如何在Android Studio中避免ArrayList中的重复项目

Question

我正在尝试开发一个杂货配送应用程序。用户选择一家商店，然后将一些产品添加到购物车中，然后下订单。然而，我遇到了一个问题，当用户将相同的产品添加到购物车时，产品就会重复。例如，如果用户添加数量为5的肥皂，然后再次添加数量为10的相同肥皂，则推车中的产品是重复的，即5和10的单独数量。我想要的是，如果用户添加了相同的产品，那么只有数量应该改变，而不是重复整个项目。此外，当下订单时，订单中只下了数量10，但价格是15(即5+10(。我相信这是因为两种情况下的产品id都是相同的，因此它们在购物车中是重复的，这就是为什么我希望当用户将相同的产品添加到购物车时，只有数量应该改变。这是我的代码，我从这个问题中删除了很多代码，使其尽可能简单，完整的代码太长了。

注意：请查看addToCart按钮，我认为问题就在那里

AdapterProductUser.java

public class AdapterProductUser extends RecyclerView.Adapter<AdapterProductUser.HolderProductUser> implements Filterable {
private Context context;
public ArrayList<ModelProduct> productsist, filterList;
private FilterProductUser filter;
public AdapterProductUser(Context context, ArrayList<ModelProduct> productsist) {
this.context = context;
this.productsist = productsist;
this.filterList = productsist;
}

@NonNull
@Override
public HolderProductUser onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
/*inflate layout*/
View view = LayoutInflater.from(context).inflate(R.layout.row_product_user,parent,false);
return new HolderProductUser(view);
}



@Override
public void onBindViewHolder(@NonNull HolderProductUser holder, int position) {
/*get data*/
final ModelProduct modelProduct = productsist.get(position);
String discountAvailable = modelProduct.getDiscountAvailable();
String discountNote = modelProduct.getDiscountNote();
String discountPrice = modelProduct.getDiscountPrice();
String productCategory = modelProduct.getProductCategory();
String originalPrice = modelProduct.getOriginalPrice();
String productDescription = modelProduct.getProductDescription();
String productTitle = modelProduct.getProductTitle();
String productQuantity = modelProduct.getProductQuantity();
String productId = modelProduct.getProductId();
String timestamp = modelProduct.getTimestamp();
String productIcon = modelProduct.getProductIcon();
/*set data*/
holder.titleTv.setText(productTitle);
holder.discountedNoteTv.setText(discountNote);
holder.descriptionTv.setText(productDescription);
holder.originalPriceTv.setText("Rs "+originalPrice);
holder.discountedPriceTv.setText("Rs "+discountPrice);

}

// Some more code here

addToCart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (quantityEt.getText().toString().trim().equals("0") || quantityEt.getText().toString().trim().isEmpty()){
quantityEt.setError("Please enter a quantity");
return;
}
String title = titleTv.getText().toString().trim();
String priceEach = price;
String totalPrice = finalPriceTv.getText().toString().trim().replace("Rs ","");
//                Double d = Double.parseDouble(quantityEt.getText().toString().trim());
//                int integer = d.intValue();
String quantity = quantityEt.getText().toString().trim();
//String quantity = Integer.toString(integer);

/*add to db (SQLite)*/
addToCart(productId, title, priceEach, totalPrice, quantity);
dialog.dismiss();
}
});
}
private int itemId = 1;
private void addToCart(String productId, String title, String priceEach, String price, String quantity) {
itemId++;
EasyDB easyDB = EasyDB.init(context,"ITEMS_DB")
.setTableName("ITEMS_TABLE")
.addColumn(new Column("Item_Id", new String[]{"text","unique"}))
.addColumn(new Column("Item_PID", new String[]{"text","not null"}))
.addColumn(new Column("Item_Name", new String[]{"text","not null"}))
.addColumn(new Column("Item_Price_Each", new String[]{"text","not null"}))
.addColumn(new Column("Item_Price", new String[]{"text","not null"}))
.addColumn(new Column("Item_Quantity", new String[]{"text","not null"}))
.doneTableColumn();


Boolean b = easyDB.addData("Item_Id",itemId)
.addData("Item_PID",productId)
.addData("Item_Name",title)
.addData("Item_Price_Each",priceEach)
.addData("Item_Price",price)
.addData("Item_Quantity",quantity)
.doneDataAdding();

Toast.makeText(context, "Added to cart...", Toast.LENGTH_SHORT).show();
/*update cart count*/
((ShopDetailsActivity)context).cartCount();

}
@Override
public int getItemCount() {
return productsist.size();
}
@Override
public Filter getFilter() {
if (filter == null){
filter = new FilterProductUser(this,filterList);
}
return filter;
}
class HolderProductUser extends RecyclerView.ViewHolder{
/*ui views*/
private ImageView productIconIv, nextIv;
private TextView discountedNoteTv, titleTv, descriptionTv, addToCartTv,
discountedPriceTv, originalPriceTv;

public HolderProductUser(@NonNull View itemView) {
super(itemView);
productIconIv = itemView.findViewById(R.id.productIconIv);
nextIv = itemView.findViewById(R.id.nextIv);
discountedNoteTv = itemView.findViewById(R.id.discountedNoteTv);
titleTv = itemView.findViewById(R.id.titleTv);
addToCartTv = itemView.findViewById(R.id.addToCartTv);
descriptionTv = itemView.findViewById(R.id.descriptionTv);
discountedPriceTv = itemView.findViewById(R.id.discountedPriceTv);
originalPriceTv = itemView.findViewById(R.id.originalPriceTv);
}
}
}

ShopDetailsActivity.java 注意：这里请查看cartCount和submitOrder方法，我认为问题就在那里

public class ShopDetailsActivity extends AppCompatActivity {
/*Declare UI Views*/
private ArrayList<ModelProduct> productsList;
private AdapterProductUser adapterProductUser;
/*cart*/
public ArrayList<ModelCartItem> cartItemList;
private AdapterCartItem adapterCartItem;
AlertDialog dialog;
private EasyDB easyDB;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getWindow().requestFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_shop_details);
// UI initialization here

loadMyInfo();
loadShopDetails();
loadShopProducts();
loadReviews(); /*avg rating, set on ratingbar*/
/*declare it in class level and init in onCreate*/
easyDB = EasyDB.init(this,"ITEMS_DB")
.setTableName("ITEMS_TABLE")
.addColumn(new Column("Item_Id", new String[]{"text","unique"}))
.addColumn(new Column("Item_PID", new String[]{"text","not null"}))
.addColumn(new Column("Item_Name", new String[]{"text","not null"}))
.addColumn(new Column("Item_Price_Each", new String[]{"text","not null"}))
.addColumn(new Column("Item_Price", new String[]{"text","not null"}))
.addColumn(new Column("Item_Quantity", new String[]{"text","not null"}))
.doneTableColumn();
/*each shop have its own products and orders so if the user add items to cart and go back and open cart in different shop then cart should be different*/
/*so delete cart data whenever user open this activity*/
deleteCartData();
cartCount();

cartBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
/*show cart dialog*/
showCartDialog();
}
});

public void cartCount(){
/*keep this method public so we can access it in adapter*/
/*get cart coont*/
int count = easyDB.getAllData().getCount();
if (count <= 0 ){
/*cart is empty*/
cartCountTv.setVisibility(View.GONE);
}
else {
/*have some item in cart, show cartCountTv and set count*/
cartCountTv.setVisibility(View.VISIBLE);
cartCountTv.setText(""+count); /*concatenate with string, because we can set integer in textview*/
}
}

// Some more code here
/*dialog*/
AlertDialog.Builder builder = new AlertDialog.Builder(this);
/*set view to dialog*/
builder.setView(view);
shopNameTv.setText(shopName);
EasyDB easyDB = EasyDB.init(this,"ITEMS_DB")
.setTableName("ITEMS_TABLE")
.addColumn(new Column("Item_Id", new String[]{"text","unique"}))
.addColumn(new Column("Item_PID", new String[]{"text","not null"}))
.addColumn(new Column("Item_Name", new String[]{"text","not null"}))
.addColumn(new Column("Item_Price_Each", new String[]{"text","not null"}))
.addColumn(new Column("Item_Price", new String[]{"text","not null"}))
.addColumn(new Column("Item_Quantity", new String[]{"text","not null"}))
.doneTableColumn();
/*get all records from db*/
Cursor res = easyDB.getAllData();
while (res.moveToNext()){
String id = res.getString(1);
String pId = res.getString(2);
String name = res.getString(3);
String price = res.getString(4);
String cost = res.getString(5);
String quantity = res.getString(6);
allTotalPrice = allTotalPrice + Double.parseDouble(cost);
ModelCartItem modelCartItem = new ModelCartItem(
""+id,
""+pId,
""+name,
""+price,
""+cost,
""+quantity
);
cartItemList.add(modelCartItem);

}

/*place order*/
checkoutBtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
/*first validate delivery address*/
if (myLatitude.equals("") || myLatitude.equals("null") || myLongitude.equals("") || myLongitude.equals("null")){
/*user did not enter address in profile*/
Toast.makeText(ShopDetailsActivity.this, "Error: Please enter your address in your profile before placing order...", Toast.LENGTH_LONG).show();
return; /*don't proceed further*/
}
if (myPhone.equals("") || myPhone.equals("null")){
/*user did not enter phone in profile*/
Toast.makeText(ShopDetailsActivity.this, "Error: Please enter your phone number in your profile before placing order...", Toast.LENGTH_LONG).show();
return; /*don't proceed further*/
}
if (cartItemList.size() == 0){
/*cart list is empty*/
Toast.makeText(ShopDetailsActivity.this, "Error: Your cart is empty", Toast.LENGTH_LONG).show();
return;
}
submitOrder();
}
});

}

private void submitOrder() {
/*show progress dialog*/
progressDialog.setMessage("Placing order...");
progressDialog.show();
/*for order id and order time*/
final String timestamp = ""+System.currentTimeMillis();
String cost = allTotalPriceTv.getText().toString().trim().replace("Rs ",""); /*remove Rs if contains*/
/*add latitude, longitude of user to each order | delete previous orders from firebase or add manually to them*/
/*setup order data*/
HashMap<String,String> hashMap = new HashMap<>();
hashMap.put("orderId",""+timestamp);
hashMap.put("orderTime",""+timestamp);
hashMap.put("orderStatus","In Progress"); /*In Progress/Completed/Cancelled*/
hashMap.put("orderCost",""+cost);
hashMap.put("orderBy",""+firebaseAuth.getUid());
hashMap.put("orderTo",""+shopUid);
hashMap.put("deliveryFee",""+deliveryFee);
hashMap.put("latitude",""+myLatitude);
hashMap.put("longitude",""+myLongitude);
if (isPromoCodeApplied){
hashMap.put("discount",""+promoPrice);
}
else {
hashMap.put("discount","0");
}
/*add to db*/
final DatabaseReference ref = FirebaseDatabase.getInstance().getReference("Users").child(shopUid).child("Orders");
ref.child(timestamp).setValue(hashMap)
.addOnSuccessListener(new OnSuccessListener<Void>() {
@Override
public void onSuccess(Void aVoid) {
/*order info added now add order items*/
for (int i=0; i<cartItemList.size(); i++){
String pId = cartItemList.get(i).getpId();
String id = cartItemList.get(i).getId();
String cost = cartItemList.get(i).getCost();
String name = cartItemList.get(i).getName();
String price = cartItemList.get(i).getPrice();
String quantity = cartItemList.get(i).getQuantity();
HashMap<String,String> hashMap1 = new HashMap<>();
hashMap1.put("pId",pId);
hashMap1.put("name",name);
hashMap1.put("cost",cost);
hashMap1.put("price",price);
hashMap1.put("quantity",quantity);
int countA= Collections.frequency(cartItemList, pId);
Toast.makeText(ShopDetailsActivity.this, ""+countA, Toast.LENGTH_SHORT).show();
ref.child(timestamp).child("Items").child(pId).setValue(hashMap1);
}
progressDialog.dismiss();
deleteCartData();
dialog.dismiss();
cartCount();
Toast.makeText(ShopDetailsActivity.this, "Order Placed Successfully...", Toast.LENGTH_SHORT).show();
prepareNotificationMessage(timestamp);
/*after placing order open order details page*/
/*open order details, we need two keys there, orderId and orderTo*/
//                        Intent intent = new Intent(ShopDetailsActivity.this, OrderDetailsUsersActivity.class);
//                        intent.putExtra("orderTo",shopUid);
//                        intent.putExtra("orderId",timestamp);
//                        startActivity(intent);

}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
/*failed to place order*/
progressDialog.dismiss();
Toast.makeText(ShopDetailsActivity.this, ""+e.getMessage(), Toast.LENGTH_SHORT).show();
}
});
}

Answer 1

我不熟悉EasyDb库，但可以肯定的是，它不会自动检查的重复

在addToCart函数中，您添加了代码的这一部分

Boolean b = easyDB.addData("Item_Id",itemId)
.addData("Item_PID",productId)
.addData("Item_Name",title)
.addData("Item_Price_Each",priceEach)
.addData("Item_Price",price)
.addData("Item_Quantity",quantity)
.doneDataAdding();

它将新项目添加到数据库中，但是您没有添加任何逻辑来检查该项目是否已经存在于数据库中。此外，通常insert数据不更新。因此，我的建议是，如果您在购物车中已经有一个物品的ArrayList，您可以通过逻辑检查该物品是否存在于ArrayList中。否则，您必须首先对数据库进行查询并返回结果，然后创建自己的逻辑来检查该项是否存在于数据库中。如果是，则应使用新编号update数据库，否则insert为新项目。