Android addListenerForSingleValueEvent未执行
addListenerForSingleValueEvent根本未执行。运行调试器时,它不会从数据库中提取数据。我甚至试过addValueEventListener,但没有用 我已经为片段添加了代码,我正试图在其上执行此操作Android addListenerForSingleValueEvent未执行,android,database,firebase,firebase-realtime-database,Android,Database,Firebase,Firebase Realtime Database,addListenerForSingleValueEvent根本未执行。运行调试器时,它不会从数据库中提取数据。我甚至试过addValueEventListener,但没有用 我已经为片段添加了代码,我正试图在其上执行此操作 package com.example.visan.peds; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v7.widget.Linea
package com.example.visan.peds;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.List;
public class Landing_mother extends Fragment {
private List<Ailment> ailments;
private RecyclerView recyclerView;
LinearLayoutManager layoutManager;
private RecyclerView.Adapter adapter;
public Landing_mother(){}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final View view=inflater.inflate(R.layout.fragment_landing_mother,container,false);
ailments=new ArrayList<>();
recyclerView =(RecyclerView)view.findViewById(R.id.recyclerView1);
recyclerView.setHasFixedSize(true);
layoutManager=new LinearLayoutManager(getActivity());
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutManager);
getData();
adapter=new LandingAdapter(ailments,getActivity());
recyclerView.setAdapter(adapter);
return view;
}
private void getData(){
FirebaseDatabase db=FirebaseDatabase.getInstance();
DatabaseReference ref=db.getReference().child("Mother");
if(ref!=null){
ref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
if (dataSnapshot.exists()){
Ailment ailment=new Ailment();
for (int i=0;i<dataSnapshot.getChildrenCount();i++){
String img=dataSnapshot.child(Integer.toString(i)).child("img").getValue(String.class);
ailment.setImage_url(img);
String name=dataSnapshot.child(Integer.toString(i)).child("name").getValue(String.class);
ailment.setName(name);
ailments.add(ailment);
}
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}else {
Toast.makeText(getActivity(),"Reference not obtained",Toast.LENGTH_SHORT).show();
}
}
}
package com.example.visan.peds;
导入android.os.Bundle;
导入android.support.v4.app.Fragment;
导入android.support.v7.widget.LinearLayoutManager;
导入android.support.v7.widget.RecyclerView;
导入android.view.LayoutInflater;
导入android.view.view;
导入android.view.ViewGroup;
导入android.widget.Toast;
导入com.google.firebase.database.DataSnapshot;
导入com.google.firebase.database.DatabaseError;
导入com.google.firebase.database.DatabaseReference;
导入com.google.firebase.database.FirebaseDatabase;
导入com.google.firebase.database.ValueEventListener;
导入java.util.ArrayList;
导入java.util.List;
公共类登录\u母亲扩展片段{
私人名单疾病;
私人回收站;
直线布局经理布局经理;
专用循环视图适配器;
公共登陆{}
@凌驾
创建时的公共void(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
}
@凌驾
创建视图上的公共视图(布局、充气机、视图组容器、,
Bundle savedInstanceState){
最终视图=充气机。充气(右布局。碎片着陆母亲,容器,假);
疾病=新的ArrayList();
recyclerView=(recyclerView)view.findViewById(R.id.RecyclerViewW1);
recyclerView.setHasFixedSize(true);
layoutManager=新的LinearLayoutManager(getActivity());
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutManager);
getData();
适配器=新的着陆适配器(疾病,getActivity());
recyclerView.setAdapter(适配器);
返回视图;
}
私有void getData(){
FirebaseDatabase db=FirebaseDatabase.getInstance();
DatabaseReference=db.getReference().child(“母亲”);
如果(ref!=null){
ref.addListenerForSingleValueEvent(新的ValueEventListener(){
@凌驾
公共void onDataChange(DataSnapshot DataSnapshot){
if(dataSnapshot.exists()){
疾病=新的疾病();
对于(inti=0;i请注意,onDataChange不是主流的一部分并假设正在立即从数据库中检索值,然后设置适配器。但实际上,onDataChange可能稍后启动。请尝试在onDataChange方法中使用setadapter或notifydatasethaschanged