Java 循环查看滚动并保持在旧位置不要进入顶部

我的问题是当我在循环视图中滚动我的数据以便加载新数据时，但问题是当新数据从第一个产品开始加载我的循环视图时，

我需要保持旧位置，只滚动新数据，而不是所有新旧数据

目前我正在添加我的文件ADeptor文件和主文件的完整代码

public class adepter extends RecyclerView.Adapter<adepter.viewholder> {

    private Context mCtx;
    private List<Product> productList;
        public adepter(Context mCtx, List<Product> productList) {
            this.mCtx = mCtx;
            this.productList = productList;
        }

    @NonNull
    @Override
    public adepter.viewholder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater=LayoutInflater.from(mCtx);
        View v =inflater.inflate(R.layout.product_list, parent, false);
        final viewholder vh = new viewholder(v);
        vh.itemView.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Product product = productList.get(vh.getAdapterPosition());
                //do the page opening here
                Intent intent = new Intent(mCtx, product_info.class);
                intent.putExtra("id",product.getId());

                mCtx.startActivity(intent);

            }
        });
        return vh;

    }

    @Override
    public void onBindViewHolder(@NonNull adepter.viewholder holder, int position) {
        Product product = productList.get(position);
        //loading the image
        Glide.with(mCtx)
                .load(product.getImage())
                .into(holder.imageView);
        holder.textViewTitle.setText(product.getTitle());
        holder.textViewShortDesc.setText(product.getShortdesc());
        holder.textViewtype.setText(String.valueOf(product.getType()));
        holder.textViewPrice.setText("Rs: "+String.valueOf(product.getPrice()));
    }

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





    public class viewholder extends RecyclerView.ViewHolder{
        TextView textViewTitle, textViewShortDesc, textViewtype, textViewPrice;
        ImageView imageView;
        public viewholder(@NonNull View itemView) {
            super(itemView);
            textViewTitle = itemView.findViewById(R.id.textViewTitle);
            textViewShortDesc = itemView.findViewById(R.id.textViewShortDesc);
            textViewtype = itemView.findViewById(R.id.textViewRating);
            textViewPrice = itemView.findViewById(R.id.textViewPrice);
            imageView = itemView.findViewById(R.id.imageView);
        }
    }
}

公共类adepter扩展了RecyclerView.Adapter{
私有上下文mCtx；
私有列表产品列表；
公共adepter（上下文mCtx，列表productList）{
this.mCtx=mCtx；
this.productList=productList；
}
@非空
@凌驾
public adepter.viewholder onCreateViewHolder（@NonNull ViewGroup父级，int viewType）{
LayoutFlater充气机=LayoutFlater.from（mCtx）；
视图v=充气机。充气（R.layout.product_list，父项，false）；
最终视窗夹持器vh=新视窗夹持器（v）；
vh.itemView.setOnClickListener（新视图.OnClickListener（）{
公共void onClick（视图v）{
Product=productList.get（vh.getAdapterPosition（））；
//这页在这儿打开吗
意向意向=新意向（mCtx，产品信息类）；
intent.putExtra（“id”，product.getId（））；
mCtx.启动触觉（意图）；
}
});
返回vh；
}
@凌驾
BindViewHolder上的公共无效（@NonNull adepter.viewholder，int位置）{
产品=产品列表。获取（位置）；
//加载图像
滑翔带（mCtx）
.load（product.getImage（））
.插入（支架.图像视图）；
holder.textViewTitle.setText（product.getTitle（））；
holder.textViewShortDesc.setText（product.getShortdesc（））；
holder.textViewtype.setText（String.valueOf（product.getType（））；
holder.textViewPrice.setText（“Rs:+String.valueOf（product.getPrice（）））；
}
@凌驾
public int getItemCount（）{
返回productList.size（）；
}
公共类viewholder扩展了RecyclerView.viewholder{
TextView textViewTitle、textViewShortDesc、textViewtype、textViewPrice；
图像视图图像视图；
公共视图持有者（@NonNull View itemView）{
超级（项目视图）；
textViewTitle=itemView.findViewById（R.id.textViewTitle）；
textViewShortDesc=itemView.findViewById（R.id.textViewShortDesc）；
textViewtype=itemView.findViewById（R.id.textViewRating）；
textViewPrice=itemView.findViewById（R.id.textViewPrice）；
imageView=itemView.findViewById（R.id.imageView）；
}
}
}

公共类主页扩展应用程序活动{
//存储所有产品的列表
列出产品清单；
//回收视图
回收视图回收视图；
ProgressBar-Pbar；
网格布局经理；
int-token=1；
布尔isScrolling=false；
int currentItems、totalItems、scrollOutItems；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_home）；
Pbar=findViewById（R.id.progressBar1）；
//从xml获取recyclerview
recyclerView=findViewById（R.id.recylcerView）；
recyclerView.setHasFixedSize（true）；
manager=新的GridLayoutManager（这是2）；
recyclerView.setLayoutManager（管理器）；
//初始化产品列表
productList=新的ArrayList（）；
recyclerView.addOnScrollListener（新的recyclerView.OnScrollListener（）{
@凌驾
CrollStateChanged上的公共无效（RecyclerView RecyclerView，int newState）{
super.onScrollStateChanged（recyclerView、newState）；
if（newState==AbsListView.OnScrollListener.SCROLL\u STATE\u TOUCH\u SCROLL）
{
isScrolling=true；
}
}
@凌驾
已填空的公共空间（RecyclerView RecyclerView、int dx、int dy）{
super.onScrolled（recyclerView、dx、dy）；
currentItems=manager.getChildCount（）；
totalItems=manager.getItemCount（）；
scrollOutItems=manager.findFirstVisibleItemPosition（）；
if（isScrolling&&（currentItems+scrollOutItems==totalItems））
{
IsCrolling=假；
令牌++；
getData（）；
}
}
});
getData（）；
}
私有void getData（）{
字符串url=”https://shop.com/index.php";
url=url+“&pg=“+String.valueOf（令牌）；
Pbar.setVisibility（View.VISIBLE）；
StringRequest StringRequest=新的StringRequest（Request.Method.GET，url，
新的Response.Listener（）{
@凌驾
公共void onResponse（字符串响应）{
//Toast.makeText（getApplicationContext（），“volly ok”，Toast.LENGTH\u LONG.show（）；
试一试{
//将字符串转换为json数组对象
JSONArray数组=新的JSONArray（响应）；
//遍历所有对象
对于（int i=0；i
public class home extends AppCompatActivity {

  //a list to store all the products
    List<Product> productList;
    //the recyclerview
    RecyclerView recyclerView;
    ProgressBar Pbar;
    GridLayoutManager manager;
    int token = 1;
  Boolean isScrolling = false;
    int currentItems, totalItems, scrollOutItems;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        Pbar = findViewById(R.id.progressBar1);
        //getting the recyclerview from xml
        recyclerView = findViewById(R.id.recylcerView);
        recyclerView.setHasFixedSize(true);
         manager = new GridLayoutManager(this, 2);
        recyclerView.setLayoutManager(manager);

        //initializing the productlist
        productList = new ArrayList<>();





        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                if(newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL)
                {
                    isScrolling = true;
                }
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                currentItems = manager.getChildCount();
                totalItems = manager.getItemCount();
                scrollOutItems = manager.findFirstVisibleItemPosition();

                if(isScrolling && (currentItems + scrollOutItems == totalItems))
                {
                    isScrolling = false;
                    token++;
                    getData();
                }
            }
        });
        getData();


    }





    private void   getData(){
         String url = "https://shop.com/index.php";

         url = url+ "&pg="+ String.valueOf(token);

        Pbar.setVisibility(View.VISIBLE);

        StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        //   Toast.makeText(getApplicationContext(),"volly ok ",Toast.LENGTH_LONG).show();
                        try {
                            //converting the string to json array object
                            JSONArray array = new JSONArray(response);
                            //traversing through all the object
                            for (int i = 0; i < array.length(); i++) {
                                //getting product object from json array
                                JSONObject product = array.getJSONObject(i);
                                //adding the product to product list
                                productList.add(new Product(
                                        product.getInt("id"),
                                        product.getString("title"),
                                        product.getString("shortdesc"),
                                        product.getString("type"),
                                        product.getString("price"),
                                        product.getString("image")
                                ));
                            }
                            //  Toast.makeText(getApplicationContext(),productList+ "volly ok ",Toast.LENGTH_LONG).show();

                          adepter a = new adepter(home.this, productList);
                            recyclerView.setAdapter(a);

                            Pbar.setVisibility(View.GONE);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Toast.makeText(getApplicationContext(), "Server Error" ,Toast.LENGTH_LONG).show();
                    }
                });

        //adding our stringrequest to queue
        Volley.newRequestQueue(this).add(stringRequest);
    }

}

public class home extends AppCompatActivity {

  //a list to store all the products
    List<Product> productList;
    //the recyclerview
    RecyclerView recyclerView;
    adepter a;
    ProgressBar Pbar;
    GridLayoutManager manager;
    int token = 1;
  Boolean isScrolling = false;
    int currentItems, totalItems, scrollOutItems;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home);

        Pbar = findViewById(R.id.progressBar1);
        //getting the recyclerview from xml
        recyclerView = findViewById(R.id.recylcerView);
        recyclerView.setHasFixedSize(true);
         manager = new GridLayoutManager(this, 2);
        recyclerView.setLayoutManager(manager);

        //initializing the productlist
        productList = new ArrayList<>();


 a = new adepter(home.this, productList);
                recyclerView.setAdapter(a);


        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                if(newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL)
                {
                    isScrolling = true;
                }
            }

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                currentItems = manager.getChildCount();
                totalItems = manager.getItemCount();
                scrollOutItems = manager.findFirstVisibleItemPosition();

                if(isScrolling && (currentItems + scrollOutItems == totalItems))
                {
                    isScrolling = false;
                    token++;
                    getData();
                }
            }
        });
        getData();


    }





    private void   getData(){
         String url = "https://shop.com/index.php";

         url = url+ "&pg="+ String.valueOf(token);

        Pbar.setVisibility(View.VISIBLE);

        StringRequest stringRequest = new StringRequest(Request.Method.GET, url,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        //   Toast.makeText(getApplicationContext(),"volly ok ",Toast.LENGTH_LONG).show();
                        try {
                            //converting the string to json array object
                            JSONArray array = new JSONArray(response);
                            //traversing through all the object
                            for (int i = 0; i < array.length(); i++) {
                                //getting product object from json array
                                JSONObject product = array.getJSONObject(i);
                                //adding the product to product list
                                productList.add(new Product(
                                        product.getInt("id"),
                                        product.getString("title"),
                                        product.getString("shortdesc"),
                                        product.getString("type"),
                                        product.getString("price"),
                                        product.getString("image")
                                ));
                            }
                            a.notifyDataSetChanged();



                            Pbar.setVisibility(View.GONE);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Toast.makeText(getApplicationContext(), "Server Error" ,Toast.LENGTH_LONG).show();
                    }
                });

        //adding our stringrequest to queue
        Volley.newRequestQueue(this).add(stringRequest);
    }

}