Android SQLite数据库操作实例

Android的自带数据库SQLite小巧且功能强大，Android提供了两种方式去操作数据库，第一种是用SQL语句去操作数据，SQLite支持标准的SQL，其分页等操作与Mysql一样，以下是利用SQL操作SQLite：

import java.util.ArrayList;
import java.util.List;

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

public class PersonDaoClassic {
private DBOpenHelper helper;

public PersonDaoClassic(Context context) {
helper = new DBOpenHelper(context);
}

public void insert(Person p) {
// 打开可写数据库
SQLiteDatabase db = helper.getWritableDatabase();

// 执行SQL语句, 替换占位符
db.execSQL("INSERT INTO person(name, balance) VALUES(?, ?)", new Object[] { p.getName(), p.getBalance() });

// 释放资源
db.close();
}

public void delete(int id) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("DELETE FROM person WHERE id=?", new Object[] { id });
db.close();
}

public void update(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();
db.execSQL("UPDATE person SET name=?, balance=? WHERE id=?", new Object[] { p.getName(), p.getBalance(), p.getId() });
db.close();
}

public Person query(int id) {
SQLiteDatabase db = helper.getReadableDatabase();

// 执行原始查询, 得到一个Cursor(类似ResultSet)
Cursor c = db.rawQuery("SELECT name, balance FROM person WHERE id=?", new String[] { String.valueOf(id) });
Person p = null;

// 判断Cursor是否有下一条记录
if (c.moveToNext())
// 从Cursor中获取数据, 创建Person对象
p = new Person(id, c.getString(0), c.getInt(1));

// 释放资源
c.close();
db.close();
return p;
}

public List<Person> queryAll() {
SQLiteDatabase db = helper.getReadableDatabase();
Cursor c = db.rawQuery("SELECT id, name, balance FROM person", null);
List<Person> persons = new ArrayList<Person>();
while (c.moveToNext())
persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
c.close();
db.close();
return persons;
}

public List<Person> queryPage(int pageNum, int capacity) {
// 开始索引
String start = String.valueOf((pageNum - 1) * capacity);
// 查询的个数
String length = String.valueOf(capacity);

SQLiteDatabase db = helper.getReadableDatabase();

// 翻页查询语句, 和MySQL中相同
Cursor c = db.rawQuery("SELECT id, name, balance FROM person LIMIT ?,?", new String[]{start, length});
List<Person> persons = new ArrayList<Person>();
while (c.moveToNext())
persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
c.close();
db.close();
return persons;
}

public int queryCount() {
SQLiteDatabase db = helper.getReadableDatabase();

// 查询记录条数
Cursor c = db.rawQuery("SELECT COUNT(*) FROM person", null);
c.moveToNext();
int count =c.getInt(0);
c.close();
db.close();
return count;
}

}

除上述方法以外，android还给我们带来了另外一种更加简单，也是android推荐使用的一种方式，此种方式把数据封装在ContentValues中，因为android编程过程中经常会使用到已经封装好了数据的ContentValues，所以使用第二种方式在有些时候更加便捷，以下是代码：

package cn.itcast.sqlite;

import java.util.ArrayList;
import java.util.List;

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

public class PersonDao {
private DBOpenHelper helper;

public PersonDao(Context context) {
helper = new DBOpenHelper(context);
}

public void remit(int from, int to, int amount) {
SQLiteDatabase db = helper.getWritableDatabase();

// 开启事务
db.beginTransaction();
try {
db.execSQL("UPDATE person SET balance=balance-? WHERE id=?", new Object[]{amount, from});
db.execSQL("UPDATE person SET balance=balance+? WHERE id=?", new Object[]{amount, to});
db.setTransactionSuccessful();
} catch (Exception e) {
e.printStackTrace();
}
// 结束事务, 将事务成功点前面的代码提交
db.endTransaction();

db.close();
}

public void insert(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();

// 准备数据
ContentValues values = new ContentValues();
values.put("name", p.getName());
values.put("balance", p.getBalance());

// 通过ContentValues中的数据拼接SQL语句, 执行插入操作, id为表中的一个列名
db.insert("person", "id", values);

db.close();
}

public void delete(int id) {
SQLiteDatabase db = helper.getWritableDatabase();

// 执行删除操作, 在person表中删除id为指定值的记录
db.delete("person", "id=?", new String[]{String.valueOf(id)});

db.close();
}

public void update(Person p) {
SQLiteDatabase db = helper.getWritableDatabase();

// 要更新的数据
ContentValues values = new ContentValues();
values.put("name", p.getName());
values.put("balance", p.getBalance());

// 更新person表中id为指定值的记录
db.update("person", values, "id=?", new String[] { String.valueOf(p.getId()) });

db.close();
}

public Person query(int id) {
SQLiteDatabase db = helper.getReadableDatabase();

// 执行查询: 不去重复, 表是person, 查询name和balance两列, Where条件是"id=?", 占位符是id, 不分组, 没有having, 不排序, 没有分页
Cursor c = db.query(false, "person", new String[]{"name", "balance"}, "id=?", new String[]{String.valueOf(id)}, null, null, null, null);

Person p = null;
// 判断Cursor是否有下一条记录
if (c.moveToNext())
// 从Cursor中获取数据, 创建Person对象
p = new Person(id, c.getString(0), c.getInt(1));

// 释放资源
c.close();
db.close();
return p;
}

public List<Person> queryAll() {
SQLiteDatabase db = helper.getReadableDatabase();

// 查询所有记录, 倒序
Cursor c = db.query(false, "person", new String[]{"id","name", "balance"}, null, null, null, null, "id DESC", null);

List<Person> persons = new ArrayList<Person>();
while (c.moveToNext())
persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
c.close();
db.close();
return persons;
}

public List<Person> queryPage(int pageNum, int capacity) {
// 开始索引
String start = String.valueOf((pageNum - 1) * capacity);
// 查询的个数
String length = String.valueOf(capacity);

SQLiteDatabase db = helper.getReadableDatabase();

// 翻页查询
Cursor c = db.query(false, "person", new String[]{"id","name", "balance"}, null, null, null, null, null, start + "," + length);

List<Person> persons = new ArrayList<Person>();
while (c.moveToNext())
persons.add(new Person(c.getInt(0), c.getString(1), c.getInt(2)));
c.close();
db.close();
return persons;
}

public int queryCount() {
SQLiteDatabase db = helper.getReadableDatabase();

// 查询记录条数
Cursor c = db.query(false, "person", new String[]{"COUNT(*)"}, null, null, null, null, null, null);

c.moveToNext();
int count =c.getInt(0);
c.close();
db.close();
return count;
}

}