【移動應(yīng)用開發(fā)技術(shù)】Android中怎么升級SQLite數(shù)據(jù)庫版本

【移動應(yīng)用開發(fā)技術(shù)】Android中怎么升級SQLite數(shù)據(jù)庫版本

這篇文章給大家介紹Android中怎么升級SQLite數(shù)據(jù)庫版本，內(nèi)容非常詳細(xì)，感興趣的小伙伴們可以參考借鑒，希望對大家能有所幫助。AndroidSQLite數(shù)據(jù)庫版本升級的管理實(shí)現(xiàn)我們知道在SQLiteOpenHelper的構(gòu)造方法:super(Context

context,

String

name,

SQLiteDatabase.CursorFactory

factory,

int

version)中最后一個參數(shù)表示數(shù)據(jù)庫的版本號.當(dāng)新的版本號大于當(dāng)前的version時會調(diào)用方法:onUpgrade(SQLiteDatabase

db,

int

oldVersion,

int

newVersion)所以我們的重點(diǎn)是在該方法中實(shí)現(xiàn)SQLite數(shù)據(jù)庫版本升級的管理當(dāng)我們項(xiàng)目剛開始的時候第一版SQLiteOpenHelper是這樣寫的:package

cc.database;

import

android.content.Context;

import

android.database.sqlite.SQLiteDatabase;

import

android.database.sqlite.SQLiteDatabase.CursorFactory;

import

android.database.sqlite.SQLiteOpenHelper;

/**

*

Demo描述:

*

SQLite數(shù)據(jù)庫版本升級的管理實(shí)現(xiàn)

*

*

參考資料:

*

/guolin_blog

*

Thank

you

very

much

*/

public

class

DataBaseOpenHelper

extends

SQLiteOpenHelper

{

private

final

static

String

DATABASE_NAME="test.db";

private

static

DataBaseOpenHelper

mDataBaseOpenHelper;

public

static

final

String

CREATE_PERSON=

"create

table

person(personid

integer

primary

key

autoincrement,name

varchar(20),phone

VARCHAR(12))";

public

DataBaseOpenHelper(Context

context,String

name,CursorFactory

factory,int

version)

{

super(context,

name,

factory,

version);

}

//注意:

//將DataBaseOpenHelper寫成單例的.

//否則當(dāng)在一個for循環(huán)中頻繁調(diào)用openHelper.getWritableDatabase()時

//會報錯,提示數(shù)據(jù)庫沒有執(zhí)行關(guān)閉操作

static

synchronized

DataBaseOpenHelper

getDBInstance(Context

context)

{

if

(mDataBaseOpenHelper

==

null)

{

mDataBaseOpenHelper

=

new

DataBaseOpenHelper(context,DATABASE_NAME,null,1);

}

return

mDataBaseOpenHelper;

}

@Override

public

void

onCreate(SQLiteDatabase

db)

{

db.execSQL(CREATE_PERSON);

}

@Override

public

void

onUpgrade(SQLiteDatabase

db,

int

oldVersion,

int

newVersion)

{

}

}在幾天之后根據(jù)項(xiàng)目需求，需要添加一張student表，于是DataBaseOpenHelper就出現(xiàn)了第二版:package

cc.database;

import

android.content.Context;

import

android.database.sqlite.SQLiteDatabase;

import

android.database.sqlite.SQLiteDatabase.CursorFactory;

import

android.database.sqlite.SQLiteOpenHelper;

public

class

DataBaseOpenHelper

extends

SQLiteOpenHelper

{

private

final

static

String

DATABASE_NAME="test.db";

private

static

DataBaseOpenHelper

mDataBaseOpenHelper;

public

static

final

String

CREATE_PERSON=

"create

table

person(personid

integer

primary

key

autoincrement,name

varchar(20),phone

VARCHAR(12))";

public

static

final

String

CREATE_STUDENT=

"create

table

student(studentid

integer

primary

key

autoincrement,name

varchar(20),phone

VARCHAR(12))";

public

DataBaseOpenHelper(Context

context,String

name,CursorFactory

factory,int

version)

{

super(context,

name,

factory,

version);

}

//注意:

//將DataBaseOpenHelper寫成單例的.

//否則當(dāng)在一個for循環(huán)中頻繁調(diào)用openHelper.getWritableDatabase()時

//會報錯,提示數(shù)據(jù)庫沒有執(zhí)行關(guān)閉操作

static

synchronized

DataBaseOpenHelper

getDBInstance(Context

context)

{

if

(mDataBaseOpenHelper

==

null)

{

//改動1

mDataBaseOpenHelper

=

new

DataBaseOpenHelper(context,DATABASE_NAME,null,2);

}

return

mDataBaseOpenHelper;

}

@Override

public

void

onCreate(SQLiteDatabase

db)

{

db.execSQL(CREATE_PERSON);

//改動2

db.execSQL(CREATE_STUDENT);

}

@Override

public

void

onUpgrade(SQLiteDatabase

db,

int

oldVersion,

int

newVersion)

{

//改動3

switch

(oldVersion)

{

case

1:

db.execSQL(CREATE_STUDENT);

default:

}

}

}較版本一在版本二中有三處修改的地方：1版本號變成了22在onCreate()方法中添加了代碼db.execSQL(CREATE_STUDENT);創(chuàng)建student表

因?yàn)橛械挠脩舾揪蜎]有第一版本的APP，直接從市場下載了第二版本的App。所以當(dāng)然會執(zhí)行onCreate()而不會執(zhí)行onUpgrade()3在onUpgrade()做了處理：當(dāng)oldVersion為1時調(diào)用db.execSQL(CREATE_STUDENT);創(chuàng)建student表

因?yàn)橛械挠脩羰謾C(jī)上本來就有第一版本的APP，所以在App升級到第二版本時會執(zhí)行onUpgrade()，不會執(zhí)行onCreate()通過這樣的處理使得不同的情況下使用第二版APP時都會生成student表又過了一個月，根據(jù)項(xiàng)目變更，需要給person表添加一個字段genderid，于是DataBaseOpenHelper就出現(xiàn)了第三版:package

cc.database;

import

android.content.Context;

import

android.database.sqlite.SQLiteDatabase;

import

android.database.sqlite.SQLiteDatabase.CursorFactory;

import

android.database.sqlite.SQLiteOpenHelper;

public

class

DataBaseOpenHelper

extends

SQLiteOpenHelper

{

private

final

static

String

DATABASE_NAME="test.db";

private

static

DataBaseOpenHelper

mDataBaseOpenHelper;

//改動1

public

static

final

String

CREATE_PERSON=

"create

table

person(personid

integer

primary

key

autoincrement,name

varchar(20),phone

VARCHAR(12)),genderid

integer)";

public

static

final

String

ALTER_PERSON="alter

table

person

add

column

genderid

integer";

public

static

final

String

CREATE_STUDENT=

"create

table

student(studentid

integer

primary

key

autoincrement,name

varchar(20),phone

VARCHAR(12))";

public

DataBaseOpenHelper(Context

context,String

name,CursorFactory

factory,int

version)

{

super(context,

name,

factory,

version);

}

//注意:

//將DataBaseOpenHelper寫成單例的.

//否則當(dāng)在一個for循環(huán)中頻繁調(diào)用openHelper.getWritableDatabase()時

//會報錯,提示數(shù)據(jù)庫沒有執(zhí)行關(guān)閉操作

static

synchronized

DataBaseOpenHelper

getDBInstance(Context

context)

{

if

(mDataBaseOpenHelper

==

null)

{

//改動2

mDataBaseOpenHelper

=

new

DataBaseOpenHelper(context,DATABASE_NAME,null,3);

}

return

mDataBaseOpenHelper;

}

@Override

public

void

onCreate(SQLiteDatabase

db)

{

db.execSQL(CREATE_PERSON);

db.execSQL(CREATE_STUDENT);

}

@Override

public

void

onUpgrade(SQLiteDatabase

db,

int

oldVersion,

int

newVersion)

{

switch

(oldVersion)

{

case

1:

db.execSQL(CREATE_STUDENT);