我正在使用Recyclerview在MainActivity中显示项目。这可能是被问到但没有找到任何特定的解决方案。我保存项目的方式是通过序列化现在问题是如何在Recycler视图的每个项目上实现删除功能？我在utils.delete中创建了自己的删除功能但是我得到了NPE。
如果我拨打notifyDataSetChanged();，它只会从视图中删除它而不是保存的文件
请帮忙。
ItemAdapter类：
public class Itemadapter extends RecyclerView.Adapter<Itemadapter.itemviewholder> {
static ArrayList<Item> items = new ArrayList<Item>();
Context mcontext;
private String mFilename = utils.EXTRAS_NOTE_FILENAME;
public Itemadapter(MainActivity mainActivity, int item, ArrayList<Item> items)
{
this.items = items;
}
@Override
public itemviewholder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item,parent,false);
itemviewholder itemviewholder = new itemviewholder(view);
return itemviewholder;
}
@Override
public void onBindViewHolder(final itemviewholder holder, final int position) {
Item item = items.get(position);
holder.postnumber.setText(item.getPost_number());
holder.itemname.setText(item.getItem_name());
}
@Override
public int getItemCount() {
return items.size();
}
public class itemviewholder extends RecyclerView.ViewHolder implements View.OnClickListener
{
TextView itemname,postnumber,ico;
private PopupMenu popupMenu;
ImageButton ico1;
public itemviewholder(View view)
{
super(view);
itemname = view.findViewById(R.id.itemdetailsdisplay);
postnumber = view.findViewById(R.id.itemnuberdisplay);
ico1 = view.findViewById(R.id.test);
view.setOnClickListener(this);
ico1.setOnClickListener(this);
}
@Override
public void onClick(final View v) {
final Item mLoadeditem = utils.getitembyfilename(v.getContext(),mFilename);
if (v.getId() == ico1.getId()){
// Toast.makeText(v.getContext(), "ITEM PRESSED = " + String.valueOf(getAdapterPosition()), Toast.LENGTH_SHORT).show();
popupMenu = new PopupMenu(v.getContext(),v);
popupMenu.inflate(R.menu.recycler_item_menu);
popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
@Override
public boolean onMenuItemClick(MenuItem item) {
switch (item.getItemId()){
case R.id.item_delete:
//delete file
utils.delete(v.getContext(),mLoadeditem.getPost_number()+utils.FILE_EXTENSION);
items.remove(getAdapterPosition());
notifyDataSetChanged();
Toast.makeText(v.getContext(),"item deleted",Toast.LENGTH_SHORT).show();
break;
case R.id.item_share:
//share info
Toast.makeText(v.getContext(),"item shared",Toast.LENGTH_SHORT).show();
break;
}
return false;
}
});popupMenu.show();
}
else {
Toast.makeText(v.getContext(), "ROW PRESSED = " + String.valueOf(getAdapterPosition()), Toast.LENGTH_SHORT).show();
}
}
}
}
utils类：
public class utils {
public static final String FILE_EXTENSION = ".bin";
public static final String EXTRAS_NOTE_FILENAME = "EXRAS_NOTES_FILENAME";
public static boolean save(Context context, Item item){
String filename = String.valueOf(item.getPost_number()) +FILE_EXTENSION;
FileOutputStream fos;
ObjectOutputStream oos;
try {
fos= context.openFileOutput(filename,context.MODE_PRIVATE);
oos= new ObjectOutputStream(fos);
oos.writeObject(item);
oos.close();
fos.close();
}catch (Exception e){
e.printStackTrace();
return false;
//something went wrong
}
return true;
}
public static ArrayList<Item> getallsaveditems(Context context){
ArrayList <Item> items= new ArrayList<>();
File filesdir = context.getFilesDir();
ArrayList<String> itemsfiles = new ArrayList<>();
for(String file : filesdir.list()){
if(file.endsWith(FILE_EXTENSION)){
itemsfiles.add(file);
}
}
FileInputStream fis;
ObjectInputStream ois;
for(int i=0; i<itemsfiles.size();i++){
try {
fis = context.openFileInput(itemsfiles.get(i));
ois = new ObjectInputStream(fis);
items.add((Item) ois.readObject());
fis.close();
ois.close();
}catch (IOException | ClassNotFoundException e){
e.printStackTrace();
return null;
}
}
return items;
}
public static Item getitembyfilename(Context context,String filename) {
File file = new File(context.getFilesDir(), filename);
if (file.exists() && !file.isDirectory()) {
Log.v("utils", "file exists" + filename);
FileInputStream fis;
ObjectInputStream ois;
try {
fis = context.openFileInput(filename);
ois = new ObjectInputStream(fis);
Item item = (Item) ois.readObject();
fis.close();
ois.close();
return item;
} catch (IOException |ClassNotFoundException e) {
e.printStackTrace();
return null;
}
}else {
return null;
}
}
public static void delete(Context ctx ,String filename) {
File dir = ctx.getFilesDir();
File file = new File(dir,filename);
if(file.exists()){
file.delete();
}
}
}