I have trouble searching my data from the remote server to my RecyclerView. It is showing the above-mentioned error, and the app crashes as soon as I Search from the list. I have highlighted the functions where the error occurs in log cat. I also mentioned where is the function in my classes.
Adapter Classs:-
public class Question_Adapter extends RecyclerView.Adapter<Question_Adapter.QuestionViewHolder> implements Filterable {
private List<Question_Model> question_modelList = new ArrayList<Question_Model>();
private List<Question_Model> question_models_another_list;
Context context;
public Question_Adapter(List<Question_Model> question_modelList){
this.question_modelList = question_modelList;
question_models_another_list = new ArrayList<>(question_modelList);
}
class QuestionViewHolder extends RecyclerView.ViewHolder {
TextView semester, course_name, course_teacher, session_year;
ImageView readPDF, downPDF;
CardView card;
public QuestionViewHolder(@NonNull View itemView) {
super(itemView);
semester = itemView.findViewById(R.id.semester);
course_name = itemView.findViewById(R.id.course_name);
course_teacher = itemView.findViewById(R.id.course_teacher);
session_year = itemView.findViewById(R.id.session_year);
card = itemView.findViewById(R.id.card);
readPDF = itemView.findViewById(R.id.readPDF);
downPDF = itemView.findViewById(R.id.downPDF);
}
}
@NonNull
@Override
public Question_Adapter.QuestionViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.pdf_view_design,parent,false);
context = parent.getContext();
return new QuestionViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull Question_Adapter.QuestionViewHolder holder, int position) {
Question_Model current_book = question_modelList.get(position);
holder.semester.setText(current_book.getSemester());
holder.course_name.setText(current_book.getCourse_name());
holder.course_teacher.setText(current_book.getCourse_teacher());
holder.session_year.setText(current_book.getExam_type()+" - "+current_book.getSession_name());
holder.readPDF.setOnClickListener(v -> readPDFInformation(current_book.getPdf_link()));
String file_name = current_book.getYear()+"_"+current_book.getSemester()+"_"+current_book.getCourse_name()+"_"+current_book.getCourse_teacher();
holder.downPDF.setOnClickListener(v -> downPDFInformation(current_book.getPdf_link(),file_name));
}
public void sortNameByAsc() {
Comparator<Question_Model> comparator = new Comparator<Question_Model>() {
@Override
public int compare(Question_Model object1, Question_Model object2) {
return object1.getSemester().compareToIgnoreCase(object2.getSemester());
}
};
Collections.sort(question_modelList, comparator);
notifyDataSetChanged();
}
public void sortFilterByAsc() {
Comparator<Question_Model> comparator = new Comparator<Question_Model>() {
@Override
public int compare(Question_Model object1, Question_Model object2) {
return object1.getSemester().compareToIgnoreCase(object2.getSemester());
}
};
Collections.sort(question_models_another_list, comparator);
notifyDataSetChanged();
}
private long downPDFInformation(String url, String fileName) {
DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url + ""));
request.setTitle(fileName);
request.setMimeType("application/pdf");
request.allowScanningByMediaScanner();
request.setAllowedOverMetered(true);
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "PUC/" + fileName+".pdf");
DownloadManager downloadManager = (DownloadManager) context.getSystemService(DOWNLOAD_SERVICE);
return downloadManager.enqueue(request);
}
private void readPDFInformation(String url) {
try {
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(Uri.parse(url), "application/pdf");
intent.setFlags(Intent.FLAG_ACTIVITY_NO_HISTORY);
context.startActivity(intent);
} catch (Exception e) {
//error
}
}
@Override
public int getItemCount() {
return question_modelList.size();
}
@Override
public Filter getFilter() {
return filter;
}
public Filter filter= new Filter() {
@Override
public FilterResults performFiltering(CharSequence constraint) {
List<Question_Model> filterlist=new ArrayList<>();
if(constraint==null|| constraint.length()==0){
filterlist.addAll(question_models_another_list);
}
else{
String pattrn=constraint.toString().toLowerCase().trim();
for(Question_Model item :question_models_another_list){
if(item.getCourse_name().toLowerCase().contains(pattrn) ||
item.getCourse_teacher().toLowerCase().contains(pattrn)||
item.getYear().toLowerCase().contains(pattrn)||
item.getSemester().toLowerCase().contains(pattrn)||
item.getExam_type().toLowerCase().contains(pattrn)||
item.getPdf_file_name().toLowerCase().contains(pattrn)){
filterlist.add(item);
}
}
}
FilterResults filterResults=new FilterResults();
filterResults.values=filterlist;
return filterResults;
}
@Override
protected void publishResults(CharSequence constraint, FilterResults results) {
question_modelList.clear();
question_modelList.addAll((List)results.values);
notifyDataSetChanged();
}
};
}
Model Class:-
public class Question_Model {
private String exam_type, semester, year, session_name, course_teacher, course_name, pdf_link, pdf_file_name, upload_time, key;
public Question_Model(String exam_type, String semester, String year, String session_name, String course_teacher, String course_name, String pdf_link, String upload_time, String pdf_file_name, String key) {
this.exam_type = exam_type;
this.semester = semester;
this.year = year;
this.session_name = session_name;
this.course_teacher = course_teacher;
this.course_name = course_name;
this.pdf_link = pdf_link;
this.upload_time = upload_time;
this.pdf_file_name = pdf_file_name;
this.key = key;
}
public String getExam_type() {
return exam_type;
}
public void setExam_type(String exam_type) {
this.exam_type = exam_type;
}
public String getSession_name() {
return session_name;
}
public void setSession_name(String session_name) {
this.session_name = session_name;
}
public String getPdf_file_name() {
return pdf_file_name;
}
public void setPdf_file_name(String pdf_file_name) {
this.pdf_file_name = pdf_file_name;
}
public String getSemester() {
return semester;
}
public void setSemester(String semester) {
this.semester = semester;
}
public String getYear() {
return year;
}
public void setYear(String year) {
this.year = year;
}
public String getCourse_teacher() {
return course_teacher;
}
public void setCourse_teacher(String course_teacher) {
this.course_teacher = course_teacher;
}
public String getCourse_name() {
return course_name;
}
public void setCourse_name(String course_name) {
this.course_name = course_name;
}
public String getPdf_link() {
return pdf_link;
}
public void setPdf_link(String pdf_link) {
this.pdf_link = pdf_link;
}
public String getUpload_time() {
return upload_time;
}
public void setUpload_time(String upload_time) {
this.upload_time = upload_time;
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
}
Logcat
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.tanzim.pucquestionbot, PID: 16358
java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.Object[] java.util.Collection.toArray()' on a null object reference
at java.util.ArrayList.addAll(ArrayList.java:588)
at com.tanzim.pucquestionbot.home.Question_Adapter$3.publishResults(Question_Adapter.java:176)
at android.widget.Filter$ResultsHandler.handleMessage(Filter.java:284)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:246)
at android.app.ActivityThread.main(ActivityThread.java:8653)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:602)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1130)
***NB: Searching performing from androidx.appcompat.widget.SearchView ***
