我有一些代码，其功能是在RecyclerView中显示用户的姓名和年龄，但是无论我放在哪里，相同的RecyclerView总是返回null。
我试图将getUserInfo（）放在onStart（）中，但是它没有用。
我已经看过StackOverflow中的其他帖子，但仍然没有用。
我的 MainActivity.java
package com.pap.diogo.pilltrack;
import android.accounts.Account;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.text.Layout;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.RelativeLayout;
import android.widget.TextView;
import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
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 org.w3c.dom.Text;
public class MainActivity extends AppCompatActivity {
private RelativeLayout pills_layout, appoint_layout, add_pills_layout, add_appoints_layout, account_layout, add_button;
private View pills, appointments, add_pills, add_appoints, account;
private TextView AccountName0, AccountAge0;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_home:
Home();
return true;
case R.id.navigation_pills:
Pills();
return true;
case R.id.navigation_appointment:
Appointment();
return true;
case R.id.navigation_account:
Account();
return true;
}
return false;
}
};
public MainActivity() {
}
private void Account(){
RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) add_button.getLayoutParams();
params.addRule(RelativeLayout.BELOW, R.id.account);
pills_layout.removeView(pills);
appoint_layout.removeView(appointments);
add_pills_layout.removeView(add_pills);
add_appoints_layout.removeView(add_appoints);
//account_layout.removeAllViews();
//account_layout.addView(account);
add_button.setVisibility(View.VISIBLE);
getUserInfo();
}
private void Appointment() {
RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) add_button.getLayoutParams();
params.addRule(RelativeLayout.BELOW, R.id.add_appoints);
pills_layout.removeView(pills);
appoint_layout.removeView(appointments);
add_pills_layout.removeView(add_pills);
//account_layout.removeView(account);
add_appoints_layout.removeAllViews();
add_appoints_layout.addView(add_appoints);
add_button.setVisibility(View.VISIBLE);
}
private void Pills() {
RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams) add_button.getLayoutParams();
params.addRule(RelativeLayout.BELOW, R.id.add_pills);
pills_layout.removeView(pills);
appoint_layout.removeView(appointments);
add_appoints_layout.removeView(add_appoints);
//account_layout.removeView(account);
add_pills_layout.removeAllViews();
add_pills_layout.addView(add_pills);
add_button.setVisibility(View.VISIBLE);
}
private void Home() {
add_appoints_layout.removeView(add_appoints);
add_pills_layout.removeView(add_pills);
//account_layout.removeView(account);
pills_layout.removeAllViews();
pills_layout.addView(pills);
appoint_layout.removeAllViews();
appoint_layout.addView(appointments);
add_button.setVisibility(View.GONE);
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
pills_layout = findViewById(R.id.pills_layout);
appoint_layout = findViewById(R.id.appoint_layout);
add_pills_layout = findViewById(R.id.add_pills);
add_appoints_layout = findViewById(R.id.add_appoints);
//account_layout = findViewById(R.id.account);
add_button = findViewById(R.id.add);
AccountName0 = findViewById(R.id.AccountName0);
AccountAge0 = findViewById(R.id.AccountAge0);
LayoutInflater inflater = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
pills = inflater.inflate(R.layout.pills, null);
appointments = inflater.inflate(R.layout.appointments, null);
add_pills = inflater.inflate(R.layout.add_pills, null);
add_appoints = inflater.inflate(R.layout.add_appoint, null);
account = inflater.inflate(R.layout.account, null);
pills_layout.addView(pills);
appoint_layout.addView(appointments);
add_button.setVisibility(View.GONE);
BottomNavigationView navigation = findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}
public void getUserInfo(){
RecyclerView accountUsers;
if ((accountUsers = account.findViewById(R.id.AccountList)) != null)
{
accountUsers.setHasFixedSize(true);
accountUsers.setLayoutManager(new LinearLayoutManager(getBaseContext()));
FirebaseUser user = FirebaseAuth.getInstance().getCurrentUser();
final String userid = user.getUid();
final DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Users");
FirebaseRecyclerOptions<AccountLayout> AccountQ = new FirebaseRecyclerOptions.Builder<AccountLayout>().setQuery(ref, AccountLayout.class).setLifecycleOwner(this).build();
FirebaseRecyclerAdapter<AccountLayout, AccountInfo> AccountAdapter = new FirebaseRecyclerAdapter<AccountLayout, AccountInfo>(AccountQ){
@NonNull
@Override
public AccountInfo onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
return new AccountInfo(LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.account_layout, viewGroup, false));
}
@Override
protected void onBindViewHolder(@NonNull final AccountInfo holder, int position, @NonNull final AccountLayout model) {
ref.child(userid).addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
final String name = dataSnapshot.child("name").getValue().toString();
final String age = dataSnapshot.child("idade").getValue().toString();
holder.setName(name);
holder.setAge(age);
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
};
accountUsers.setAdapter(AccountAdapter);
}
}
public static class AccountInfo extends RecyclerView.ViewHolder{
View AccountL;
public AccountInfo(@NonNull View itemView) {
super(itemView);
AccountL = itemView;
}
public void setName(String name){
TextView AccountName = AccountL.findViewById(R.id.AccountName0);
AccountName.setText(name);
}
public void setAge(String age){
TextView AccountAge = AccountL.findViewById(R.id.AccountAge0);
AccountAge.setText(age);
}
}
}
我的 AccountLayout.java
package com.pap.diogo.pilltrack;
public class AccountLayout {
private String name, idade;
public AccountLayout() {
}
public AccountLayout(String name, String idade) {
this.name = name;
this.idade = idade;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getIdade() {
return idade;
}
public void setIdade(String idade) {
this.idade = idade;
}
}
我的 account.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
android:layout_height="match_parent">
<android.support.v7.widget.RecyclerView
android:id="@+id/AccountList"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</android.support.v7.widget.RecyclerView>
</RelativeLayout>
答案 0 :(得分：0)
如下修改您的代码：
public void getUserInfo(){
RecyclerView accountUsers = (RecyclerView) account.findViewById(R.id.AccountList);
if (accountUsers != null)
{
...