SQLite是Android非常重要的数据存储方式,但是它的操作非常简单,今天就给大家简单讲一下:
先写一个DBHelper类,用来创建数据库表
package com.zking.db;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
/**
* Created by Administrator on 2017/6/25 0025.
*/
public class DbHelper extends SQLiteOpenHelper{
/**
*
* @param context 上下文
* @param name 数据库的名字,“文件名.db”
* @param factory 数据库工厂,null
* @param version 数据库版本
*/
public DbHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {
super(context, name, factory, version);
Log.i("test","构造方法");
}
//使用该方法:创建表
//只会调用一次
@Override
public void onCreate(SQLiteDatabase db) {
Log.i("test","创建表");
db.execSQL("create table login(uid integer primary key autoincrement,uname,upass)");
}
//数据库版本 低-->高
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.i("test","升级数据库版本");
}
// @Override
// public void onDowngrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// super.onDowngrade(db, oldVersion, newVersion);
// }
}
接下来讲一下如何写sql语句,以及如何调用DBHelper类
package com.zking.administrator.g160628_android16_sqlite;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.EditText;
import android.widget.Toast;
import com.zking.db.DbHelper;
public class MainActivity extends AppCompatActivity {
private SQLiteDatabase sqLiteDatabase;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
DbHelper dbHelper=new DbHelper(this,"G160628.db",null,2);//第二个参数是数据库的名字
sqLiteDatabase = dbHelper.getWritableDatabase();
}
public void operation(View view){
String uname=et_main_uname.getText().toString();
String upass=et_main_upass.getText().toString();
//添加 1
// ContentValues contentValues=new ContentValues();
// contentValues.put("uname",uname);
// contentValues.put("upass",upass);
// contentValues.putNull("uid");
// sqLiteDatabase.insert("login","uname",contentValues);
//添加2
// for (int i = 0; i <100 ; i++) {
// sqLiteDatabase.execSQL("insert into login(uname,upass) values('小"+i+"','123')");
// }
//修改
// ContentValues contentValues=new ContentValues();
// contentValues.put("uname",uname);
// contentValues.put("upass",upass);
// sqLiteDatabase.update("login",contentValues,"uid=?",new String[]{1+""});//因为需要一个String类型的数组,所以我们在使用int类型的数据时需要拼接一个“”
//删除
//sqLiteDatabase.delete("login","uid=?",new String[]{102+""});
//查询
// sqLiteDatabase.query()
int pageNo=2;
int pageSize=3;
Cursor cursor=sqLiteDatabase.rawQuery("select * from login limit ?,?",new String[]{((pageNo-1)*pageSize)+"",pageSize+""});//查询时需要使用游标接收
while (cursor.moveToNext()){
int uid=cursor.getInt(cursor.getColumnIndex("uid"));
String name=cursor.getString(cursor.getColumnIndex("uname"));
String pass=cursor.getString(cursor.getColumnIndex("upass"));
Log.i("test",uid+" "+name+" "+pass);
}
Toast.makeText(this, "操作OK", Toast.LENGTH_SHORT).show();
}
}