Java RecyclerView未在活动开始时调用CreateViewHolder

我一直在尝试实现一个简单的可滚动列表，该列表使用名为MyOrganisedEventsActivity的活动上的RecyclerView从Firebase数据库获取数据。问题是，当我的主要活动启动MyOrganisedEventsActivity时，没有对方法onCreateViewHolder进行调用，因此RecycleView是空的

但是，在等待片刻，然后锁定和解锁我的手机后，会打电话给onCreateViewHolder，列表项开始出现在RecyclerView上。在活动首次启动时，是否有强制呼叫的方法？或者我的代码有问题吗？我该如何修复它

以下是我目前的代码：

MyOrganisedEventActivity.java：

package com.llawl.tristonpang.intheloop;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

public class MyOrganisedEventsActivity extends AppCompatActivity {
    private RecyclerView mRecyclerView;
    private OrganisedEventsAdapter mAdapter;
    private RecyclerView.LayoutManager mLayoutManager;
    private List<EventInfo> mEventsDataset;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_my_organised_events);
        mRecyclerView = (RecyclerView) findViewById(R.id.org_recycler_view);

        // use this setting to improve performance if you know that changes
        // in content do not change the layout size of the RecyclerView
        mRecyclerView.setHasFixedSize(true);

        // use a linear layout manager
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);

        //mRecyclerView.setItemAnimator(new DefaultItemAnimator());

        mEventsDataset = new ArrayList<>();

        // specify an adapter (see also next example)
        mAdapter = new OrganisedEventsAdapter(mEventsDataset);
        mRecyclerView.setAdapter(mAdapter);

        prepareEventsData();
    }

    private void prepareEventsData() {
        final String currentUser = FirebaseAuth.getInstance().getCurrentUser().getEmail();
        Log.d("InTheLoop", "prepareEventsData(), currentUser = " + currentUser);
        FirebaseDatabase.getInstance().getReference().child("events_info").addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                    //EventInfo event = snapshot.getValue(EventInfo.class);
                    HashMap<String,String> data = (HashMap) snapshot.getValue();
                    //Log.d("InTheLoop", "Event name: " + event.getName());
                    //if (event.getOrganiser().equals(currentUser)) {
                    if (data.get("organiser").equals(currentUser)) {
                        Log.d("InTheLoop", "Adding event: " + data.get("name"));
                        EventInfo event = new EventInfo(data.get("name"), data.get("date"), data.get("time"), data.get("venue"),
                                data.get("desc"), data.get("imageName"), data.get("organiser"));
                        mEventsDataset.add(event);
                    }



                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
        mAdapter.notifyDataSetChanged();

    }
}

Organized_event_row.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/single_event_row"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="?android:attr/selectableItemBackground"
    android:clickable="true"
    android:focusable="true"
    android:orientation="vertical"
    android:paddingBottom="@dimen/row_padding_vertical"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/row_padding_vertical">

    <TextView
        android:id="@+id/org_row_name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:text="name"
        android:textColor="@color/black"
        android:textSize="16sp"
        android:textStyle="bold" />

    <TextView
        android:id="@+id/org_row_venue"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/org_row_name"
        android:text="venue" />

    <TextView
        android:id="@+id/org_row_date"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:text="date"
        android:textColor="@color/black" />

</RelativeLayout>

活动_my_organized_events.xml：

<?xml version="1.0" encoding="utf-8"?>
<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="match_parent"
    android:layout_height="match_parent"
    tools:context=".MyOrganisedEventsActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/org_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</android.support.constraint.ConstraintLayout>

---

非常感谢您的帮助！谢谢

Move

mAdapter.notifyDataSetChanged（）内部
onDataChange（DataSnapshot DataSnapshot）
。您错过了异步调用的本质

 FirebaseDatabase.getInstance().getReference().child("events_info").addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                // Build data here
            }
            mAdapter.notifyDataSetChanged();
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

调用
mAdapter.notifyDataSetChanged（）列表中添加数据后，在
循环中添加数据

因此，基本上是在数据结构中添加数据，然后通知适配器使用新数据更新自身。
您在错误的位置调用了
notifyDataSetChanged（）
。实际上，当适配器中的数据发生更改时，而不是从firebase请求数据时，应该调用它；方法在调用OrganizedEventsAdapter（构造函数）后调用。所以您的mEventsDataset对象为null，并且您将该对象发送到构造函数中。这是可能的。
<?xml version="1.0" encoding="utf-8"?>
<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="match_parent"
    android:layout_height="match_parent"
    tools:context=".MyOrganisedEventsActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/org_recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</android.support.constraint.ConstraintLayout>

 FirebaseDatabase.getInstance().getReference().child("events_info").addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                // Build data here
            }
            mAdapter.notifyDataSetChanged();
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });