如何将 Firebase 数据提取到数组中以进行 recyclerview？
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【中文标题】如何将 Firebase 数据提取到数组中以进行 recyclerview？【英文标题】：How to fetch Firebase data into arrays for recyclerview? 【发布时间】：2018-09-17 04:46:06 【问题描述】：这是我的 HomeActivity
package my.unimas.a50200siswa.studentattendancemonitoringsystem;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
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.ArrayList;
import java.util.List;
public class HomeActivity extends AppCompatActivity
String userID;
List<CourseModel> mlist;
TextView btnSignOut, UserName;
RecyclerView courseRecycler;
String CourseCode, CourseName;
/*---- Firebase Database stuff ----*/
FirebaseDatabase mFirebaseDatabase;
FirebaseAuth mAuth;
FirebaseUser user;
FirebaseAuth.AuthStateListener mAuthListener;
DatabaseReference myRef;
@Override
protected void onStart()
super.onStart();
mAuth.addAuthStateListener(mAuthListener);
@Override
public void onStop()
super.onStop();
if (mAuthListener != null)
mAuth.removeAuthStateListener(mAuthListener);
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_home);
/*-------Finding View---------*/
Button btnShow = findViewById(R.id.show);
btnSignOut = (TextView) findViewById(R.id.btnsignout_home);
UserName = findViewById(R.id.username);
courseRecycler = findViewById(R.id.recyclerviewcourse);
btnSignOut.setOnClickListener(new View.OnClickListener()
@Override
public void onClick(View v)
mAuth.signOut();
);
mAuthListener = new FirebaseAuth.AuthStateListener()
@Override
public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth)
if (firebaseAuth.getCurrentUser() == null)
startActivity(new Intent(HomeActivity.this, SignInActivity.class));
;
/* ----------------- Firebase Elements -----------------*/
mAuth = FirebaseAuth.getInstance();
user = mAuth.getCurrentUser();
userID = user.getUid();
mFirebaseDatabase = FirebaseDatabase.getInstance();
myRef = mFirebaseDatabase.getInstance().getReference();
UserName.setText(user.getDisplayName());
/*------------------------------------------------------------------*/
myRef.addValueEventListener(new ValueEventListener()
@Override
public void onDataChange(DataSnapshot dataSnapshot)
// This method is called once with the initial value and again
// whenever data at this location is updated.
mlist = new ArrayList<CourseModel>();
for (DataSnapshot dataSnapshot1 : dataSnapshot.child("Users").child(userID).child("Courses").getChildren())
CourseModel value = dataSnapshot1.getValue(CourseModel.class);
CourseModel course = new CourseModel();
String userID = value.getUserId();
course.setUserId(userID);
String courseCode = value.getCourseCode();
course.setCourseCode(courseCode);
for (DataSnapshot dataSnapshot2 : dataSnapshot1.child("CourseName").getChildren())
CourseModel value2 = dataSnapshot2.getValue(CourseModel.class);
String courseName = value2.getCourseName();
course.setCourseName(courseName);
mlist.add(course);
@Override
public void onCancelled(DatabaseError error)
// Failed to read value
Log.w("Hello", "Failed to read value.", error.toException());
);
RecyclerViewAdapterCourse recyclerAdapter = new RecyclerViewAdapterCourse(mlist, HomeActivity.this);
RecyclerView.LayoutManager recycler = new GridLayoutManager(HomeActivity.this, 2);
/// RecyclerView.LayoutManager recyce = new LinearLayoutManager(MainActivity.this);
// recycle.addItemDecoration(new GridSpacingItemDecoration(2, dpToPx(10), true));
courseRecycler.setLayoutManager(recycler);
courseRecycler.setItemAnimator(new DefaultItemAnimator());
courseRecycler.setAdapter(recyclerAdapter);
这是我的 RecyclerViewCourse.class
package my.unimas.a50200siswa.studentattendancemonitoringsystem;
import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import java.util.List;
class RecyclerViewAdapterCourse extends RecyclerView.Adapter<RecyclerViewAdapterCourse.CourseViewHolder>
private Context mContext ;
private List<CourseModel> mlist ;
public RecyclerViewAdapterCourse(List<CourseModel> mData, Context mContext)
this.mContext = mContext;
this.mlist = mData;
@Override
public CourseViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
View view =LayoutInflater.from(mContext).inflate(R.layout.item_course,parent,false);
CourseViewHolder courseViewHolder = new CourseViewHolder(view);
return courseViewHolder;
@Override
public void onBindViewHolder(CourseViewHolder holder, int position)
CourseModel courselist = mlist.get(position);
holder.userID.setText(courselist.getUserId());
holder.courseCode.setText(courselist.getCourseCode());
holder.courseName.setText(courselist.getCourseName());
@Override
public int getItemCount()
int arr = 0;
try
if(mlist.size()==0)
arr = 0;
else
arr=mlist.size();
catch (Exception e)
return arr;
class CourseViewHolder extends RecyclerView.ViewHolder
TextView userID,courseCode,courseName;
public CourseViewHolder(View itemView)
super(itemView);
userID = (TextView) itemView.findViewById(R.id.userid);
courseCode= (TextView) itemView.findViewById(R.id.coursecode);
courseName= (TextView) itemView.findViewById(R.id.coursename);
这是我的 CourseModel.class
package my.unimas.a50200siswa.studentattendancemonitoringsystem;
public class CourseModel
public String UserId, CourseCode, CourseName;
public String getUserId()
return UserId;
public String getCourseCode()
return CourseCode;
public String getCourseName()
return CourseName;
public void setUserId(String userid)
this.UserId = userid;
public void setCourseCode(String coursecode)
this.CourseCode = coursecode;
public void setCourseName(String coursename)
this.CourseCode = coursename;
我想要这样的数组列表：
"***", "TMI4013", "System Programming"
"***", "TMI4033", "LogicProgramming"
我对数组中的 Firebase 数据检索并不是很熟悉。我尝试了许多发布在堆栈中的答案。没有工作。在某些答案中，有时它会在一段时间后显示数据，然后在实时数据库中数据被删除，我什至不明白为什么。
我没有提供 XML 文件，因为我尝试使用本地文件并在 HomeActivity 中生成数组并且效果很好。
mlist = new ArrayList<>();
mlist.add(new CourseModel("012223","TMN4013","System Programming"));
mlist.add(new CourseModel("34566","TMN4013","System Programming"));
RecyclerView myrv = (RecyclerView) findViewById(R.id.recyclerview_id);
RecyclerViewAdapter myAdapter = new RecyclerViewAdapter(this,mlist);
myrv.setLayoutManager(new GridLayoutManager(this,3));
myrv.setAdapter(myAdapter);
【问题讨论】：
请添加您的 Firebase 数据库的屏幕截图 @Nuwan94 我已经添加了。请点击链接说“我想要像 ........这样的数组列表” 您需要从 firebase 获取数据并显示在 recyclerView 上吗？我说的对吗？ @SarasaGunawardhana 是的.. RecyclerViewAdapterCourse recyclerAdapter = new RecyclerViewAdapterCourse(mlist, HomeActivity.this); RecyclerView.LayoutManager recycler = new GridLayoutManager(HomeActivity.this, 2); courseRecycler.setLayoutManager(recycler); courseRecycler.setItemAnimator(new DefaultItemAnimator()); courseRecycler.setAdapter(recyclerAdapter); 如果您有兴趣，this 是您可以从 Firebase 实时数据库中检索数据并使用FirebaseRecyclerAdapter 将其显示在 RecyclerView 中的方法。
【参考方案1】：
从 firebase 中检索数据并将列表转换为这样的数组
for (DataSnapshot dataSnapshot1 : dataSnapshot.child("Users").child(userID).child("Courses").getChildren())
CourseModel value = dataSnapshot1.getValue(CourseModel.class);
CourseModel course = new CourseModel();
String userID = value.getUserId(); course.setUserId(userID);
String courseCode = value.getCourseCode();
course.setCourseCode(courseCode);
for (DataSnapshot dataSnapshot2 : dataSnapshot1.child("CourseName").getChildren())
CourseModel value2 = dataSnapshot2.getValue(CourseModel.class);
String courseName = value2.getCourseName();
course.setCourseName(courseName);
mlist.add(course);
CourseModel[] array = mlist.toArray(new CourseModel[mlist.size()]);
编辑：
像这样改变你的适配器
RecyclerViewAdapter myAdapter = new RecyclerViewAdapter(this, array);
将recyclerView的构造函数改为CourseModel数组
public RecyclerViewAdapterCourse(CourseModel[] mData, Context mContext)
this.mContext = mContext;
this.mArray = mData;
@Override
public void onBindViewHolder(CourseViewHolder holder, int position)
CourseModel courselist = marray[position];
holder.userID.setText(courselist.getUserId());
holder.courseCode.setText(courselist.getCourseCode());
holder.courseName.setText(courselist.getCourseName());
【讨论】：
感谢您的回复。它显示在应该找到 CourseModel[] 的位置查找 odject 时出错。然后我怎样才能将它传递给我在 recyclerview 中的上下文？ 侯赛因谢谢你再次显示同样的错误，即使根据你的建议更正后。 错误：不兼容的类型：Object[] 无法转换为 CourseModel[] 错误：不兼容的类型：HomeActivity 无法转换为 CourseModel[] 检查编辑的答案。这将解决您的问题以上是关于如何将 Firebase 数据提取到数组中以进行 recyclerview？的主要内容，如果未能解决你的问题，请参考以下文章
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