BOLB stands for binary large object, which is a data type used to store pictures, images, videos, etc.
First, the use of scenarios:
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The public class MySQLiteOpenHelper extends SQLiteOpenHelper {
1, override the constructor
Public MySQLiteOpenHelper (Context, string name,
CursorFactory cursor, int version) (
Super (context, name, cursor, version);
}
2, the method of creating a database
public void onCreate(SQLite database db){
3. Create a database with table name: imagetable and fields: _id, image.
db . exec SQL(" CREATE TABLE image TABLE(_ id INTEGER PRIMARY KEY auto increment，image BLOB)")；
}
4, the method of updating the database
public void on upgrade(SQLite database db，int oldVersion，int newVersion) {
}
}
5. Create an instance of the helper class.
The value of CursorFactory is null, which means the default factory class is adopted.
mySQLiteOpenHelper = new mySQLiteOpenHelper(this，" saveimage.db "，null， 1)；
6. Create a readable database.
mydb = mysqliteopenhelper . getwritabledatabase()；
7. Convert the picture into a bitmap.
bitmap bitmap 1 = bitmapfactory . decode resource(get resources()，r . drawable . erweima)；
int size = bitmap 1 . getwidth()* bitmap 1 . getheight()* 4；
//Create a byte array output stream with size.
ByteArrayOutputStream baos = new ByteArrayOutputStream(size)；
//Set the bitmap compression format with the quality of 100%, and put it into the output stream of byte array bitmap1.compress (bitmap.compresseformat.png, 100, baos);
//Convert byte array output stream into byte array byte[]
byte[]image data 1 = baos . tobytearray()；
//Save the byte array to the database.
content values cv = new content values()；
cv.put("_id "， 1)；
cv.put("image "，imagedata 1)；
mydb.insert("imagetable "，null，cv)；
//Close the byte array output stream
baos . close()；
Second, the query method from the database:
1, create a pointer.
cursor cur = mydb . query(" imagetable "，new String[]{"_id "，" image"}，null，null，null，null，null)；
byte[]image query = null；
if(cur.moveToNext()){
2. convert Blob data into byte array imagequery = cur.getblob (cur.getcolumnindex ("image"));
}
3. Convert byte array into bitmap.
bitmap image bitmap = bitmap factory . decodebytearray(imagequery，0，image query . length)；
iv 1 =(ImageView)findViewById(r . id . ImageView 1)；
4. Display the bitmap as a picture.
iv 1 . setimagebitmap(image bitmap)；