Recyclerview在firebase中多次调用函数时一次又一次地显示数据答案

【问题标题】：Recyclerview show data again and again when call function multiple times in firebaseRecyclerview在firebase中多次调用函数时一次又一次地显示数据
【发布时间】：2020-06-28 20:09:29
【问题描述】：

最近我正在使用 firebase 开发 android 项目，我正在使用 recyclerview 来显示数据。我添加了编辑文本和搜索按钮，当我们单击搜索按钮时，会调用一个函数并显示其搜索相关数据。但问题是，当我单击搜索按钮时，它会显示数据（假设只找到 1 个结果），当我再次单击搜索按钮时，它会再次附加相同的数据，当我单击按钮时它会一次又一次地显示。

我真的很担心，请告诉我是什么问题。

我的适配器代码


import android.app.LauncherActivity;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.squareup.picasso.Picasso;

import java.util.ArrayList;

public class Find_donor_Adapter extends RecyclerView.Adapter<Find_donor_Adapter.MyViewHolder> {

    Context context;
    ArrayList<find_donor_helper> find_donor_helper;

    public Find_donor_Adapter(Context context, ArrayList<find_donor_helper> find_donor_helper) {
        this.context = context;
        this.find_donor_helper = find_donor_helper;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.find_blood_layout,parent,false));
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

        final find_donor_helper helper = find_donor_helper.get(position);
        holder.lname.setText(find_donor_helper.get(position).getFullname());
        holder.bldgrp.setText(find_donor_helper.get(position).getBloodgroup());

        final String n = helper.getPhonenumber();
        holder.lnumber.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                try
                {
                    Intent call = new Intent(Intent.ACTION_CALL);
                    call.setData(Uri.parse("tel:03465987599"));
                    call.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                    context.startActivity(call);
                }
                catch (Exception e)
                {
                    Toast.makeText(context, ""+e.getMessage(), Toast.LENGTH_LONG).show();
                }
            }
        });

        holder.ucall.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent call = new Intent(Intent.ACTION_VIEW);
                call.setData(Uri.parse("sms:"+n));
                call.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                context.startActivity(call);
            }
        });



        Picasso.get().load(helper.getUserimg()).into(holder.uimg);
    }

    @Override
    public int getItemCount() {
        return find_donor_helper.size();
    }

    public class MyViewHolder extends RecyclerView.ViewHolder{

        TextView lname,bldgrp;
        Button lnumber,ucall;
        ImageView uimg;
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            lname = (TextView) itemView.findViewById(R.id.name);
            bldgrp = (TextView) itemView.findViewById(R.id.bloodgroup);
            lnumber = (Button) itemView.findViewById(R.id.number);
            uimg = (ImageView) itemView.findViewById(R.id.userimg);
            ucall = (Button) itemView.findViewById(R.id.call);
        }
    }
}

主要代码


import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.app.ProgressDialog;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Toast;

import com.google.firebase.database.ChildEventListener;
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;

public class Find_BloodDonator extends AppCompatActivity {

    RecyclerView findblood;
    ArrayList<find_donor_helper> arrayList;
    Find_donor_Adapter adapter;
    ProgressDialog pd;

    EditText searchtext;
    String st;
    DatabaseReference reference;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_find__blood_donator);

        pd = new ProgressDialog(this);
        pd.setMessage("Please wait...");
        pd.setCanceledOnTouchOutside(false);
        pd.setCancelable(false);


        findblood = findViewById(R.id.findblood);

        findblood.setLayoutManager(new LinearLayoutManager(this));

        arrayList = new ArrayList<find_donor_helper>();

        //alldata("blooddonor","Yes");


        searchtext = findViewById(R.id.searchtext);
        st = searchtext.getText().toString();

        searchtext.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence s, int start, int count, int after) {
                alldata("bloodgroup","hello");
            }

            @Override
            public void onTextChanged(CharSequence s, int start, int before, int count) {
                alldata("bloodgroup","hello");
            }

            @Override
            public void afterTextChanged(Editable s) {
                alldata("bloodgroup",s.toString());
            }
        });


    }

    private void alldata(String blooddonor,String bloodgroup) {

        reference = FirebaseDatabase.getInstance().getReference().child("Users");

        Query chk = reference.limitToLast(10).orderByChild(blooddonor).equalTo(bloodgroup);

        chk.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

                pd.cancel();

                try {
                    for (DataSnapshot dataSnapshot1:dataSnapshot.getChildren())
                    {
                        find_donor_helper donor_helper = dataSnapshot1.getValue(find_donor_helper.class);
                        arrayList.add(donor_helper);
                    }
                    adapter = new Find_donor_Adapter(getApplicationContext(),arrayList);
                    findblood.setAdapter(adapter);
                }
                catch (Exception e)
                {
                    pd.cancel();
                    Toast.makeText(Find_BloodDonator.this, ""+e.getMessage(), Toast.LENGTH_SHORT).show();
                }

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                pd.cancel();
                Toast.makeText(Find_BloodDonator.this, "Server error", Toast.LENGTH_SHORT).show();
            }
        });
    }

}

【问题讨论】：

在点击功能上添加搜索按钮的代码
@CyberShark 我添加了edittext功能代码
最近我改了代码...当editext文本更改函数调用并显示结果...
不要在每次搜索文本更改时更改适配器，而是尝试通知数据集更改
我试过了，但没有运气。它显示重复:(

标签： java android android-studio firebase-realtime-database android-recyclerview

【解决方案1】：

当您进行新搜索时，您的 onDataChange 会被调用并包含所有搜索结果。然后，您当前将这些搜索结果添加到 arrayList，这意味着当您执行其他搜索时，列表只会越来越长。

要仅显示最新查询的结果，您需要先清除arrayList，然后再将新的搜索结果添加到其中：

Query chk = reference.limitToLast(10).orderByChild(blooddonor).equalTo(bloodgroup);

chk.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        pd.cancel();
        arrayList.clear()
        try {
            for (DataSnapshot dataSnapshot1:dataSnapshot.getChildren()) {
                find_donor_helper donor_helper = dataSnapshot1.getValue(find_donor_helper.class);
                arrayList.add(donor_helper);
            }
            adapter = new Find_donor_Adapter(getApplicationContext(),arrayList);
            findblood.setAdapter(adapter);
        }
        catch (Exception e) {
            pd.cancel();
            Toast.makeText(Find_BloodDonator.this, ""+e.getMessage(), Toast.LENGTH_SHORT).show();
        }

    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        pd.cancel();
        Toast.makeText(Find_BloodDonator.this, "Server error", Toast.LENGTH_SHORT).show();
    }
});

请注意，您无需在每次更改 arrayList 时都创建新适配器。您还可以修改 arrayList 以包含最新项目（就像您已经做的那样），然后简单地告诉现有适配器使用更新的数据刷新其视图。

这意味着您可以将适配器的创建移动到您的onCreate：

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_find__blood_donator);

    ...

    arrayList = new ArrayList<find_donor_helper>();

    adapter = new Find_donor_Adapter(getApplicationContext(),arrayList);
    findblood.setAdapter(adapter);

然后刷新数据：

Query chk = reference.limitToLast(10).orderByChild(blooddonor).equalTo(bloodgroup);

chk.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        pd.cancel();
        arrayList.clear()
        try {
            for (DataSnapshot dataSnapshot1:dataSnapshot.getChildren()) {
                find_donor_helper donor_helper = dataSnapshot1.getValue(find_donor_helper.class);
                arrayList.add(donor_helper);
            }
            adapter.notifyDataSetChanged();
        }
        catch (Exception e) {
            pd.cancel();
            Toast.makeText(Find_BloodDonator.this, ""+e.getMessage(), Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        pd.cancel();
        Toast.makeText(Find_BloodDonator.this, "Server error", Toast.LENGTH_SHORT).show();
    }
});

【讨论】：