我的 sqlite 数据库只插入一项 android studio (java)答案

【问题标题】：My sqlite database is only inserting one item android studio (java)我的 sqlite 数据库只插入一项 android studio (java)
【发布时间】：2021-09-27 16:09:09
【问题描述】：

我不知道怎么做，但我的 sqlite 数据库似乎只能存储一项而不是很多。每当我添加一个项目时，我的数据库助手似乎都会返回 false。我该如何解决？

每次我将产品实例添加到数据库时，它都会返回 false 并且只保留一个项目，但不再添加任何项目。

这是我的产品类别：

public class ProductModel {
    private int id;
    private String name;
    private float price;
    private int quantity;
    private float total;
    private  int inBasket;

    public ProductModel(int id, String name, float price, int quantity, int inBasket) {
        this.id = id;
        this.name = name;
        this.price = price;
        this.quantity = quantity;
        this.total = this.price * this.quantity;
        this.inBasket = inBasket;
    }

    public  ProductModel(){

    }

    @Override
    public String toString() {
        String n = this.name.toUpperCase();
        return n + "\n Price:" + price + "\n Qty:" + quantity + "\n inBasket:"+inBasket+"\n Total:" + total;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public float getPrice() {
        return price;
    }

    public void setPrice(float price) {
        this.price = price;
    }

    public int getQuantity() {
        return quantity;
    }

    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }

    public float getTotal() {
        return total;
    }

    public void setTotal(float price, int quantity) {
        this.total = price * quantity;
    }

    public int getInBasket() {
        return inBasket;
    }

    public void setInBasket(int inBasket) {
        this.inBasket = inBasket;
    }
}

这是我的数据库助手：

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

import androidx.annotation.Nullable;

import java.util.ArrayList;
import java.util.List;

public class DataBaseHelper extends SQLiteOpenHelper {

    public static final String PRODUCT_TABLE = "PRODUCT_TABLE";
    public static final String COL_ID = "PRODUCT_ID";
    public static final String COL_NAME = "PRODUCT_NAME";
    public static final String COL_PRICE = "PRODUCT_PRICE";
    public static final String COL_QUANTITY = "PRODUCT_QUANTITY";
    public static final String COL_TOTAL = "PRODUCT_TOTAL";
    public static final String COL_IN_BASKET = "PRESENT_BASKET";

    public static final String CREATE_TABLE_QUERY = "CREATE TABLE "+ PRODUCT_TABLE +"(" +
            COL_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
            COL_NAME + " TEXT, " +
            COL_PRICE + " FLOAT, " +
            COL_QUANTITY + " INT, " +
            COL_TOTAL + " FLOAT, " +
            COL_IN_BASKET + " INT);";
    public DataBaseHelper(@Nullable Context context) {
        super(context, "ProductList.db", null, 1);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(CREATE_TABLE_QUERY);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { }

    public boolean addItem(ProductModel productModel){
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues cv = new ContentValues();
        cv.put(COL_ID, productModel.getId());
        cv.put(COL_NAME, productModel.getName());
        cv.put(COL_PRICE, productModel.getPrice());
        cv.put(COL_QUANTITY, productModel.getQuantity());
        cv.put(COL_TOTAL, productModel.getTotal());
        cv.put(COL_IN_BASKET, productModel.getInBasket());
        long insert = db.insert(PRODUCT_TABLE, null, cv);
        if(insert==-1){
            return false;
        }
        else { return true; }
    }

    public boolean deleteOne(ProductModel productModel){
        SQLiteDatabase db = this.getReadableDatabase();
        String QueryString = "DELETE FROM "+PRODUCT_TABLE+" WHERE " +COL_ID+ "=" +productModel.getId();
        Cursor cursor = db.rawQuery(QueryString, null);
        if(cursor.moveToFirst()){
            return true;
        }
        else{ return false; }
    }

    public List<ProductModel> getEverything(){
        List<ProductModel> returnList = new ArrayList<>();
        SQLiteDatabase db = this.getReadableDatabase();
        String QueryString = "SELECT * FROM " + PRODUCT_TABLE;
        Cursor cursor = db.rawQuery(QueryString, null);
        if(cursor.moveToFirst()){
            do{
                int productID = cursor.getInt(0);
                String productName = cursor.getString(1);
                float productPrice = cursor.getFloat(2);
                int productQuantity = cursor.getInt(3);
                int inBasket = cursor.getInt(5);

                ProductModel newProduct = new ProductModel(productID, productName, productPrice, productQuantity, inBasket);
                returnList.add(newProduct);

            }while(cursor.moveToNext());
        }else{ /*nothing*/ }
        //close both cursor & db when done
        cursor.close();
        db.close();
        return returnList;
    }
}

以及处理向数据库添加数据的相应活动：

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

public class MainActivity extends AppCompatActivity {
    Button bt_add;
    EditText et_name, et_price, et_qty;
    ListView lv_itemlist;
    ArrayAdapter productArrayAdapter;
    DataBaseHelper dataBaseHelper;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        bt_add = findViewById(R.id.bt_add);
        et_name = findViewById(R.id.et_name);
        et_price = findViewById(R.id.et_price);
        et_qty = findViewById(R.id.et_qty);
        lv_itemlist = findViewById(R.id.lv_itemlist);

        dataBaseHelper = new DataBaseHelper(MainActivity.this);
        ShowProductOnListView(dataBaseHelper);
        bt_add.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                ProductModel productModel = new ProductModel();
                try{
                    productModel.setId(-1);
                    productModel.setName(et_name.getText().toString());
                    productModel.setPrice(Float.parseFloat(et_price.getText().toString()));
                    productModel.setQuantity(Integer.parseInt(et_qty.getText().toString()));
                    productModel.setInBasket(1);//1 for true, 0 for false;
                    productModel.setTotal(productModel.getPrice(), productModel.getQuantity());
                    Log.d("CheckAdd" ,""+productModel.getTotal()); //checks if the total is in the product
                }
                catch (Exception e){
                    Log.d("CheckAdd" ,"Error on btn_add");
                }
                DataBaseHelper databaseHelper = new DataBaseHelper(MainActivity.this);
                boolean success = databaseHelper.addItem(productModel);
                Log.d("CheckAdd" ,"Success value:"+success);//expected true
                ShowProductOnListView(dataBaseHelper);
            }
        });
        lv_itemlist.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                ProductModel clickedProduct = (ProductModel) parent.getItemAtPosition(position);
                dataBaseHelper.deleteOne(clickedProduct);
                ShowProductOnListView(dataBaseHelper);
            }
        });
    }

    private void ShowProductOnListView(DataBaseHelper dataBaseHelper) {
        productArrayAdapter = new ArrayAdapter<ProductModel>(MainActivity.this, android.R.layout.simple_list_item_1,dataBaseHelper.getEverything());
        lv_itemlist.setAdapter(productArrayAdapter);
    }
}

【问题讨论】：

你会添加你的数据库架构吗？因为我的猜测是，您的 ID 字段必须是唯一的，并且您总是尝试添加具有相同 id (-1) 的新产品。
您需要更改 productModel.setId(-1) ，因为它添加了具有相同 id 的产品。即-1
@TheTanic 我认为我没有架构。我刚刚在 databasehelper 中声明了列字符串。我会尝试对 (-1) id 做一些事情
@Priyaank 我更正了它是 id()。谢谢
因为您在函数“addItem”中传递了一个项目，所以只添加了一个项目。使用循环或项目列表管理它。

标签： java android sqlite android-studio

【解决方案1】：

使用这个简单的设置数据到数据库或从数据库获取数据

private ContentValues modelToContentValue(Model model)
{
    ContentValues contentValues = new ContentValues();
    contentValues.put("Price" , model.getPrice());
   // And else ....
    return contentValues;
}


private ArrayList<Model> cursorToModel(Cursor cursor)
{
    ArrayList<Model> Models = new ArrayList<>();

    cursor.moveToFirst();
    while (!cursor.isAfterLast())
    {
        Model model = new Model();

        model.setPrice(cursor.getFloat(cursor.getColumnIndex("Price")));
        // And else ....
        models.add(model);
        cursor.moveToNext();
    }
    return models;
}

我用这个方法插入到表格中

public boolean insertGroup(ArrayList<Model> models)
{
    SQLiteDatabase db = dbHelper.getWritableDatabase();
    try
    {
        db.beginTransaction();
        for (Model model : models)
        {
            ContentValues contentValues = modelToContentValue(model);
            db.insertOrThrow("TableName" , null , contentValues);
        }
        db.setTransactionSuccessful();
        db.endTransaction();
        db.close();
        return true;
    }
    catch (Exception exception)
    {
        exception.printStackTrace();
        if (db.inTransaction())
        {
            db.endTransaction();
        }
        if (db.isOpen())
        {
            db.close();
        }
      
        return false;
    }
}

我用这个方法读表

public ArrayList<Model> getAll()
    {
        ArrayList<Model> models = new ArrayList<>();
        try
        {
    SQLiteDatabase db = dbHelper.getReadableDatabase();
            Cursor cursor = db.query("TableName", allColumns(), null, null, null, null, null);
            if (cursor != null)
            {
                if (cursor.getCount() > 0)
                {
                    models = cursorToModel(cursor);
                }
                cursor.close();
            }
            db.close();

catch (Exception exception)
        {
            exception.printStackTrace();
}

private String[] allColumns()
    {
        return new String[]
        {
            "Price",
            // and else ....
        };
    }

【讨论】：

【解决方案2】：

在bt_add的监听器内部，有这行：

productModel.setId(-1);

您将productModel 的ID 设置为-1。

然后，第一次执行代码时，插入的新行PRODUCT_ID 等于-1。
但是，对于任何随后对addItem() 的调用，插入都会失败，因为PRODUCT_ID 是表的PRIMARY KEY，这意味着它是唯一的，并且PRODUCT_ID 等于@987654331 的行不能超过1 行@.

列PRODUCT_ID，因为您将其定义为INTEGER PRIMARY KEY AUTOINCREMENT，所以插入代码中不需要任何值。这将由 SQLite 处理。

所以，从监听器中删除这一行：

productModel.setId(-1);

还有这一行：

cv.put(COL_ID, productModel.getId());

来自addItem()。

【讨论】：