我正在为我的应用开发搜索功能。我对家庭适配器实现了Filterable方法。我的数组列表引发了空指针异常,并且我看到了许多其他类似的问题,其中的问题不是初始化数组列表。但是,我在下面的代码中,但是我不确定其初始化位置是否正确。请为我提供纠正方法的建议。谢谢。
这是我得到的错误:
我的家庭适配器代码如下:
package com.example.oddsynew.Home;
import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.example.oddsynew.Modals.Job;
import com.example.oddsynew.R;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
import java.util.List;
public class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder> implements Filterable {
Context context;
ArrayList<Job> jobs, jobsListFull;
public HomeAdapter(Context c, ArrayList<Job> j) {
context = c;
jobs = j;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.job_row, parent, false));
}
@Override
public void onBindViewHolder(@NonNull final MyViewHolder holder, final int position) {
holder.recruiterName.setText(jobs.get(position).getRecruiter_name());
holder.jobName.setText(jobs.get(position).getJob_name());
holder.jobLocation.setText(jobs.get(position).getLocation());
holder.jobCharge.setText(jobs.get(position).getJob_charge());
Picasso.get().load(jobs.get(position).getProf_pic()).into(holder.profPic);
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
Intent intent = new Intent(context, JobInfo.class);
intent.putExtra("recruiterName", jobs.get(holder.getAdapterPosition()).getRecruiter_name());
intent.putExtra("jobName", jobs.get(holder.getAdapterPosition()).getJob_name());
intent.putExtra("jobCharge", jobs.get(holder.getAdapterPosition()).getJob_charge());
intent.putExtra("jobLocation", jobs.get(holder.getAdapterPosition()).getLocation());
intent.putExtra("profPic", jobs.get(holder.getAdapterPosition()).getProf_pic());
intent.putExtra("startDate", jobs.get(holder.getAdapterPosition()).getStart_date());
intent.putExtra("endDate", jobs.get(holder.getAdapterPosition()).getEnd_date());
intent.putExtra("startTime", jobs.get(holder.getAdapterPosition()).getStart_time());
intent.putExtra("endTime", jobs.get(holder.getAdapterPosition()).getEnd_time());
intent.putExtra("jobDesc", jobs.get(holder.getAdapterPosition()).getJob_desc());
intent.putExtra("jobTasks", jobs.get(holder.getAdapterPosition()).getJob_tasks());
intent.putExtra("addPref", jobs.get(holder.getAdapterPosition()).getAdd_pref());
intent.putExtra("jobID", jobs.get(holder.getAdapterPosition()).getJobID());
context.startActivity(intent);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
@Override
public int getItemCount() {
return jobs.size();
}
@Override
public Filter getFilter() {
return searchFilter;
}
private Filter searchFilter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence constraint) {
ArrayList<Job> filteredList = new ArrayList<>();
if(constraint == null || constraint.length() == 0){
filteredList.addAll(jobsListFull);
}else{
String filterPattern = constraint.toString().toLowerCase().trim();
for(Job job: jobsListFull){
if(job.getJob_name().toLowerCase().contains(filterPattern)){
filteredList.add(job);
}
}
}
FilterResults results = new FilterResults();
results.values = filteredList;
return results;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
jobs.clear();
jobs.addAll((List) results.values);
notifyDataSetChanged();
}
};
class MyViewHolder extends RecyclerView.ViewHolder {
TextView recruiterName, jobName, jobLocation, jobCharge;
ImageView profPic;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
recruiterName = itemView.findViewById(R.id.recruiterName);
jobName = itemView.findViewById(R.id.jobName);
jobLocation = itemView.findViewById(R.id.jobLocation);
jobCharge = itemView.findViewById(R.id.jobCharge);
profPic = itemView.findViewById(R.id.prof_pic);
}
}
public HomeAdapter(ArrayList<Job> jobs) {
this.jobs = jobs;
jobsListFull = new ArrayList<>(jobs);
}
}
这是我的搜索类别:
package com.example.oddsynew;
import android.os.Bundle;
import android.widget.SearchView;
import android.widget.Toast;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import com.example.oddsynew.Home.HomeAdapter;
import com.example.oddsynew.Modals.Job;
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;
public class Search extends AppCompatActivity {
DatabaseReference myRef;
RecyclerView newJobList;
ArrayList<Job> list;
HomeAdapter adapter;
SearchView searchView;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_search);
newJobList = (RecyclerView) findViewById(R.id.jobRecyclerView);
searchView = (SearchView) findViewById(R.id.search);
try {
newJobList.setLayoutManager(new LinearLayoutManager(Search.this));
list = new ArrayList<Job>();
adapter = new HomeAdapter(Search.this, list);
newJobList.setAdapter(adapter);
myRef = FirebaseDatabase.getInstance().getReference().child("Jobs");
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for (DataSnapshot ds : dataSnapshot.getChildren()) {
Job j = ds.getValue(Job.class);
list.add(j);
}
System.out.println(list);
adapter.notifyDataSetChanged();
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
Toast.makeText(Search.this, "Error", Toast.LENGTH_SHORT).show();
}
});
searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
@Override
public boolean onQueryTextSubmit(String query) {
return false;
}
@Override
public boolean onQueryTextChange(String newText) {
adapter.getFilter().filter(newText);
return false;
}
});
} catch (Exception e) {
e.printStackTrace();
}
}
}
SOLUTION:在IntelliJ Amiya's的帮助下,我想到了以下更正的代码。
@Override
public Filter getFilter() {
return searchFilter;
}
private Filter searchFilter = new Filter() {
@Override
protected FilterResults performFiltering(CharSequence charSequence) {
String charString = charSequence.toString();
if (charString.isEmpty()) {
jobs = jobsListFull;
} else {
ArrayList<Job> filteredList = new ArrayList<>();
for (Job row : jobsListFull) {
if (row.getJob_name().toLowerCase().contains(charString.toLowerCase())) {
filteredList.add(row);
}
}
jobs = filteredList;
}
FilterResults filterResults = new FilterResults();
filterResults.values = jobs;
return filterResults;
}
@Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
jobs = ((ArrayList) filterResults.values);
notifyDataSetChanged();
}
};
class MyViewHolder extends RecyclerView.ViewHolder {
TextView recruiterName, jobName, jobLocation, jobCharge;
ImageView profPic;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
recruiterName = itemView.findViewById(R.id.recruiterName);
jobName = itemView.findViewById(R.id.jobName);
jobLocation = itemView.findViewById(R.id.jobLocation);
jobCharge = itemView.findViewById(R.id.jobCharge);
profPic = itemView.findViewById(R.id.prof_pic);
}
}
jobs.addAll((List)results.values);
[addAll()
将指定集合中的所有元素附加到此列表的末尾,以指定集合的Iterator返回它们的顺序。
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
jobs.clear();
jobs.addAll((List) results.values); // Issue here
notifyDataSetChanged();
}
};
在Java中,可以将特殊的null值分配给对象引用。当应用程序尝试使用NullPointerException时,将引发具有空值的对象引用。
您的(List) results.values
返回null
。在第一次调试(添加断点)时,是否存在values
FilterResults results
。在强制转换为列表之前,请确保results.values
具有数据。
package com.example.oddsynew.Home;
import android.content.Context;
import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import com.example.oddsynew.Modals.Job;
import com.example.oddsynew.R;
import com.squareup.picasso.Picasso;
import java.util.ArrayList;
import java.util.List;
public class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder> implements Filterable {
Context context;
private ArrayList<Job> alListData;
private ArrayList<Job> alListFiltered;
public HomeAdapter(Context c, ArrayList<Job> j) {
context = c;
this.alListData = j;
this.alListFiltered = j;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
return new MyViewHolder(LayoutInflater.from(context).inflate(R.layout.job_row, parent, false));
}
@Override
public void onBindViewHolder(@NonNull final MyViewHolder holder, final int position) {
holder.recruiterName.setText(alListFiltered.get(position).getRecruiter_name());
holder.jobName.setText(alListFiltered.get(position).getJob_name());
holder.jobLocation.setText(alListFiltered.get(position).getLocation());
holder.jobCharge.setText(alListFiltered.get(position).getJob_charge());
Picasso.get().load(alListFiltered.get(position).getProf_pic()).into(holder.profPic);
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
try {
Intent intent = new Intent(context, JobInfo.class);
intent.putExtra("recruiterName", alListFiltered.get(holder.getAdapterPosition()).getRecruiter_name());
intent.putExtra("jobName", alListFiltered.get(holder.getAdapterPosition()).getJob_name());
intent.putExtra("jobCharge", alListFiltered.get(holder.getAdapterPosition()).getJob_charge());
intent.putExtra("jobLocation", alListFiltered.get(holder.getAdapterPosition()).getLocation());
intent.putExtra("profPic", alListFiltered.get(holder.getAdapterPosition()).getProf_pic());
intent.putExtra("startDate", alListFiltered.get(holder.getAdapterPosition()).getStart_date());
intent.putExtra("endDate", alListFiltered.get(holder.getAdapterPosition()).getEnd_date());
intent.putExtra("startTime", alListFiltered.get(holder.getAdapterPosition()).getStart_time());
intent.putExtra("endTime", alListFiltered.get(holder.getAdapterPosition()).getEnd_time());
intent.putExtra("jobDesc", alListFiltered.get(holder.getAdapterPosition()).getJob_desc());
intent.putExtra("jobTasks", alListFiltered.get(holder.getAdapterPosition()).getJob_tasks());
intent.putExtra("addPref", alListFiltered.get(holder.getAdapterPosition()).getAdd_pref());
intent.putExtra("jobID", alListFiltered.get(holder.getAdapterPosition()).getJobID());
context.startActivity(intent);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
@Override
public int getItemCount() {
return alListFiltered.size();
}
@Override
public Filter getFilter() {
return searchFilter;
}
@Override
public Filter getFilter() {
return new Filter() {
@Override
protected FilterResults performFiltering(CharSequence charSequence) {
String charString = charSequence.toString();
if (charString.isEmpty()) {
alListFiltered = alListData;
} else {
List<Job> filteredList = new ArrayList<>();
for (Job row : alListData) {
if (row.getJob_name().toLowerCase().contains(charString.toLowerCase())) {
filteredList.add(row);
}
}
alListFiltered = filteredList;
}
FilterResults filterResults = new FilterResults();
filterResults.values = alListFiltered;
return filterResults;
}
@Override
protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
alListFiltered = (ArrayList<Job>) filterResults.values;
notifyDataSetChanged();
}
};
}
class MyViewHolder extends RecyclerView.ViewHolder {
TextView recruiterName, jobName, jobLocation, jobCharge;
ImageView profPic;
public MyViewHolder(@NonNull View itemView) {
super(itemView);
recruiterName = itemView.findViewById(R.id.recruiterName);
jobName = itemView.findViewById(R.id.jobName);
jobLocation = itemView.findViewById(R.id.jobLocation);
jobCharge = itemView.findViewById(R.id.jobCharge);
profPic = itemView.findViewById(R.id.prof_pic);
}
}
}