问题描述
我为Android Studio中的某个项目开发了Twitter / Instagram之类的社交媒体应用程序，因此在Firebase数据库中搜索用户时遇到问题。我正在使用一个片段，一个适配器和一个用户模型来解决此问题。但是每次Logcat都会向我显示此异常。我尝试了许多不同的解决方案，但没有任何效果。我已经完成了YouTube教程。在他的教程中，一切正常。谢谢您的帮助！
我们正在使用实时Firebase数据库：
我的模型类：User.java
package com.example.neighborhood.Model;
public class User {
private String id;
private String username;
private String imgurl;
private String location;
private String desc;
private String sex;
private String age;
public User (String id,String username,String imgurl,String location,String desc,String sex,String age)
{
this.id = id;
this.username = username;
this.imgurl = imgurl;
this.location = location;
this.desc = desc;
this.sex = sex;
this.age = age;
}
public User() {
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getimgurl() {
return imgurl;
}
public void setimgurl(String imageurl) {
this.imgurl = imageurl;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public String getDesc() {
return desc;
}
public void setDesc(String desc) {
this.desc = desc;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
}
我的用户适配器类：UserAdapter.java
package com.example.neighborhood.Adapter;
import android.content.Context;
import android.content.SharedPreferences;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.fragment.app.FragmentActivity;
import androidx.recyclerview.widget.RecyclerView;
import com.bumptech.glide.Glide;
import com.example.neighborhood.Fragment.ProfileFragment;
import com.example.neighborhood.Model.User;
import com.example.neighborhood.R;
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 java.util.List;
import de.hdodenhof.circleimageview.CircleImageView;
public class UserAdapter extends RecyclerView.Adapter<UserAdapter.ViewHolder>{
private Context mContext;
private List<User> mUsers;
private FirebaseUser firebaseUser;
private FirebaseDatabase database;
private DatabaseReference userRef;
private static final String USER = "Users";
public UserAdapter(Context mContext,List<User> mUsers)
{
this.mContext = mContext;
this.mUsers = mUsers;
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup,int i) {
View view = LayoutInflater.from(mContext).inflate(R.layout.user_item,viewGroup,false);
return new UserAdapter.ViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull final ViewHolder viewHolder,final int i) {
firebaseUser = FirebaseAuth.getInstance().getCurrentUser();
final User user = mUsers.get(i);
viewHolder.btn_follow.setVisibility(View.VISIBLE);
viewHolder.username.setText(user.getUsername());
Glide.with(mContext).load(user.getimgurl()).into(viewHolder.image_profile);
friendRequest(user.getId(),viewHolder.btn_follow);
if (user.getId().equals(firebaseUser.getUid()))
{
viewHolder.btn_follow.setVisibility(View.GONE);
}
viewHolder.itemView.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
SharedPreferences.Editor editor = mContext.getSharedPreferences("PREFS",Context.MODE_PRIVATE).edit();
editor.putString("profileid",user.getId());
editor.apply();
((FragmentActivity)mContext).getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container,new ProfileFragment()).commit();
}
});
viewHolder.btn_follow.setonClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
if (viewHolder.btn_follow.getText().toString().equals("Freundschaftsanfrage"))
{
FirebaseDatabase.getInstance().getReference().child("Unbefreundet").child(firebaseUser.getUid()).child("Befreundet").child(user.getId()).setValue(true);
FirebaseDatabase.getInstance().getReference().child("Unbefreundet").child(user.getId()).child("Follower").child(firebaseUser.getUid()).setValue(true);
}
else
{
FirebaseDatabase.getInstance().getReference().child("Unbefreundet").child(firebaseUser.getUid()).child("Befreundet").child(user.getId()).removeValue();
FirebaseDatabase.getInstance().getReference().child("Unbefreundet").child(user.getId()).child("Follower").child(firebaseUser.getUid()).removeValue();
}
}
});
}
@Override
public int getItemCount() {
return mUsers.size();
}
public class ViewHolder extends RecyclerView.ViewHolder{
public TextView username;
public CircleImageView image_profile;
public Button btn_follow;
public ViewHolder(@NonNull View itemView)
{
super(itemView);
username = itemView.findViewById(R.id.username);
image_profile = itemView.findViewById(R.id.image_profile);
btn_follow = itemView.findViewById(R.id.btn_friendRequest);
}
}
private void friendRequest(final String userid,final Button button)
{
DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Unbefreundet").child(firebaseUser.getUid()).child("Befreundet");
reference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
if (snapshot.child(userid).exists())
{
button.setText("Befreundet");
}
else
{
button.setText("Freundschaftsanfrage");
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
}
我的FriendFragment类：FriendFragment.java
package com.example.neighborhood.Fragment;
import androidx.annotation.NonNull;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.linearlayoutmanager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.widget.ImageButton;
import com.example.neighborhood.Adapter.UserAdapter;
import com.example.neighborhood.Model.User;
import com.example.neighborhood.R;
import com.google.firebase.auth.FirebaseAuth;
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.Query;
import com.google.firebase.database.ValueEventListener;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
public class FriendFragment extends Fragment {
private RecyclerView recyclerView;
private UserAdapter userAdapter;
private List<User> mUsers;
private ImageButton search_btn;
EditText search_bar;
@Override
public View onCreateView (LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.fragment_friend,container,false);
recyclerView = view.findViewById(R.id.recycler_view);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new linearlayoutmanager(getContext()));
search_btn = view.findViewById(R.id.search);
search_bar = view.findViewById(R.id.search_bar);
mUsers = new ArrayList<>();
userAdapter = new UserAdapter(getContext(),mUsers);
recyclerView.setAdapter(userAdapter);
recyclerView.setAdapter(userAdapter);
readUsers();
search_bar.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence charSequence,int i,int i1,int i2) {
}
@Override
public void onTextChanged(CharSequence charSequence,int i2) {
searchUsers(charSequence.toString().toLowerCase());
}
@Override
public void afterTextChanged(Editable editable) {
}
});
return view;
}
private void searchUsers (String s)
{
Query query = FirebaseDatabase.getInstance().getReference("Users").orderByChild("username")
.startAt(s)
.endAt(s+"\uf8ff");
query.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
mUsers.clear();
for (DataSnapshot snapshot : dataSnapshot.getChildren())
{
User user = snapshot.getValue(User.class);
mUsers.add(user);
}
userAdapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}
public void readUsers(){
DatabaseReference reference = FirebaseDatabase.getInstance().getReference("Users");
reference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
if ( search_bar.getText().toString().equals("")) {
mUsers.clear();
for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()){
User user = dataSnapshot1.getValue(User.class);
mUsers.add(user);
}
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
}
}
例外：
2020-08-11 21:08:39.600 25370-25370/com.example.neighborhood E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.neighborhood,PID: 25370
com.google.firebase.database.DatabaseException: Failed to convert value of type java.util.HashMap to String
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertString(CustomClassMapper.java:425)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializetoClass(CustomClassMapper.java:216)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializetoType(CustomClassMapper.java:178)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.access$100(CustomClassMapper.java:47)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.deserialize(CustomClassMapper.java:592)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.deserialize(CustomClassMapper.java:562)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(CustomClassMapper.java:432)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializetoClass(CustomClassMapper.java:231)
at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(CustomClassMapper.java:79)
at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203)
at com.example.neighborhood.Fragment.FriendFragment$3.onDataChange(FriendFragment.java:112)
at com.google.firebase.database.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:75)
at com.google.firebase.database.core.view.DataEvent.fire(DataEvent.java:63)
at com.google.firebase.database.core.view.EventRaiser$1.run(EventRaiser.java:55)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:223)
at android.app.ActivityThread.main(ActivityThread.java:7523)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:941)
解决方法
暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！
如果你已经找到好的解决方法，欢迎将解决方案带上本链接一起发送给小编。
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