android cursor.getBlob无法正常工作 [英] android cursor.getBlob not working

问题描述

我试图在sqlite数据库中存储图像并从中检索图像.我的以下代码无法正常工作.我不确定我做错了什么.请帮忙. 我创建了数据库表，如下所示:

Hi I tried to store and retrieve image to and from sqlite database. My following codes is not working. I'm not sure what wrong I did. Please help. I created the database table as follows:

db = openOrCreateDatabase("StudentDB", Context.MODE_PRIVATE, null);
db.execSQL("CREATE TABLE IF NOT EXISTS student(rollno VARCHAR,
 name VARCHAR,photo BLOB,marks VARCHAR);");

然后我插入字段

db.execSQL("INSERT INTO student VALUES('" + editRollno.getText() + "','" + editName.getText() + "','" + imageInByte + "','" + editMarks.getText() + "');");

db.execSQL("INSERT INTO student VALUES('" + editRollno.getText() + "','" + editName.getText() + "','" + imageInByte + "','" + editMarks.getText() + "');");

其中imageInByte是一个byte []变量，它是从画廊之前分配的，如下所示:

where imageInByte is a byte[] variable which was assigned before from gallery as follows:

ByteArrayOutputStream stream = new ByteArrayOutputStream();
            yourImage.compress(Bitmap.CompressFormat.PNG, 100, stream);
            imageInByte = stream.toByteArray();

当我尝试从数据库中检索图像时，它失败了:

when I tried to retrieve an image from db it fails:

Cursor c = db.rawQuery("SELECT * FROM student WHERE rollno='"
                + editRollno.getText() + "'", null);
        if (c.moveToFirst()) {
            editName.setText(c.getString(1));
            editMarks.setText(c.getString(2));

            byte[] image = c.getBlob(3);
            ByteArrayInputStream imageStream = new ByteArrayInputStream(image);
            theImage = BitmapFactory.decodeStream(imageStream);     
            imageView2.setImageBitmap(theImage);

        }

推荐答案

您不能简单地将字节数组视为文本. (要将blob与execSQL一起使用，则必须使用blob文字.)

You cannot simply treat byte arrays as text. (To use blobs with execSQL, you would have to use blob literals.)

要插入行，请使用

To insert a row, use the insert method, which has support for byte arrays.

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