValueEventListener(new ValueEventListener()
@Override
public void onDataChange(@NonNull DataSnapshot snapsh)
if (snapsh.exists())
final String userImage = snapsh.child("imageURL").getValue().toString();
switch (holder.getItemViewType())
case MSG_TYPE_RIGHT:
RightMessageG rightM = (RightMessageG) holder;
rightM.show_messageR.setText(mess);
rightM.show_messageR.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
Toast.makeText(mContext, mess, Toast.LENGTH_SHORT).show();
);
rightM.text_seen.setVisibility(View.INVISIBLE);
break;
case MSG_TYPE_LEFT:
LeftMessageG leftM = (LeftMessageG) holder;
leftM.show_messageL.setText(mess);
Glide.with(mContext).load(userImage).into(leftM.photoGMember);
break;
case MSG_TYPE_IMAGE_RIGHT:
RightImageG rightI = (RightImageG) holder;
rightI.text_seen.setVisibility(View.INVISIBLE);
rightI.show_imageR.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
Intent intent = new Intent(mContext, FullImage.class);
intent.putExtra("image", mess);
mContext.startActivity(intent);
);
Glide.with(rightI.show_imageR).load(mess).into(rightI.show_imageR);
break;
case MSG_TYPE_IMAGE_LEFT:
LeftImageG leftI = (LeftImageG) holder;
Glide.with(mContext).load(userImage).into(leftI.photoGMember);
Glide.with(mContext).load(mess).into(leftI.show_imageL);
break;
@Override
public void onCancelled(@NonNull DatabaseError error)
);
catch (Exception e)
@Override
public int getItemCount()
return mChat.size();
@Override
public int getItemViewType(int position)
fuser = FirebaseAuth.getInstance().getCurrentUser();
if (mChat.get(position).getSender().equals(fuser.getUid()))
if (mChat.get(position).getType().equals("text"))
return MSG_TYPE_RIGHT;
else
return MSG_TYPE_IMAGE_RIGHT;
else
if (mChat.get(position).getType().equals("text"))
return MSG_TYPE_LEFT;
else
return MSG_TYPE_IMAGE_LEFT;
public class LeftMessageG extends RecyclerView.ViewHolder
public TextView show_messageL;
public CircleImageView text_seen,photoGMember;
public LeftMessageG(@NonNull View itemView)
super(itemView);
show_messageL = itemView.findViewById(R.id.show_messageLL);
text_seen = itemView.findViewById(R.id.text_seen);
photoGMember = itemView.findViewById(R.id.photoGMember);
public class RightMessageG extends RecyclerView.ViewHolder
public TextView show_messageR;
public CircleImageView text_seen;
public RightMessageG(@NonNull View itemView)
super(itemView);
show_messageR = itemView.findViewById(R.id.show_messageR);
text_seen = itemView.findViewById(R.id.text_seen);
public class RightImageG extends RecyclerView.ViewHolder
public ImageView show_imageR;
public CircleImageView text_seen;
public RightImageG(@NonNull View itemView)
super(itemView);
show_imageR = itemView.findViewById(R.id.show_imageR);
text_seen = itemView.findViewById(R.id.text_seen);
public class LeftImageG extends RecyclerView.ViewHolder
public ImageView show_imageL;
public CircleImageView text_seen, photoGMember;
public LeftImageG(@NonNull View itemView)
super(itemView);
show_imageL = itemView.findViewById(R.id.show_imageL);
text_seen = itemView.findViewById(R.id.text_seen);
photoGMember = itemView.findViewById(R.id.photoGMember);
【问题讨论】：
这能回答你的问题吗？ How to scroll to the bottom of a RecyclerView? scrollToPosition doesn't work 您的列表中显示了多少条消息？ 添加新消息后它会继续变化 【参考方案1】：试试这个
groupChatRecyclerView.smoothScrollToPosition(groupChatRecyclerView.getAdapter().getItemCount() - 1);
【讨论】：
【参考方案2】：在你的 readMessage 函数中添加这个
groupChatRecyclerView.scrollToPosition(mchat.size - 1);
滚动到添加到 RecyclerView 的最后一项。
【讨论】：
我已经尝试过了，但它不起作用。我不知道为什么 从你的代码看来你没有尝试过，你尝试了一些不同的东西（即注释掉）以上是关于如何自动滚动到recyclerView的底部？的主要内容，如果未能解决你的问题，请参考以下文章
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