数据库

//创建数据库
package com.example.yuekao.dbutil;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;

public class DataHelper extends SQLiteOpenHelper {

//数据库名public static final String DATA_NAME="accesscon.db";//表名public static final String TABLE_NAME="conr";public DataHelper(Context context) {    super(context, DATA_NAME, null, 1);}@Overridepublic void onCreate(SQLiteDatabase db) {    //创建数据库    db.execSQL("create table if not exists "+TABLE_NAME+" (_id integer primary key autoincrement,username text,tel text)");}@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}

//数据库的增删改查
package com.example.yuekao.dbutil;
import java.util.ArrayList;
import java.util.List;

import com.example.yuekao.vo.User;

import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class DBmanager {
DataHelper helper;
SQLiteDatabase db;
public DBmanager(Context context) {
super();
helper=new DataHelper(context);
db=helper.getWritableDatabase();
}

//添加public void add(List<User> users){    try {        db.beginTransaction();        for (User user : users) {            ContentValues values=new ContentValues();            values.put("username", user.getUsername());            values.put("tel", user.getTel());            db.insert(DataHelper.TABLE_NAME, null, values);        }        db.setTransactionSuccessful();    } catch (Exception e) {        // TODO: handle exception    }finally{        db.endTransaction();    }}//查询public List<User> select(){    List<User> users=new ArrayList<>();    Cursor cursor=db.query(DataHelper.TABLE_NAME, null, null, null, null, null, null);    while(cursor.moveToNext()){        User user=new User();        user.setId(cursor.getInt(cursor.getColumnIndex("_id")));        user.setUsername(cursor.getString(cursor.getColumnIndex("username")));        user.setTel(cursor.getString(cursor.getColumnIndex("tel")));        users.add(user);    }    cursor.close();    return users;}//删除public void delete(int id){    db.delete(DataHelper.TABLE_NAME, "_id = "+id, null);    select();}

}

//让项目启动的时候就运行，增删改查的方法直接调用
package com.example.yuekao.dbutil;

import android.app.Application;

public class TestManager extends Application {
public static DBmanager dbmanager;
@Override
public void onCreate() {
super.onCreate();
dbmanager=new DBmanager(getApplicationContext());
}
}