通过ContentValues

Question

我正在尝试在Sqlite Db中存储和检索图像数据。

为此，我首先在本地设备内存中存储了一个示例pic（路径：storage / emulated / 0 / Download /）。

public class MainActivity extends AppCompatActivity implements LoaderManager.LoaderCallbacks<Cursor> {

    private final String SAMPLE_IMAGE_PATH = "/storage/emulated/0/Download/image.jpg";

然后我设置了一个insert方法来为db提供这些示例数据：

 private void insertProduct() {
    // Create a ContentValues object where column names are the keys,
    // and sample attributes are the values.

    ContentValues values = new ContentValues();
    values.put(InventoryContract.ProductEntry.COLUMN_PRODUCT_NAME, sampleName);
    values.put(InventoryContract.ProductEntry.COLUMN_PRODUCT_QTY, sampleQty);
    values.put(InventoryContract.ProductEntry.COLUMN_PRODUCT_PRICE, SamplePrice);
    values.put(InventoryContract.ProductEntry.COLUMN_EMAIL, sampleMail);
    values.put(InventoryContract.ProductEntry.COLUMN_PHONE, samplePhone);
    values.put(InventoryContract.ProductEntry.COLUMN_PRODUCT_PIC, SAMPLE_IMAGE_PATH);

    //insert a new row
    Uri newUri = getContentResolver().insert(InventoryContract.ProductEntry.CONTENT_URI,values);
}

我定义onCreateLoader方法如下：

public Loader<Cursor> onCreateLoader(int id, Bundle args) {
    // Define a projection that specifies the columns from the table we care about.
    String[] projection = {
            InventoryContract.ProductEntry._ID,
            InventoryContract.ProductEntry.COLUMN_PRODUCT_PIC,
            InventoryContract.ProductEntry.COLUMN_PRODUCT_PRICE,
            InventoryContract.ProductEntry.COLUMN_PRODUCT_QTY,
            InventoryContract.ProductEntry.COLUMN_PRODUCT_NAME};

    // This loader will execute the ContentProvider's query method on a background thread
    return new CursorLoader(this,   
            InventoryContract.ProductEntry.CONTENT_URI,   
            projection,
            null,      
            null,                   
            null);                  
}

在CursorAdapter类中，我更新了listView，在bindView（）方法中从db添加数据：

 public void bindView(View view, Context context, Cursor cursor) {

    // Find individual views that we want to modify in the list item layout
    TextView nameTextView = (TextView) view.findViewById(R.id.prod_name);
    TextView priceTextView = (TextView) view.findViewById(R.id.prod_price);
    TextView qtyTextView = (TextView) view.findViewById(R.id.prod_qty);
    ImageView prodImageView = (ImageView) view.findViewById(R.id.prod_img);

    // Find the columns of attributes that we're interested in
    int nameColumnIndex = cursor.getColumnIndex(InventoryContract.ProductEntry.COLUMN_PRODUCT_NAME);
    int priceColumnIndex = cursor.getColumnIndex(InventoryContract.ProductEntry.COLUMN_PRODUCT_PRICE);
    int qtyColumnIndex = cursor.getColumnIndex(InventoryContract.ProductEntry.COLUMN_PRODUCT_QTY);
    int picColumnIndex = cursor.getColumnIndex(InventoryContract.ProductEntry.COLUMN_PRODUCT_PIC);

    // Read the attributes from the Cursor for the current product
    String prodName = cursor.getString(nameColumnIndex);
    Double prodPrice = cursor.getDouble(priceColumnIndex);
    int prodQty = cursor.getInt(qtyColumnIndex);
    byte [] prodImg = cursor.getBlob(picColumnIndex);

    BitmapFactory.Options options = new BitmapFactory.Options();
    options.inTempStorage = new byte[1024 * 32];

    Bitmap bmp = BitmapFactory.decodeByteArray(prodImg, 0, prodImg.length, options);


    //Update Views
    nameTextView.setText(String.valueOf(prodName));
    priceTextView.setText(prodPrice.toString());
    qtyTextView.setText(String.valueOf(prodQty));
    prodImageView.setImageBitmap(bmp);
}
}

当我尝试执行此代码时，一切正常，但我看到的是空白图像，而不是选定的图片和放置图片。

所以我认为将数据插入数据库存在一些问题。

Answer 1

  

我正在尝试在Sqlite Db中存储和检索图像数据

我不推荐这个。将图像存储在文件中。将数据存储在标识文件的行中。

  

然后我设置了一个insert方法，用这些示例数据

为db提供数据

您正在COLUMN_PRODUCT_PIC中存储字符串。您没有存储byte[]。相对于我的建议，这很好。这与您的数据检索代码有关，您尝试检索byte[]。