如何从Android的一个辅助类初始化SQLite数据库一次 [英] How to initialize sqlite database once from a helper class in Android
问题描述
我有延伸SQLiteOpenHelper,它看起来像这样一个自定义DataBaseHelper类:
包com.stampii.stampii.comm.rpc;
进口的java.io.File;
进口java.io.FileOutputStream中;
进口java.io.IOException异常;
进口的java.io.InputStream;
进口java.io.OutputStream中;
进口java.sql.ResultSet中;
进口android.content.ContentValues;
进口android.content.Context;
进口android.database.Cursor;
进口android.database.sqlite.SQLiteDatabase;
进口android.database.sqlite.SQLiteDatabase.CursorFactory;
进口android.database.sqlite.SQLiteException;
进口android.database.sqlite.SQLiteOpenHelper;
进口android.util.Log;
公共类DataBaseHelper扩展SQLiteOpenHelper {
私有静态SQLiteDatabase sqliteDb;
私有静态DataBaseHelper实例;
私有静态最终诠释DATABASE_VERSION = 1;
//默认的数据库路径是:
// /数据/数据/ pkgNameOfYourApplication /数据库/
私有静态字符串DB_PATH_ preFIX =/数据/数据/;
私有静态字符串DB_PATH_SUFFIX =/数据库/;
私有静态最后字符串变量=DataBaseHelper;
私人上下文的背景下;
/ ***
*构造器
*
* @参数方面
*:应用程序上下文
* @参数名称
*:数据库名称
* @参数厂
*:光标厂
* @参数版本
*:DB版
* /
公共DataBaseHelper(上下文的背景下,字符串名称,
CursorFactory工厂,INT版){
超(背景下,名称,厂家,版本);
this.context =背景;
Log.i(TAG,创建或打开数据库:+姓名);
}
/ ***
*初始化方法
*
* @参数方面
*:应用程序上下文
* @参数DATABASENAME
*:数据库名称
* /
公共静态无效初始化(上下文的背景下,字符串DATABASENAME){
如果(例如== NULL){
/ **
*尝试检查是否有DB的资产原件
* 目录
* /
如果(!checkDatabase(上下文,DATABASENAME)){
//如果不存在,我试着从资产目录复制
尝试 {
copyDataBase(背景下,数据库名称);
}赶上(IOException异常E){
Log.e(TAG,数据库+数据库名+并不存在,没有原始版本的资产目录);
}
}
Log.i(TAG,尝试创建数据库(实例+ DATABASENAME
+));
例如=新DataBaseHelper(背景下,数据库名称,
空,DATABASE_VERSION);
sqliteDb = instance.getWritableDatabase();
Log.i(TAG,+数据库名+数据库(实例,创建)!);
}
}
/ ***
*静态方法获取单个实例
*
* @参数方面
*:应用程序上下文
* @参数DATABASENAME
*:数据库名称
* @返回:一个实例
* /
公共静态最终DataBaseHelper的getInstance(
上下文的背景下,字符串DATABASENAME){
初始化(背景下,数据库名称);
返回实例;
}
/ ***
*方法获取数据库实例
*
* @返回数据库实例
* /
公共SQLiteDatabase getDatabase(){
返回sqliteDb;
}
@覆盖
公共无效的onCreate(SQLiteDatabase DB){
Log.d(TAG的onCreate:无关);
}
@覆盖
公共无效onUpgrade(SQLiteDatabase分贝,INT oldVersion,诠释静态网页){
Log.d(TAG,onUpgrade:无关);
}
/ ***
*法复制数据库的资产目录中应用程序的数据
* 目录
*
* @参数DATABASENAME
*:数据库名称
* @throws IOException异常
*:异常,如果文件不存在
* /
公共无效copyDataBase(字符串数据库名称)抛出IOException异常{
copyDataBase(背景下,数据库名称);
}
/ ***
*从资产目录复制数据库应用程序的静态方法
*数据目录
*
* @参数aContext
*:应用程序上下文
* @参数DATABASENAME
*:数据库名称
* @throws IOException异常
*:异常,如果文件不存在
* /
私有静态无效copyDataBase(上下文aContext,串DATABASENAME)
抛出IOException异常{
//打开本地数据库作为输入流
InputStream的myInput = aContext.getAssets()开(数据库名称)。
//路径刚刚创建的空分贝
字符串outFileName = getDatabasePath(aContext,数据库名称);
Log.i(TAG,检查创建目录:+ DB_PATH_ preFIX
+ aContext.getPackageName()+ DB_PATH_SUFFIX);
//如果路径不首先存在,创建它
文件F =新的文件(DB_PATH_ preFIX + aContext.getPackageName()
+ DB_PATH_SUFFIX);
如果(!f.exists())
f.mkdir();
Log.i(TAG,试图本地数据库复制到:+ outFileName);
//打开空分贝的输出流
的OutputStream myOutput =新的FileOutputStream(outFileName);
//传输的字节从inputfile中的OUTPUTFILE
byte []的缓冲区=新的字节[1024];
INT长;
而((长度= myInput.read(缓冲液))大于0){
myOutput.write(缓冲液,0,长度);
}
//关闭流
myOutput.flush();
myOutput.close();
myInput.close();
Log.i(TAG,DB(+数据库名称+)复制!);
}
/ ***
*方法来检查是否数据库存在于应用程序的数据目录
*
* @参数DATABASENAME
*:数据库名称
* @返回:布尔(true如果存在的话)
* /
公共布尔checkDatabase(字符串DATABASENAME){
返回checkDatabase(背景下,数据库名称);
}
/ ***
*静态方法来检查,如果数据库存在于应用程序的数据目录
*
* @参数aContext
*:应用程序上下文
* @参数DATABASENAME
*:数据库名称
* @返回:布尔(true如果存在的话)
* /
私有静态布尔checkDatabase(上下文aContext,串DATABASENAME){
SQLiteDatabase CHECKDB = NULL;
尝试 {
字符串mypath中= getDatabasePath(aContext,数据库名称);
Log.i(TAG,试图conntect为:+ mypath中);
CHECKDB = SQLiteDatabase.openDatabase(mypath中,空,
SQLiteDatabase.OPEN_READONLY);
Log.i(TAG,数据库+数据库名+找到了!);
checkDB.close();
}赶上(SQLiteException E){
Log.i(TAG,数据库+数据库名+不存在!);
}
返回CHECKDB!= NULL?真假;
}
/ ***
*方法返回数据库路径在应用程序的数据目录
*
* @参数DATABASENAME
*:数据库名称
* @返回:完整路径
* /
私人字符串getDatabasePath(最后弦乐DATABASENAME){
返回getDatabasePath(背景下,数据库名称);
}
/ ***
*静态方法返回数据库路径中的应用程序的数据
* 目录
*
* @参数aContext
*:应用程序上下文
* @参数DATABASENAME
*:数据库名称
* @返回:完整路径
* /
私有静态字符串getDatabasePath(上下文aContext,串DATABASENAME){
返回DB_PATH_ preFIX + aContext.getPackageName()+ DB_PATH_SUFFIX
+ DATABASENAME;
}
公共布尔的executeQuery(字符串tableName值,字符串键,字符串值){
返回的ExecQuery(tableName值,键,值);
}
私有静态布尔的ExecQuery(字符串tableName值,字符串键,字符串值){
sqliteDb = instance.getWritableDatabase();
ContentValues值=新ContentValues();
values.put(键,值);
sqliteDb.insert(tableName值,空,价值观);
返回true;
}
公共布尔即updateSQL(字符串tableName值,字符串键,字符串值){
返回了updateData(tableName值,键,值);
}
私有静态布尔了updateData(字符串tableName值,字符串键,字符串值){
sqliteDb = instance.getWritableDatabase();
字符串,其中=code_ID =?;
ContentValues值=新ContentValues();
values.put(键,值);
values.put(键,值);
sqliteDb.update(tableName值,值,其中,新的String [] {3});
返回true;
}
公共布尔deleteSQL(字符串tableName值){
返回deleteData(tableName值);
}
私有静态布尔deleteData(字符串tableName值){
sqliteDb = instance.getWritableDatabase();
字符串,其中=code_ID =?;
sqliteDb.delete(tableName值,其中,新的String [] {5});
返回true;
}
公共光标executeSQLQuery(查询字符串){
返回sqliteDb.rawQuery(查询,NULL);
}
}
我的问题是:我怎么能初始化数据库只有一次,可以从我的所有活动的机会呢? (提示:我在资产的文件夹,我复制到我的系统数据库文件夹有sqlite的文件时,应用程序星级)
在此先感谢!
编辑:我忘了说,我在我的应用2种不同的SQLite数据库,我希望能够初始化二者为整个应用程序,并可以使用了进来的东西,我试图做的:
DataBaseHelper dbHelper;
//一些code
dbHelper =新DataBaseHelper(上下文中,ops_sys_tpl.sqlite,空,1);
DataBaseHelper.initialize(上下文中,stampii_sys_tpl.sqlite);
dbHelper.copyDataBase(ops_sys_tpl.sqlite);
dbHelper.getDatabase();
dbHelper.executeQuery(用户,的ObjectID,2);
dbHelper.executeQuery(用户,的serverName,stampii);
dbHelper.executeQuery(用户,的ObjectID,3);
dbHelper.executeQuery(用户,的serverName,stampii);
dbHelper.executeQuery(用户,的ObjectID,3);
创建您的实例只有一次这样,同code,你可以添加在数据库处理程序类,但我preFER以保持其独立的。
公共类MyTestDatabaseInstanceHolder {
公共MyTestDBHandler DBHelper;
公共静态SQLiteDatabase m_ObjDataBase; //这是跨应用程序了访问全局变量
公共静态无效createDBInstance(上下文pContext){
如果(DBHelper == NULL){
DBHelper =新WLDBHandler(pContext); //这将是你的数据库处理类
m_cObjDataBase = DBHelper.openAndCreateDataBase(); // Initialze数据库注:openAndCreateDataBase是您创建做的一切的回报数据库对象的实用方法
}
}
}
在您的入口点(闪屏)称这样的:
MyTestDatabaseInstanceHolder.createDBInstance(getApplicationContext());
用法 - 一些其他类:
MyTestDatabaseInstanceHolder.m_ObjDataBase.rawQuery( - );
I have a custom DataBaseHelper class which extends SQLiteOpenHelper,which looks like this :
package com.stampii.stampii.comm.rpc;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.sql.ResultSet;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DataBaseHelper extends SQLiteOpenHelper{
private static SQLiteDatabase sqliteDb;
private static DataBaseHelper instance;
private static final int DATABASE_VERSION = 1;
// the default database path is :
// /data/data/pkgNameOfYourApplication/databases/
private static String DB_PATH_PREFIX = "/data/data/";
private static String DB_PATH_SUFFIX = "/databases/";
private static final String TAG = "DataBaseHelper";
private Context context;
/***
* Contructor
*
* @param context
* : app context
* @param name
* : database name
* @param factory
* : cursor Factory
* @param version
* : DB version
*/
public DataBaseHelper(Context context, String name,
CursorFactory factory, int version) {
super(context, name, factory, version);
this.context = context;
Log.i(TAG, "Create or Open database : " + name);
}
/***
* Initialize method
*
* @param context
* : application context
* @param databaseName
* : database name
*/
public static void initialize(Context context, String databaseName) {
if (instance == null) {
/**
* Try to check if there is an Original copy of DB in asset
* Directory
*/
if (!checkDatabase(context, databaseName)) {
// if not exists, I try to copy from asset dir
try {
copyDataBase(context, databaseName);
} catch (IOException e) {
Log.e(TAG,"Database "+ databaseName+" does not exists and there is no Original Version in Asset dir");
}
}
Log.i(TAG, "Try to create instance of database (" + databaseName
+ ")");
instance = new DataBaseHelper(context, databaseName,
null, DATABASE_VERSION);
sqliteDb = instance.getWritableDatabase();
Log.i(TAG, "instance of database (" + databaseName + ") created !");
}
}
/***
* Static method for getting singleton instance
*
* @param context
* : application context
* @param databaseName
* : database name
* @return : singleton instance
*/
public static final DataBaseHelper getInstance(
Context context, String databaseName) {
initialize(context, databaseName);
return instance;
}
/***
* Method to get database instance
*
* @return database instance
*/
public SQLiteDatabase getDatabase() {
return sqliteDb;
}
@Override
public void onCreate(SQLiteDatabase db) {
Log.d(TAG, "onCreate : nothing to do");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
Log.d(TAG, "onUpgrade : nothing to do");
}
/***
* Method for Copy the database from asset directory to application's data
* directory
*
* @param databaseName
* : database name
* @throws IOException
* : exception if file does not exists
*/
public void copyDataBase(String databaseName) throws IOException {
copyDataBase(context, databaseName);
}
/***
* Static method for copy the database from asset directory to application's
* data directory
*
* @param aContext
* : application context
* @param databaseName
* : database name
* @throws IOException
* : exception if file does not exists
*/
private static void copyDataBase(Context aContext, String databaseName)
throws IOException {
// Open your local db as the input stream
InputStream myInput = aContext.getAssets().open(databaseName);
// Path to the just created empty db
String outFileName = getDatabasePath(aContext, databaseName);
Log.i(TAG, "Check if create dir : " + DB_PATH_PREFIX
+ aContext.getPackageName() + DB_PATH_SUFFIX);
// if the path doesn't exist first, create it
File f = new File(DB_PATH_PREFIX + aContext.getPackageName()
+ DB_PATH_SUFFIX);
if (!f.exists())
f.mkdir();
Log.i(TAG, "Trying to copy local DB to : " + outFileName);
// Open the empty db as the output stream
OutputStream myOutput = new FileOutputStream(outFileName);
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
Log.i(TAG, "DB (" + databaseName + ") copied!");
}
/***
* Method to check if database exists in application's data directory
*
* @param databaseName
* : database name
* @return : boolean (true if exists)
*/
public boolean checkDatabase(String databaseName) {
return checkDatabase(context, databaseName);
}
/***
* Static Method to check if database exists in application's data directory
*
* @param aContext
* : application context
* @param databaseName
* : database name
* @return : boolean (true if exists)
*/
private static boolean checkDatabase(Context aContext, String databaseName) {
SQLiteDatabase checkDB = null;
try {
String myPath = getDatabasePath(aContext, databaseName);
Log.i(TAG, "Trying to conntect to : " + myPath);
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
Log.i(TAG, "Database " + databaseName + " found!");
checkDB.close();
} catch (SQLiteException e) {
Log.i(TAG, "Database " + databaseName + " does not exists!");
}
return checkDB != null ? true : false;
}
/***
* Method that returns database path in the application's data directory
*
* @param databaseName
* : database name
* @return : complete path
*/
private String getDatabasePath(final String databaseName) {
return getDatabasePath(context, databaseName);
}
/***
* Static Method that returns database path in the application's data
* directory
*
* @param aContext
* : application context
* @param databaseName
* : database name
* @return : complete path
*/
private static String getDatabasePath(Context aContext, String databaseName) {
return DB_PATH_PREFIX + aContext.getPackageName() + DB_PATH_SUFFIX
+ databaseName;
}
public boolean executeQuery(String tableName,String keys,String value){
return execQuery(tableName,keys,value);
}
private static boolean execQuery(String tableName,String key,String value){
sqliteDb = instance.getWritableDatabase();
ContentValues values = new ContentValues();
values.put(key, value);
sqliteDb.insert(tableName, null, values);
return true;
}
public boolean updateSQL(String tableName,String key,String value){
return updateData(tableName,key,value);
}
private static boolean updateData(String tableName,String key,String value){
sqliteDb = instance.getWritableDatabase();
String where = "code_id=?";
ContentValues values = new ContentValues();
values.put(key, value);
values.put(key, value);
sqliteDb.update(tableName, values, where, new String[] {"3"});
return true;
}
public boolean deleteSQL(String tableName){
return deleteData(tableName);
}
private static boolean deleteData(String tableName){
sqliteDb = instance.getWritableDatabase();
String where = "code_id=?";
sqliteDb.delete(tableName, where, new String[] {"5"});
return true;
}
public Cursor executeSQLQuery(String query){
return sqliteDb.rawQuery(query,null);
}
}
My question is : How can I initialize the database only once and can access it from all my Activities? (Hint: I have sqlite files in my assets folder,which I copy to my system database folder when the app stars.)
Thanks in advance!
EDIT : I forgot to say that I have 2 different sqlite databases in my application and I want to be able to initialize both of them for the whole application and can use them.That's something that I was trying to do :
DataBaseHelper dbHelper;
//some code
dbHelper = new DataBaseHelper(context, "ops_sys_tpl.sqlite", null, 1);
DataBaseHelper.initialize(context, "stampii_sys_tpl.sqlite");
dbHelper.copyDataBase("ops_sys_tpl.sqlite");
dbHelper.getDatabase();
dbHelper.executeQuery("users", "objectId", "2");
dbHelper.executeQuery("users","serverName","stampii");
dbHelper.executeQuery("users", "objectId", "3");
dbHelper.executeQuery("users","serverName","stampii");
dbHelper.executeQuery("users", "objectId", "3");
Create your instance only once like this, The same code you can add in DB handler class but I prefer to keep it seperate.
public class MyTestDatabaseInstanceHolder {
public MyTestDBHandler DBHelper;
public static SQLiteDatabase m_ObjDataBase; // This is global variable to access across the applicaiton
public static void createDBInstance(Context pContext){
if(DBHelper == null) {
DBHelper = new WLDBHandler(pContext); // This will be your DB Handler Class
m_cObjDataBase = DBHelper.openAndCreateDataBase(); // Initialze the DB Note: openAndCreateDataBase is a utility method created by you to do everything an return the DB object
}
}
}
In your entry point (Splash Screen) call this:
MyTestDatabaseInstanceHolder.createDBInstance(getApplicationContext());
Usage - Some other Class:
MyTestDatabaseInstanceHolder.m_ObjDataBase.rawQuery(---);
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