Simple application of Wang Liping--sqlite,sqliteopenhelper

The Android platform provides us with a database helper class to create or open a database, which inherits from the Sqliteopenhelper class, in which the constructor of the class invokes a method in the context to create and open a database object of the specified name. The main task of inheriting and extending the Sqliteopenhelper class is to rewrite the following two methods.

public class Mysqlitehelper extends Sqliteopenhelper {
Public Mysqlitehelper (Context context, String name, Cursorfactory factory,
int version) {
Super (context, name, Factory, version);
TODO auto-generated Constructor stub
}
This method is executed when the database is first created, where initialization such as creating tables is typically done here
Execsql Creating a Table
@Override
public void OnCreate (Sqlitedatabase db) {
TODO auto-generated Method Stub
Create a table
String sql= "CREATE table if not exists hero_info (" + "ID of integer primary key," + "name varchar," + "level integer)";
Db.execsql (SQL);
}
@Override
public void Onupgrade (sqlitedatabase db, int oldversion, int newversion) {
TODO auto-generated Method Stub

}

Mainactivity.java

Package Com.example.sqllite;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import Android.graphics.Color;
import Android.os.Bundle;
import Android.widget.TextView;
Public class Mainactivity extends Activity {
private TextView TV;
private mysqlitehelper H;


@Override
protected void OnCreate (Bundle savedinstancestate) {
super.oncreate (savedinstancestate);
Setcontentview (r.layout.activity_main);
init ();
    }
Public void Init () {
     tv= (TextView) Findviewbyid (r.id.tv);
    h=new Mysqlitehelper (This, "my.db", NULL, 1);
    insertandupdatedata (h);
    //Query data
    String result = Querydata (h);
    Tv.settextcolor (color.red);
    tv.settextsize (20.0f);
    Tv.settext ("The name \ t level \ n" +result);
   
   
    }
    
 
private void Insertandupdatedata (Mysqlitehelper helper) {
//TODO auto-generated method stub

//calling the Getreadabledatabase method does not always return a read-only database object .
//in general, this method is the same as the return of the Getwriteabledatabase method,
//A read-only database object is returned only if the database is open only for read-only permissions or when the disk is full.

    Sqlitedatabase db = Helper.getwritabledatabase ();
    //Use the Execsql method to insert data into the table
    Db.execsql ("INSERT into Hero_info (name,level) VALUES (' BB ', 0)");
    //Insert data into a table using the Insert method
    contentvalues values = new Contentvalues ();
    values.put ("name", "XH");
    values.put ("level", 5);
    //Call method to insert data
    Db.insert ("Hero_info", "id", values);
    //Update the data in the table using the Update method
    //emptying the Contentvalues object
    values.clear ();
    values.put ("name", "XH");
    values.put ("level", ten);
    //Update XH at level
    db.update ("Hero_info", values, "level = 5", null);
    //Close Sqlitedatabase object
    db.close ();

} 
//Querying data from the database
Public String Querydata (mysqlitehelper myhelper) {
String result = "";
//Get database Objects
Sqlitedatabase db = Myhelper.getreadabledatabase ();
//Query the data in the table
cursor cursor = db.query ("Hero_info", NULL, NULL, NULL, NULL, NULL, "ID ASC");
//Gets the index of the name column
int nameindex = Cursor.getcolumnindex ("name");
//Gets the index of the level column
int levelindex = Cursor.getcolumnindex ("level");
For (Cursor.movetofirst ();! (Cursor.isafterlast ()); Cursor.movetonext ()) {
result = result + cursor.getstring (nameindex) + "\t\t";
result = result + Cursor.getint (levelindex) + "\ n";
}
cursor.close ();//close result set
db.close ();//Close database objects
return result;
}
@Override
protected void OnDestroy () {
Sqlitedatabase db = H.getwritabledatabase ();//Get Database object
//Delete all data in the Hero_info table 1 means delete all rows------> Click the Back button
db.delete ("Hero_info", "1", null);
Super.ondestroy ();
}
} 

Simple application of Wang Liping--sqlite,sqliteopenhelper