"Non-static method 'getActivity()' cannot be referenced from a static context" in recyclerview adapter

Question

I made custom gallery using fragment and recyclerview. I want to make multiple selection within it, to appear Actionbar with menu when I select pictures. So I made ActionMode in my adapter and tried to start action mode when the image were long clicked. But I can't bring the activity of my gallery fragment... with the error "Non-static method 'getActivity()' cannot be referenced from a static context".

Furthermore, I selected only one image but other images are selected together. How can I fix it?

public class exAdap extends RecyclerView.Adapter<exAdap.ViewHolder>


ActionMode.Callback mActionCallback = new ActionMode.Callback(){
    @Override
    public boolean onPrepareActionMode(ActionMode mode, Menu menu){
        return false;
    }

    @Override
    public void onDestroyActionMode(ActionMode mode){
        mActionMode = null;
    }

    @Override
    public boolean onCreateActionMode(ActionMode mode, Menu menu){
        MenuInflater inflater = mode.getMenuInflater();
        inflater.inflate(R.menu.pic_menu, menu);
        return true;
    }

    @Override
    public boolean onActionItemClicked(ActionMode mode, MenuItem item) {
        switch(item.getItemId()){
            case R.id.menu_email:
                mode.finish();
                break;
        }
        return false;
    }
};

public exAdap(ArrayList<String> datas, Context context) {
    this.datas = datas;
    this.context = context;
}

@NonNull
@Override
public exAdap.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, 
  int viewType) {
    View view;
    LayoutInflater layoutInflater = LayoutInflater.from(context);
    view = layoutInflater.inflate(R.layout.activity_gallery, parent, 
false);

    return new ViewHolder(view);
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
    
 Glide.with(context).load(datas.get(position)).into(holder.getImage());
    String currentImage = datas.get(position);

    holder.image.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(multiSelect){
                selected.add(currentImage);
                holder.check.setVisibility(View.VISIBLE);
                holder.check.setChecked(true);
            }
        }
    });

    holder.image.setOnLongClickListener(new View.OnLongClickListener() {
        @Override
        public boolean onLongClick(View view) {
            if (!multiSelect) {
                multiSelect=true;
                mActionMode = ((AppCompatActivity) 
 
 
fragment_gallery.getActivity()).startSupportActionMode(mActionCallback);
                if(selected.contains(currentImage)){
                    selected.remove(currentImage);
                }
                else{
                    selected.add(currentImage);
                    holder.check.setVisibility(View.VISIBLE);
                    holder.check.setChecked(true);
                }
            }
            return true;
        }
    });

}

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

public void addAll(ArrayList<String> datas) {
    clearAll(false);
    this.datas = datas;
    notifyDataSetChanged();
}

public void clearAll(boolean isNotify) {
    datas.clear();
    selected.clear();
    if (isNotify) notifyDataSetChanged();
}

public void clearSelected() {
    selected.clear();
    notifyDataSetChanged();
}

public void selectAll() {
    selected.clear();
    selected.addAll(datas);
    notifyDataSetChanged();
}

public ArrayList<String> getSelected() {
    return selected;
}


public class ViewHolder extends RecyclerView.ViewHolder {

    ImageView image;
    CheckBox check;

    public ViewHolder(View itemView) {
        super(itemView);
        image = itemView.findViewById((R.id.recyclerview_row_image));
        check = itemView.findViewById(R.id.checkImage);

    }

    public ImageView getImage() {
        return this.image;
    }


}

'''

public class fragment_gallery extends Fragment


private ListView m_list;
private ArrayList<String> listt;

private RecyclerView recyclerView;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View view =  inflater.inflate(R.layout.fragment_gallery, container, false);
    //listt = getPic();
    recyclerView = view.findViewById(R.id.recyclerView);
    recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 3));
    recyclerView.setAdapter(new exAdap(getPic(), getContext()));
    return view;
}

public ArrayList<String> getPic() {
    ArrayList<String> fileList = new ArrayList<>();
    Uri uri = MediaStore.Images.Media.EXTERNAL_CONTENT_URI;
    String[] projection = {MediaStore.MediaColumns.DATA, MediaStore.MediaColumns.DISPLAY_NAME};

    Cursor cursor = getActivity().getContentResolver().query(uri, projection, null, null, MediaStore.MediaColumns.DATE_ADDED + " desc");
    int columnIndex = cursor.getColumnIndexOrThrow(MediaStore.MediaColumns.DATA);
    int columnDisplayname = cursor.getColumnIndexOrThrow(MediaStore.MediaColumns.DISPLAY_NAME);
    int lastIndex;
    while (cursor.moveToNext()) {
        String absolutePathOfImage = cursor.getString(columnIndex);
        String nameOfFile = cursor.getString(columnDisplayname);
        lastIndex = absolutePathOfImage.lastIndexOf(nameOfFile);
        lastIndex = lastIndex >= 0 ? lastIndex : nameOfFile.length() - 1;

        if (!TextUtils.isEmpty(absolutePathOfImage)) {
            fileList.add(absolutePathOfImage);
        }
    }
    cursor.close();
    return fileList;
}

'''