android复制数据库到SD卡
android中使用sqlite、复制assets下的数据库到SD卡、支持大于1M的文件
如果使用SD卡，需要在AndroidManifest.xml中设置权限
<
uses-permission
android:name
="android.permission.WRITE_EXTERNAL_STORAGE"
></
uses-permission
>
<
uses-permission
android:name
="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"
></
uses-permission
>
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package
cn.arthur.common;
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3
import
java.io.File;
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import
java.io.FileOutputStream;
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import
java.io.IOException;
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import
java.io.InputStream;
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import
java.io.OutputStream;
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import
android.content.Context;
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import
android.database.sqlite.SQLiteDatabase;
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import
android.database.sqlite.SQLiteDatabase.CursorFactory;
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import
android.database.sqlite.SQLiteException;
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import
android.database.sqlite.SQLiteOpenHelper;
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/**
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*
@author
Joshua
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* 用法：
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* DBHelper dbHelper = new DBHelper(this);
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* dbHelper.createDataBase();
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* SQLiteDatabase db = dbHelper.getWritableDatabase();
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* Cursor cursor = db.query()
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* db.execSQL(sqlString);
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* 注意：execSQL不支持带;的多条SQL语句，只能一条一条的执行，晕了很久才明白
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* 见execSQL的源码注释 (Multiple statements separated by ;s are not supported.)
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* 将把assets下的数据库文件直接复制到DB_PATH，但数据库文件大小限制在1M以下
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* 如果有超过1M的大文件，则需要先分割为N个小文件，然后使用copyBigDatabase()替换copyDatabase()
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*/
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public
class
DBHelper
extends
SQLiteOpenHelper {
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//
用户数据库文件的版本
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private
static
final
int
DB_VERSION
=
1
;
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//
数据库文件目标存放路径为系统默认位置，cn.arthur.examples 是你的包名
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private
static
String DB_PATH
=
"
/data/data/cn.arthur.examples/databases/
"
;
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/*
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//如果你想把数据库文件存放在SD卡的话
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private static String DB_PATH = android.os.Environment.getExternalStorageDirectory().getAbsolutePath()
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+ "/arthurcn/drivertest/packfiles/";
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*/
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private
static
String DB_NAME
=
"
hello.db
"
;
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private
static
String ASSETS_NAME
=
"
hello.db
"
;
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private
SQLiteDatabase myDataBase
=
null
;
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private
final
Context myContext;
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/**
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* 如果数据库文件较大，使用FileSplit分割为小于1M的小文件
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* 此例中分割为 hello.db.101 hello.db.102 hello.db.103
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*/
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//
第一个文件名后缀
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private
static
final
int
ASSETS_SUFFIX_BEGIN
=
101
;
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//
最后一个文件名后缀
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private
static
final
int
ASSETS_SUFFIX_END
=
103
;
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/**
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* 在SQLiteOpenHelper的子类当中，必须有该构造函数
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*
@param
context 上下文对象
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*
@param
name 数据库名称
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*
@param
factory 一般都是null
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*
@param
version 当前数据库的版本，值必须是整数并且是递增的状态
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*/
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public
DBHelper(Context context, String name, CursorFactory factory,
int
version) {
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//
必须通过super调用父类当中的构造函数
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super
(context, name,
null
, version);
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this
.myContext
=
context;
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}
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public
DBHelper(Context context, String name,
int
version){
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this
(context,name,
null
,version);
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}
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public
DBHelper(Context context, String name){
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this
(context,name,DB_VERSION);
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}
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public
DBHelper (Context context) {
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this
(context, DB_PATH
+
DB_NAME);
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}
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public
void
createDataBase()
throws
IOException{
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boolean
dbExist
=
checkDataBase();
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if
(dbExist){
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//
数据库已存在，do nothing.
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}
else
{
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//
创建数据库
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try
{
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File dir
=
new
File(DB_PATH);
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if
(
!
dir.exists()){
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dir.mkdirs();
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}
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File dbf
=
new
File(DB_PATH
+
DB_NAME);
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if
(dbf.exists()){
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dbf.delete();
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}
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SQLiteDatabase.openOrCreateDatabase(dbf,
null
);
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//
复制asseets中的db文件到DB_PATH下
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copyDataBase();
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}
catch
(IOException e) {
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throw
new
Error(
"
数据库创建失败
"
);
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}
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}
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}
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//
检查数据库是否有效
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private
boolean
checkDataBase(){
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SQLiteDatabase checkDB
=
null
;
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String myPath
=
DB_PATH
+
DB_NAME;
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try
{
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checkDB
=
SQLiteDatabase.openDatabase(myPath,
null
, SQLiteDatabase.OPEN_READONLY);
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}
catch
(SQLiteException e){
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//
database does't exist yet.
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}
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if
(checkDB
!=
null
){
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checkDB.close();
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}
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return
checkDB
!=
null
?
true
:
false
;
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}
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/**
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* Copies your database from your local assets-folder to the just created empty database in the
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* system folder, from where it can be accessed and handled.
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* This is done by transfering bytestream.
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*
*/
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private
void
copyDataBase()
throws
IOException{
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//
Open your local db as the input stream
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InputStream myInput
=
myContext.getAssets().open(ASSETS_NAME);
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//
Path to the just created empty db
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String outFileName
=
DB_PATH
+
DB_NAME;
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//
Open the empty db as the output stream
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OutputStream myOutput
=
new
FileOutputStream(outFileName);
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//
transfer bytes from the inputfile to the outputfile
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byte
[] buffer
=
new
byte
[
1024
];
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int
length;
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while
((length
=
myInput.read(buffer))
>
0
){
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myOutput.write(buffer,
0
, length);
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}
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//
Close the streams
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myOutput.flush();
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myOutput.close();
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myInput.close();
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}
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//
复制assets下的大数据库文件时用这个
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private
void
copyBigDataBase()
throws
IOException{
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InputStream myInput;
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String outFileName
=
DB_PATH
+
DB_NAME;
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OutputStream myOutput
=
new
FileOutputStream(outFileName);
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for
(
int
i
=
ASSETS_SUFFIX_BEGIN; i
<
ASSETS_SUFFIX_END
+
1
; i
++
) {
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myInput
=
myContext.getAssets().open(ASSETS_NAME
+
"
.
"
+
i);
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byte
[] buffer
=
new
byte
[
1024
];
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int
length;
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while
((length
=
myInput.read(buffer))
>
0
){
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myOutput.write(buffer,
0
, length);
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}
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myOutput.flush();
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myInput.close();
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}
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myOutput.close();
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}
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@Override
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public
synchronized
void
close() {
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if
(myDataBase
!=
null
){
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myDataBase.close();
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}
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super
.close();
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}
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/**
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* 该函数是在第一次创建的时候执行，
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* 实际上是第一次得到SQLiteDatabase对象的时候才会调用这个方法
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*/
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@Override
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public
void
onCreate(SQLiteDatabase db) {
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}
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/**
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* 数据库表结构有变化时采用
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*/
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@Override
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public
void
onUpgrade(SQLiteDatabase db,
int
oldVersion,
int
newVersion) {
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}
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}
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