I am using a RecyclerView to display information in a Fragment as a list with ImageViews and TextViews. I gave the ImageViews an OnClickListener to get the position and with that the drawable id to display the image in a larger ImageView. This works fine for all the RecyclerView rows which are displayed at the start of the Fragment, but as soon as i click on an ImageView from a row, which i needed to scroll to, i get a NullPointerException with the massage:
java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
The displayed information changes depending on a Spinner in the previews Fragment. The variable is given to the Fragment via the Activity using a fragmentManager.region(d).
The infromationFragment's code is as follwed:
public class Info_Material extends Fragment implements View.OnClickListener {
Button button_back;
Communicator communicator;
static ImageView image_large;
static private RecyclerView recyclerView;
private Information_List_Adapter adapter;
static ArrayList<String> holz_;
static ArrayList<String> land_;
static ArrayList<Integer> blatt_;
static ArrayList<Integer> baum_;
static ArrayList<Integer> frucht_;
String region_;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_info_material, container, false);
holz_ = new ArrayList<>();
land_ = new ArrayList<>();
blatt_ = new ArrayList<>();
baum_ = new ArrayList<>();
frucht_ = new ArrayList<>();
holz_.add(getString(R.string.));
land_.add("");
blatt_.add(R.drawable.);
baum_.add(R.drawable.);
frucht_.add(R.drawable.);
if (region_wahl.equals(getString(a))){
holz_.addAll(Arrays.asList());
land_.addAll(Arrays.asList());
blatt_.addAll(Arrays.asList());
baum_.addAll(Arrays.asList());
frucht_.addAll(Arrays.asList());
}
if (region_wahl.equals(getString(b))){
holz_.addAll(Arrays.asList());
land_.addAll(Arrays.asList());
blatt_.addAll(Arrays.asList());
baum_.addAll(Arrays.asList());
frucht_.addAll(Arrays.asList());
}
recyclerView= (RecyclerView) view.findViewById(R.id.materialInfoList);
adapter = new Information_List_Adapter(getActivity(),getData());
recyclerView.setAdapter(adapter);
recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
button_back = (Button) view.findViewById(R.id.back_I_M);
button_back.setOnClickListener(this);
image_large= (ImageView) view.findViewById(R.id.image_large);
image_large.setOnClickListener(this);
return view;
}
public static List<Information_List> getData() {
List<Information_List> data = new ArrayList<>();
for(int i=0;i<holz_.size() && i<blatt_.size() && i<baum_.size() && i<frucht_.size();i++) {
Information_List current = new Information_List();
current.blattID=blatt_.get(i);
current.baumID=baum_.get(i);
current.fruchtID=frucht_.get(i);
current.holz=holz_.get(i);
data.add(current);
}
return data;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
public void setCommunicator (Communicator communicator) {
this.communicator = communicator;
}
@Override
public void onClick(View view) {
if(view.getId()==R.id.back_I_M){
String d;
d = "back";
communicator.finish_I_M(d);
}
if(view.getId()==R.id.image_large){
image_large.setImageDrawable(null);
}
}
public void region (String d) {
region_ = d;
}
static void enlarge (int position,String data){
ImageView imageView=null;
if(data.equals("blatt")){
imageView = (ImageView)recyclerView.getChildAt(position).findViewById(R.id.info_list_blatt);
}
if(data.equals("baum")){
imageView = (ImageView)recyclerView.getChildAt(position).findViewById(R.id.info_list_baum);
}
if(data.equals("frucht")){
imageView = (ImageView)recyclerView.getChildAt(position).findViewById(R.id.info_list_frucht);
}
BitmapDrawable drawable = (BitmapDrawable) imageView.getDrawable();
image_large.setImageDrawable(drawable);
}
public interface Communicator {
void finish_I_M (String data);
}
}
The AdapterClass:
public class Information_List_Adapter extends RecyclerView.Adapter <Information_List_Adapter.MyViewHolder> {
private Context context;
private LayoutInflater inflater;
List<Information_List> data = Collections.emptyList();
public Information_List_Adapter(Context context, List<Information_List> data) {
this.context=context;
inflater= LayoutInflater.from(context);
this.data=data;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate (R.layout.custom_info_material_row,parent,false);
MyViewHolder holder = new MyViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
holder.holz.setText(Info_Material.holz_.get(position));
holder.land.setText(Info_Material.land_.get(position));
holder.blattID.setImageResource(Info_Material.blatt_.get(position));
holder.baumID.setImageResource(Info_Material.baum_.get(position));
holder.fruchtID.setImageResource(Info_Material.frucht_.get(position));
}
@Override
public int getItemCount() {
return Info_Material.holz_.size();
}
class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
TextView holz;
TextView land;
ImageView blattID;
ImageView baumID;
ImageView fruchtID;
public MyViewHolder(View itemView) {
super(itemView);
holz= (TextView) itemView.findViewById(R.id.info_list_holz);
land = (TextView) itemView.findViewById(R.id.info_list_land);
blattID = (ImageView) itemView.findViewById(R.id.info_list_blatt);
baumID = (ImageView) itemView.findViewById(R.id.info_list_baum);
fruchtID = (ImageView) itemView.findViewById(R.id.info_list_frucht);
blattID.setOnClickListener(this);
baumID.setOnClickListener(this);
fruchtID.setOnClickListener(this);
}
@Override
public void onClick(View v) {
if(v.getId()==R.id.info_list_blatt){
Info_Material.enlarge(getAdapterPosition(),"blatt");
}
if(v.getId()==R.id.info_list_baum){
Info_Material.enlarge(getAdapterPosition(),"baum");
}
if(v.getId()==R.id.info_list_frucht){
Info_Material.enlarge(getAdapterPosition(),"frucht");
}
}
}
}
As stated above, this method works fine for all initially created rows when starting the Fragment, but as soon, as a newly created row (not initially shown on the screen) is clicked the app crashes with said NullPointerException.
Since i am still pretty new to Java programming i don't really have an idea where i could start looking for the mistake, so i would appreciate any hint on where the error might occur.
Thanks in advance.