使用sqlite工具和Android代码的方式建立SQLite数据库。在完成建立数据库工作后，编程实现基本的数据库操作功能，包括数据的添加、删除、修改和更新。
学生信息管理案例:
①创建新工程
②创建一个包com.imau.dao 用来写数据库
名字 DBHelper
③再创建一个包com.imau.entity
名字为student
④再建一个com.imau.controller
名字为studentcontroller
⑥创建常量包：处理表的字段 com.imau.const
名字为const
实体student.java
package com.imau.entity
//与数据表对应：sql对象
public class student{
//主键
private int_id;
//姓名
private String sname;
//学号
private String sno;
//性别
private String sex;
public Student（int_id,String sname,String sno,String sex;）{
this._id=_id;
this.sname=sname;
this.sno=sno;
this.sex=sex;
}
public Student（）{
}
public int get_id(){
return_id;
}
public String getSname(){
return sname;
}
public String getSno(){
return sno;
}
public String getSex(){
return sex;
}
@Override
public String toString(){
return "Student{"+
"_id="+_id+
",sname='"+sname+'\''+
",sno='"+sno+'\''+
",sex='"+sex+'\''+
'}';
}
}
数据库代码DBHelper.java
package com.imau.entity
import android.R.integer;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
public class DBAdapter {
private final Context context;
private SQLiteDatabase db;
private DBHelper dbHelper;
private final static String DB_TABLE="studentinfo";
private final static String DB_NAME="student.db";
private final static int DB_VERSION=1;
private final static String KEY_ID="id";
private final static String KEY_SNO="sno";
private final static String KEY_SNAME="sname";
private final static String KEY_CLASSES="classes";
public DBAdapter(Context _cContext) {
// TODO Auto-generated constructor stub
context = _cContext;
}
//关闭数据库的连接
public void close()
{
if(db!=null)
{
db.close();
db=null;
}
}
public void open() throws SQLiteException
{
dbHelper = new DBHelper(context, DB_NAME, null, DB_VERSION);
try{
db = dbHelper.getWritableDatabase();
}catch(Exception e)
{
db = dbHelper.getReadableDatabase();
}
}
//插入数据
public long insert(Student s)
{
ContentValues cv = new ContentValues();
cv.put(KEY_SNO,s.getSno() );
cv.put(KEY_SNAME, s.getSname());
cv.put(KEY_CLASSES, s.getClasses());
return db.insert(DB_TABLE, null, cv);
}
//查询所有的数据
public Student[] findAllStudent()
{
Cursor c = db.query(DB_TABLE, null, null, null, null,null, null)
// while (c.moveToNext()) {
// System.out.println(c.getString(c.getColumnIndex("sno")));
//
// }
return convertToStudent(c);
}
public long deleteAllStudent()
{
return db.delete(DB_TABLE, null, null);
}
//这种方发比较好能够防止sql注入
public long deleteBySno(String sno)
{
return db.delete(DB_TABLE, "sno=?", new String[]{
sno});
}
//这种方式其实不太好存在sql注入的问题，但是一般的情况下是可以使用的
public long deleteBYId(int id)
{
return db.delete(DB_TABLE, "id="+id, null);
}
public Student[]
findStudentsBySno(String sno)
{
Cursor c = db.query(DB_TABLE, null, "sno=?", new String[]{
sno}, null, null, null);
return convertToStudent(c);
}
public long updateOneStudentById(int id,Student s)
{
ContentValues cv = new ContentValues();
cv.put(KEY_SNO, s.getSno());
cv.put(KEY_SNAME, s.getSname());
cv.put(KEY_CLASSES, s.getClasses());
return db.delete(DB_TABLE, cv, "id="+id, null);
}
public Student[] findOneStudentByID(int ID)
{
Cursor c = db.query(DB_TABLE, null, "id="+ID, null, null, null, null);
return convertTOStudent（c）;
}
//转换函数
public Student[] convertToStudent(Cursor c)
{
int resultsCount = c.getCount();
if(resultsCount==0||!c.moveToFirst())
{
return null
}
Student []stu = new Student[resultsCount];
for (int i = 0; i < stu.length; i++) {
stu[i] = new Student();
String sno = c.getString(c.getColumnIndex("sno"));
String sname = c.getString(c.getColumnIndex("sname"));
String sex = c.getString(c.getColumnIndex("sex"));
stu[i].id=c.getInt(0);
stu[i].setSno(sno);
stu[i].setSname(sname);
stu[i].setClasses(sex);
c.moveToNext();
}
return stu;
}
//内部的静态类用于创建数据库和建立数据库链接
private static class DBHelper extends SQLiteOpenHelper{
public DBHelper(Context context, String name, CursorFactory factory, int version) {
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
private static final String SQL="CREATE TABLE studentinfo ("
+ "id INTEGER PRIMARY KEY AUTOINCREMENT,"
+ "sno TEXT DEFAULT NONE,"
+ "sname TEXT DEFAULT NONE,"
+ "classes TEXT DEFAULT NONE"
+ ")";
@Override
public void onCreate(SQLiteDatabase db)
{
// TODO Auto-generated method stub
db.execSQL(SQL);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
db.execSQL("DROP TABLE IF EXISTS"+DB_TABLE);
oncreate（db）;
}
}
}
查洵:
public void queryAll(View view) {
StringBuffer buffer=new Str ingBuffer() ;
//查洵
Cursor cr = db. query( table: " user", columns: null, selection: null, selectionArgs: null, groupBy; null, having: null, orderBy: null) ;
//结果遍历
//判断是否有数据
if (cr!=null) {
while(cr. moveToNext() {
//取值
int id=cr. getInt ( columnIndex: 0) ;
String name=cr. getString( columnIndex: 1);
int age=cr. getInt ( columnIndex: 2) ;
buffer. append(id) ;
buffer. append(", ");
buffer. append (name) ;
buffer. append(",");
buffer. append(age) ;
buffer. append(" \n");
}
}
//关闭游标
cr. close() ;
db. close() ;
添加：
public void add(View view) {
//insert into table 0) values 0);
ContentValues values=new ContentValues() ;
values. put(" name", "CCC");
db. insert( table:”user", nullColumnHack: null, values);
}
删除：
public void delete(View view) {
db=he lper. getWri tableDatabase() ;
int row= db. delete( table: "user", whereClause:”age = ?” , new String[]{
"20"});
System. out. println(" row-==”+row);
db. close();
修改：
public void update(View view) {
db=helper. getWritableDatabase();
ContentValues values=new ContentValues();
values. put(" name", "DD");
db. update( table:" user' , values, whereClause: age= ?" , new String[]{
"28' });
db. close();
效果如图：
