我使用了一个工作的RecyclerView作为另一个模板，但是在实现时犯了一些错误，但找不到。这是初始化视图的代码：
mMessageThreadList = new ArrayList<>();
mRecyclerView = findViewById(R.id.chat_list_recycler_view);
private void initRecyclerView() {
Log.d(TAG, "initRecyclerView Called");
//Initializes and sets up adapter
mAdapter = new ChatListRecyclerViewAdapter(mThreadList);
mRecyclerView.setAdapter(mAdapter);
Query query = mThreadCollection;
query.addSnapshotListener(new EventListener<QuerySnapshot>() {
@Override
public void onEvent(@Nullable QuerySnapshot queryDocumentSnapshots, @Nullable FirebaseFirestoreException e) {
for (DocumentChange documentChange : queryDocumentSnapshots.getDocumentChanges()) {
switch (documentChange.getType()) {
case ADDED:
Thread thread = documentChange.getDocument().toObject(Thread.class);
Log.d(TAG, "Last Message: " + thread.getLastMessage().getMessage());
mThreadList.add(thread);
mAdapter.notifyDataSetChanged();
}
}
}
});
}
请注意，SnapshotListener中的打印日志语句在打印时确实包含一个值，因此该信息是从Firebase返回的，只是不显示。这让我认为我的问题出在我的适配器/查看器上：
public class ChatListRecyclerViewAdapter extends RecyclerView.Adapter<ChatListRecyclerViewAdapter.ChatListViewHolder> {
private List<Thread> threadList;
ChatListRecyclerViewAdapter(List<Thread> threadList) {
this.threadList = threadList;
}
@NonNull
@Override
public ChatListViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_list_row, parent, false);
return new ChatListViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull ChatListViewHolder holder, int position) {
// This method fills fields with data for each list item
Log.d(TAG, "onBindViewholder called");
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("MMM hh:mm a");
final Thread thread = threadList.get(position);
char initial = thread.getPartnerName().charAt(0);
char uppercaseInitial = Character.toUpperCase(initial);
Log.d(TAG, thread.getLastMessage() + " " + thread.getPartnerID());
holder.partnerName.setText(thread.getPartnerName());
holder.authorInitial.setText(uppercaseInitial);
holder.lastMessageText.setText(thread.getLastMessage().getMessage());
holder.lastMessageTime.setText(simpleDateFormat.format(thread.getLastMessage().getTimestamp()));
}
@Override
public int getItemCount() {
return threadList.size();
}
//Viewholder stores the information about the layout and content of each list item, and serves as a template for each item of a RecyclerView
public class ChatListViewHolder extends RecyclerView.ViewHolder {
TextView partnerName;
TextView authorInitial;
TextView lastMessageText;
TextView lastMessageTime;
LinearLayout listTextHolder;
public ChatListViewHolder(View itemView) {
super(itemView);
partnerName = itemView.findViewById(R.id.partner_name);
authorInitial = itemView.findViewById(R.id.partner_initial);
lastMessageText = itemView.findViewById(R.id.last_message);
lastMessageTime = itemView.findViewById(R.id.last_message_time);
listTextHolder = itemView.findViewById(R.id.list_text_holder);
}
}
}
chat_list_row.xml文件：
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/single_thread_container"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical"
android:layout_marginTop="5dp"
android:layout_marginBottom="5dp"
android:background="@color/colorPrimaryDark">
<TextView
android:id="@+id/partner_initial"
android:background="@drawable/chat_list_circle"
android:layout_width="45dp"
android:layout_height="45dp"
android:layout_alignParentStart="true"
android:gravity="center"
android:text="A"
android:textSize="36sp"
tools:ignore="HardcodedText" />
<TextView
android:id="@+id/last_message_time"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentEnd="true"
android:padding="5dp"
android:fontFamily="@font/nunito_extralight"
android:text="@string/sample_time"
android:textColor="@android:color/darker_gray"
android:textSize="12sp"
android:typeface="normal" />
<LinearLayout
android:id="@+id/list_text_holder"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_toEndOf="@id/partner_initial"
android:layout_centerVertical="true"
android:orientation="vertical">
<TextView
android:id="@+id/partner_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="start"
android:layout_marginStart="5dp"
android:fontFamily="@font/nunito"
android:text="@string/sample_name"
android:textColor="@color/white"
android:textSize="14sp"
android:textStyle="bold"
android:typeface="sans" />
<TextView
android:id="@+id/last_message"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="5dp"
android:fontFamily="@font/nunito_extralight"
android:gravity="start"
android:text="@string/sample_message"
android:textColor="@android:color/darker_gray"
android:textSize="12sp"
android:typeface="normal" />
</LinearLayout>
</RelativeLayout>
编辑：RecyclerView所在的活动的布局。我还编辑了上面的代码以显示变量在视图中的附加位置：
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@color/colorPrimaryDark"
android:paddingLeft="0dp"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingRight="0dp"
android:paddingBottom="0dp"
tools:context="org.andrewedgar.theo.ChatListActivity">
<include
android:id="@+id/chat_list_toolbar"
layout="@layout/toolbar" />
<android.support.v7.widget.RecyclerView
android:id="@+id/chat_list_recycler_view"
android:layout_width="0dp"
android:layout_height="0dp"
android:layout_alignParentStart="true"
android:layout_centerVertical="true"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/chat_list_toolbar" />
<android.support.design.widget.FloatingActionButton
android:id="@+id/new_check_in_button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="end|bottom"
android:layout_marginEnd="16dp"
android:layout_marginBottom="16dp"
android:src="@drawable/ic_person_pin_circle_black_24dp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
</android.support.constraint.ConstraintLayout>
答案 0 :(得分：1)
好像您错过了添加RecyclerView的布局管理器一样。您能否添加它，然后重试
RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
recyclerView.setLayoutManager(mLayoutManager);
答案 1 :(得分：0)
您的recyclerview没有显示任何数据，因为适配器中的列表仍然为空。从Firebase提取数据后，您将添加到mThreadList，该线程仍然具有活动性而不是适配器。要更新适配器中的列表，您可以在适配器类中添加一个方法，并将列表传递给适配器，然后在其中传递notifyDataseChanged。
活动：
//after firebase task...
mAdapter.updateData(mThreadList);
适配器：添加新方法
void updateData(List<Thread> threadList){
this.threadList = threadList;
notifyDatasetChanged(); //notify adapter that new list is added
}