安卓之SQLite知识

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我是靠谱客的博主跳跃红牛，这篇文章主要介绍安卓之SQLite知识，现在分享给大家，希望可以做个参考。

1.SQLite介绍

SQLite是一款轻量级的数据库，是遵守ACID的关联式数据库管理系统，它的设计目标是嵌入式的，而且目前已经在很多嵌入式产品中使用了它，它占用资源非常的低，在嵌入式设备中，可能只需要几百K的内存就够了。它能够支持 Windows/Linux/Unix等等主流的操作系统，同时能够跟很多程序语言相结合，比如Tcl、PHP、Java、C++、.Net等，还有ODBC接口，同样比起 Mysql、PostgreSQL这两款开源世界著名的数据库管理系统来讲，它的处理速度比他们都快。

2.SQLite的有点

SQLite 只需要带一个动态库，就可以享受它的全部功能，而且那个动态库的尺寸想当小。

SQLite 数据库的核心引擎不需要依赖第三方软件，也不需要所谓的“安装”。
SQLite 数据库中所有的信息（比如表、视图、触发器等）都包含在一个文件夹内，方便管理和维护。
SQLite 目前支持大部分操作系统，不至电脑操作系统更在众多的手机系统也是能够运行，比如：Android。
SQLite 数据库支持多语言编程接口。
SQLite 数据库通过数据库级上的独占性和共享锁来实现独立事务处理。这意味着多个进程可以在同一时间从同一数据库读取数据，但只能有一个可以写入数据。

3.SQLite的使用

先写一个数据库的类

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复制代码public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "test.db";
private static final int DATABASE_VERSION = 1;
public DatabaseHelper(Context context) {
//CursorFactory设置为null,使用默认值
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
//数据库第一次被创建时onCreate会被调用
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE IF NOT EXISTS person" +
"(_id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR, age INTEGER, info TEXT)");
}
//如果DATABASE_VERSION值被改为2,系统发现现有数据库版本不同,即会调用onUpgrade
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("ALTER TABLE person ADD COLUMN other STRING");
}
}public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "test.db";
private static final int DATABASE_VERSION = 1;
public DatabaseHelper(Context context) {
//CursorFactory设置为null,使用默认值
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
//数据库第一次被创建时onCreate会被调用
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE IF NOT EXISTS person" +
"(_id INTEGER PRIMARY KEY AUTOINCREMENT, name VARCHAR, age INTEGER, info TEXT)");
}
//如果DATABASE_VERSION值被改为2,系统发现现有数据库版本不同,即会调用onUpgrade
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("ALTER TABLE person ADD COLUMN other STRING");
}
}
在然后写一个数据库的管理类，管理数据库的增删改查

复制代码

public class DbManager {
private DatabaseHelper databaseHelper;
private SQLiteDatabase db;
public DbManager(Context context) {
databaseHelper = new DatabaseHelper(context);
//因为getWritableDatabase内部调用了mContext.openOrCreateDatabase(mName, 0, mFactory);
//所以要确保context已初始化,我们可以把实例化DBManager的步骤放在Activity的onCreate里
db = databaseHelper.getWritableDatabase();
}
//添加
public void add(List<Person> persons) {
db.beginTransaction();
//开始事务
try {
for (Person person : persons) {
db.execSQL("INSERT INTO person VALUES(null, ?, ?, ?)", new Object[]{person.name, person.age, person.info});
}
db.setTransactionSuccessful();
//设置事务成功完成
} finally {
db.endTransaction();
//结束事务
}
}
//查询
public List<Person> query() {
ArrayList<Person> persons = new ArrayList<Person>();
Cursor c = queryTheCursor();
while (c.moveToNext()) {
Person person = new Person();
person._id = c.getInt(c.getColumnIndex("_id"));
person.name = c.getString(c.getColumnIndex("name"));
person.age = c.getInt(c.getColumnIndex("age"));
person.info = c.getString(c.getColumnIndex("info"));
Log.e("msg", person.name+" "+person.age+person.info);
persons.add(person);
}
c.close();
return persons;
}
public Cursor queryTheCursor() {
Cursor c = db.rawQuery("SELECT * FROM person", null);
return c;
}
//改
public void updateAge(Person person) {
ContentValues cv = new ContentValues();
cv.put("age", person.age);
cv.put("info", person.info);
db.update("person", cv, "name = ?", new String[]{person.name});
}
//删
public void deleteOldPerson(Person person) {
db.delete("person", "age >= ?", new String[]{String.valueOf(person.age)});
}
}
实体类public class Person {
public int _id;
public String name;
public int age;
public String info;
public Person() {
}
public Person(String name, int age, String info) {
this.name = name;
this.age = age;
this.info = info;
}
}

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复制代码public class DbManager {
private DatabaseHelper databaseHelper;
private SQLiteDatabase db;
public DbManager(Context context) {
databaseHelper = new DatabaseHelper(context);
//因为getWritableDatabase内部调用了mContext.openOrCreateDatabase(mName, 0, mFactory);
//所以要确保context已初始化,我们可以把实例化DBManager的步骤放在Activity的onCreate里
db = databaseHelper.getWritableDatabase();
}
//添加
public void add(List<Person> persons) {
db.beginTransaction();
//开始事务
try {
for (Person person : persons) {
db.execSQL("INSERT INTO person VALUES(null, ?, ?, ?)", new Object[]{person.name, person.age, person.info});
}
db.setTransactionSuccessful();
//设置事务成功完成
} finally {
db.endTransaction();
//结束事务
}
}
//查询
public List<Person> query() {
ArrayList<Person> persons = new ArrayList<Person>();
Cursor c = queryTheCursor();
while (c.moveToNext()) {
Person person = new Person();
person._id = c.getInt(c.getColumnIndex("_id"));
person.name = c.getString(c.getColumnIndex("name"));
person.age = c.getInt(c.getColumnIndex("age"));
person.info = c.getString(c.getColumnIndex("info"));
Log.e("msg", person.name+" "+person.age+person.info);
persons.add(person);
}
c.close();
return persons;
}
public Cursor queryTheCursor() {
Cursor c = db.rawQuery("SELECT * FROM person", null);
return c;
}
//改
public void updateAge(Person person) {
ContentValues cv = new ContentValues();
cv.put("age", person.age);
cv.put("info", person.info);
db.update("person", cv, "name = ?", new String[]{person.name});
}
//删
public void deleteOldPerson(Person person) {
db.delete("person", "age >= ?", new String[]{String.valueOf(person.age)});
}
}
实体类复制代码public class DbManager {
private DatabaseHelper databaseHelper;
private SQLiteDatabase db;
public DbManager(Context context) {
databaseHelper = new DatabaseHelper(context);
//因为getWritableDatabase内部调用了mContext.openOrCreateDatabase(mName, 0, mFactory);
//所以要确保context已初始化,我们可以把实例化DBManager的步骤放在Activity的onCreate里
db = databaseHelper.getWritableDatabase();
}
//添加
public void add(List<Person> persons) {
db.beginTransaction();
//开始事务
try {
for (Person person : persons) {
db.execSQL("INSERT INTO person VALUES(null, ?, ?, ?)", new Object[]{person.name, person.age, person.info});
}
db.setTransactionSuccessful();
//设置事务成功完成
} finally {
db.endTransaction();
//结束事务
}
}
//查询
public List<Person> query() {
ArrayList<Person> persons = new ArrayList<Person>();
Cursor c = queryTheCursor();
while (c.moveToNext()) {
Person person = new Person();
person._id = c.getInt(c.getColumnIndex("_id"));
person.name = c.getString(c.getColumnIndex("name"));
person.age = c.getInt(c.getColumnIndex("age"));
person.info = c.getString(c.getColumnIndex("info"));
Log.e("msg", person.name+" "+person.age+person.info);
persons.add(person);
}
c.close();
return persons;
}
public Cursor queryTheCursor() {
Cursor c = db.rawQuery("SELECT * FROM person", null);
return c;
}
//改
public void updateAge(Person person) {
ContentValues cv = new ContentValues();
cv.put("age", person.age);
cv.put("info", person.info);
db.update("person", cv, "name = ?", new String[]{person.name});
}
//删
public void deleteOldPerson(Person person) {
db.delete("person", "age >= ?", new String[]{String.valueOf(person.age)});
}
}
public class DbManager {
private DatabaseHelper databaseHelper;
private SQLiteDatabase db;
public DbManager(Context context) {
databaseHelper = new DatabaseHelper(context);
//因为getWritableDatabase内部调用了mContext.openOrCreateDatabase(mName, 0, mFactory);
//所以要确保context已初始化,我们可以把实例化DBManager的步骤放在Activity的onCreate里
db = databaseHelper.getWritableDatabase();
}
//添加
public void add(List<Person> persons) {
db.beginTransaction();
//开始事务
try {
for (Person person : persons) {
db.execSQL("INSERT INTO person VALUES(null, ?, ?, ?)", new Object[]{person.name, person.age, person.info});
}
db.setTransactionSuccessful();
//设置事务成功完成
} finally {
db.endTransaction();
//结束事务
}
}
//查询
public List<Person> query() {
ArrayList<Person> persons = new ArrayList<Person>();
Cursor c = queryTheCursor();
while (c.moveToNext()) {
Person person = new Person();
person._id = c.getInt(c.getColumnIndex("_id"));
person.name = c.getString(c.getColumnIndex("name"));
person.age = c.getInt(c.getColumnIndex("age"));
person.info = c.getString(c.getColumnIndex("info"));
Log.e("msg", person.name+" "+person.age+person.info);
persons.add(person);
}
c.close();
return persons;
}
public Cursor queryTheCursor() {
Cursor c = db.rawQuery("SELECT * FROM person", null);
return c;
}
//改
public void updateAge(Person person) {
ContentValues cv = new ContentValues();
cv.put("age", person.age);
cv.put("info", person.info);
db.update("person", cv, "name = ?", new String[]{person.name});
}
//删
public void deleteOldPerson(Person person) {
db.delete("person", "age >= ?", new String[]{String.valueOf(person.age)});
}
}

实体类
复制代码public class Person {
public int _id;
public String name;
public int age;
public String info;
public Person() {
}
public Person(String name, int age, String info) {
this.name = name;
this.age = age;
this.info = info;
}
}复制代码public class Person {
public int _id;
public String name;
public int age;
public String info;
public Person() {
}
public Person(String name, int age, String info) {
this.name = name;
this.age = age;
this.info = info;
}
}public class Person {
public int _id;
public String name;
public int age;
public String info;
public Person() {
}
public Person(String name, int age, String info) {
this.name = name;
this.age = age;
this.info = info;
}
}


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