无法从 android 中的 SQLite 检索数据

Question

我正在制作一个电子商务应用程序。在这个应用程序中，我制作了一个表格，其中存储了产品的以下详细信息：

• 产品的三张图片；
• 姓名；
• 价格；
• 说明；
• 产品材料的单位（如公斤、升、克等）。

添加产品效果很好，但我在检索数据时遇到了问题。 确切的问题是，每当我尝试使用查询SELECT * FROM productsBox 从表中检索整个数据时，它既没有返回任何内容，也没有给我任何错误，只是从数据库返回零行。我试图通过手动编写所有列名而不是 * 来检索数据，但遇到了同样的问题。 最重要的一点是，只有当我试图获取“image3”列时才会发生这种情况。我不知道为什么，但是这个专栏有问题。

数据库类

public class AddProductDatabase extends SQLiteOpenHelper {
    public AddProductDatabase(@Nullable Context context) {
        super(context, "products.db", null, 9);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        String createTableStatement = "CREATE TABLE products (id INTEGER PRIMARY KEY AUTOINCREMENT , image1 BLOB , image2 BLOB , image3 BLOB , productName TEXT ,productPrice INTEGER , unit TEXT, productDescription TEXT) ";
        db.execSQL(createTableStatement);
    }

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

      /* String createTableStatement = "CREATE TABLE category (id INTEGER PRIMARY KEY AUTOINCREMENT , image1 BLOB,catName TEXT) ";
        db.execSQL(createTableStatement);
        String createTableStatement2 = "CREATE TABLE productsBox (id INTEGER PRIMARY KEY AUTOINCREMENT , image1 BLOB , image2 BLOB , image3 BLOB , productName TEXT ,productPrice INTEGER , unit TEXT, productDescription TEXT) ";
        db.execSQL(createTableStatement2);*/
      //  String createTableStatement2 = "CREATE TABLE profile (id INTEGER PRIMARY KEY AUTOINCREMENT , profileImage BLOB ,name TEXT ,phone INTEGER ,address TEXT,pincode INTEGER,role INTEGER,passw TEXT) ";
       // db.execSQL(createTableStatement2);
        String createTableStatement2 = "CREATE TABLE UserProfile (id INTEGER PRIMARY KEY AUTOINCREMENT , profileImage BLOB ,name TEXT ,phone TEXT ,address TEXT,pincode INTEGER,role INTEGER,passw TEXT) ";
        db.execSQL(createTableStatement2);
    }

    public boolean addProduct(ArrayList<byte[]> img, String name, int price, String unit, String description) {
        SQLiteDatabase db = this.getWritableDatabase();
        ContentValues cv = new ContentValues();
        cv.put("image1", img.get(0));
        cv.put("image2", img.get(1));
        cv.put("image3", img.get(2));
        cv.put("productName", name);
        cv.put("productPrice", price);
        cv.put("productDescription", description);
        cv.put("unit", unit);
        long products = db.insert("productsBox", null, cv);
        db.close();
        if (products == -1) {
            return false;
        } else {
            return true;
        }

    }


    public ArrayList<productmodal> getAll() {
        ArrayList<productmodal> array = new ArrayList<>();
        String querySelect = "SELECT id,image1,image2,productName,productPrice,productDescription,unit FROM productsBox";
        SQLiteDatabase dbb = this.getReadableDatabase();
        Cursor cursorSelect = dbb.rawQuery(querySelect, null);
       // DatabaseUtils.dumpCursor(cursorSelect);
        int ind_image = cursorSelect.getColumnIndex("image1");
        int ind_productName = cursorSelect.getColumnIndex("productName");
        int ind_productPrice = cursorSelect.getColumnIndex("productPrice");
        int ind_id = cursorSelect.getColumnIndex("id");
        int ind_desc = cursorSelect.getColumnIndex("productDescription");
        int ind_unit = cursorSelect.getColumnIndex("unit");
        int ind_img3 = cursorSelect.getColumnIndex("image2");


        if (cursorSelect.moveToFirst()) {
            do {
                byte[] image = cursorSelect.getBlob(ind_image);
                String name = cursorSelect.getString(ind_productName);
                int price = cursorSelect.getInt(ind_productPrice);
                int id = cursorSelect.getInt(ind_id);
                productmodal model = new productmodal(image, name, price,id);
                array.add(model);
            } while (cursorSelect.moveToNext());
        } else {

        }
        cursorSelect.close();
        dbb.close();
        return array;
    }

    public ArrayList<productDetailModal> getProduct(int idd) {
        ArrayList<productDetailModal> array = new ArrayList<>();
        String querySelect = "SELECT id,image1,image2,image3,productName,productPrice,productDescription,unit FROM productsBox WHERE id ="+idd;
        SQLiteDatabase dbb = this.getReadableDatabase();
        Cursor cursorSelect = dbb.rawQuery(querySelect, null);
        DatabaseUtils.dumpCursor(cursorSelect);
        int ind_unit = cursorSelect.getColumnIndex("unit");
        int ind_productName = cursorSelect.getColumnIndex("productName");
        int ind_productPrice = cursorSelect.getColumnIndex("productPrice");
        int ind_id = cursorSelect.getColumnIndex("id");
        int ind_img1 = cursorSelect.getColumnIndex("image1");
        int ind_img2 = cursorSelect.getColumnIndex("image2");
        int ind_img3 = cursorSelect.getColumnIndex("image3");
        int ind_desc = cursorSelect.getColumnIndex("productDescription");

        if (cursorSelect.moveToFirst()) {
            do {
                String name = cursorSelect.getString(ind_productName);
                int price = cursorSelect.getInt(ind_productPrice);
                int id = cursorSelect.getInt(ind_id);
                byte[] proimg1= cursorSelect.getBlob(ind_img1);
                byte[] proimg2= cursorSelect.getBlob(ind_img2);
                byte[] proimg3= cursorSelect.getBlob(ind_img3);
                String desc = cursorSelect.getString(ind_desc);
                String unit = cursorSelect.getString(ind_unit);

                productDetailModal model = new productDetailModal(id,price,name,desc,unit ,proimg1,proimg2,proimg3);
                array.add(model);
            } while (cursorSelect.moveToNext());
        } else {

        }
        cursorSelect.close();
        dbb.close();
        return array;
    }

}

这里 getALL() 方法工作正常，因为我没有添加 image3 列，但 getProduct() 没有返回任何内容，因为这里我添加了 image3 列。

productDetailModal类

public class productDetailModal {
    int idd, price;
    String productname, productdesc,productunit;
    byte[] img1,img2,img3;

    public productDetailModal(int idd, int price, String productname, String productdesc, String productunit, byte[] img1, byte[] img2, byte[] img3) {
        this.idd = idd;
        this.price = price;
        this.productname = productname;
        this.productdesc = productdesc;
        this.productunit = productunit;
        this.img1 = img1;
        this.img2 = img2;
        this.img3 = img3;
    }

    public int getIdd() {
        return idd;
    }

    public void setIdd(int idd) {
        this.idd = idd;
    }

    public int getPrice() {
        return price;
    }

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

    public String getProductname() {
        return productname;
    }

    public void setProductname(String productname) {
        this.productname = productname;
    }

    public String getProductdesc() {
        return productdesc;
    }

    public void setProductdesc(String productdesc) {
        this.productdesc = productdesc;
    }

    public String getProductunit() {
        return productunit;
    }

    public void setProductunit(String productunit) {
        this.productunit = productunit;
    }

    public byte[] getImg1() {
        return img1;
    }

    public void setImg1(byte[] img1) {
        this.img1 = img1;
    }

    public byte[] getImg2() {
        return img2;
    }

    public void setImg2(byte[] img2) {
        this.img2 = img2;
    }

    public byte[] getImg3() {
        return img3;
    }

    public void setImg3(byte[] img3) {
        this.img3 = img3;
    }
}

productModal类

public class productmodal {

    byte[] productImage;
    String productName;
    int productPrice , id ;

    public productmodal(byte[] productImage, String productName, int productPrice, int id) {
        this.productImage = productImage;
        this.productName = productName;
        this.productPrice = productPrice;
        this.id = id;
    }

    public byte[] getProductImage() {
        return productImage;
    }

    public void setProductImage(byte[] productImage) {
        this.productImage = productImage;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public int getProductPrice() {
        return productPrice;
    }

    public void setProductPrice(int productPrice) {
        this.productPrice = productPrice;
    }

    public int getId() {
        return id;
    }

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

会不会是数据的大小有问题？像“不允许从数据库 SQLite 中检索更大尺寸的数据”类型的规则之类的？

Answer 1

会不会是数据的大小有问题？比如“不允许从数据库 SQLite 中检索更大尺寸的数据”类型的规则之类的？

这可能是并且很可能是问题所在。 CursorWindow 的大小有一个限制，最大为 4Mb，如果一行不适合 CursorWindow，那么即使数据存在于数据库中，也无法将其提取为单行。

因此，它不是 SQLite 限制，而是 Android API 的限制。

建议的解决方法是不在数据库中存储图像，而是将图像存储为文件并存储文件的路径（或足以确定从何处检索图像的路径的一部分） .

您可能希望考虑以下链接，深入研究该领域并提供潜在的解决方案：-

• How to use images in Android SQLite that are larger than the limitations of a CursorWindow?

• How can I insert image in a sqlite database