Introduction to SQLite:
SQLite is an open source lightweight relational database used by the Android system. Android allows each application to have its own independent database. The location of each application's database is generally in/data/data/<package_name>/databasesmiddle. In order to facilitate developers' use, Android's API has encapsulated the addition, deletion, and revision. The SQLiteOpenHelper class can easily implement the creation and management of databases. However, before formally using the database, we need to know two basic knowledge points.
Content Values and Cursor:
Content Values are represented in the form of key-value pairs and are used to insert new rows into the database table. Each ContentValues is mapped to fields in the database and corresponding values.
Cursor is the way to return when querying SQLite data in Android. It is actually a pointer to the result set in the underlying data. It does not provide extracting and returning a copy of the result worth. In short, Cursor provides a convenient and easy-to-management way to control the position (row) of the pointer in the result set.
For Cursors, there are often the following methods to control the position of Cursor cursors in the underlying data result set, and they are:
01. moveToFirst(): Move the cursor to the first row in the query result set.
02. moveToNext(): Move the cursor to the next line.
03. moveToPrevious(): Move the cursor to the previous line
04. getCount(): Returns the number of rows in the query result set
05. getColumnIndexOrThrow(): Returns the index of the column with the specified name. Note: The index starts from 0. If there is no column with the name, an exception will be thrown.
06. getColumnName(): Returns the name of the specified column index.
07. getColumnNames(): Returns a string array of all column names in the current query result set.
08. moveToPosition(): Move the cursor to the specified row.
09. getPosition(): Returns the current cursor position.
Create and operate SQLite databases simply:
1. We can implement a customized SQLite help class by customizing our own SQLite class and allowing it to inherit the SQLiteOpenHelper class.
2. Rewrite its constructor, onCreate() and onUpgrade() methods to process the creation of a new database and upgrade to a new database respectively.
The above is an introduction to the SQLite database in Android introduced to you by the editor. I hope it will be helpful to you. If you have any questions, please leave me a message and the editor will reply to you in time!