发送带有数据库的应用程序 [英] Ship an application with a database
问题描述
如果您的应用程序需要一个数据库并且它带有内置数据，那么发布该应用程序的最佳方式是什么?我应该:
If your application requires a database and it comes with built in data, what is the best way to ship that application? Should I:
预先创建 SQLite 数据库并将其包含在
.apk中?
在应用程序中包含 SQL 命令并让它创建数据库并在第一次使用时插入数据?
Include the SQL commands with the application and have it create the database and insert the data on first use?
我看到的缺点是:
可能的 SQLite 版本不匹配可能会导致问题，我目前不知道该数据库应该去哪里以及如何访问它.
Possible SQLite version mismatches might cause problems and I currently don't know where the database should go and how to access it.
在设备上创建和填充数据库可能需要很长时间.
It may take a really long time to create and populate the database on the device.
有什么建议吗?将不胜感激指向有关任何问题的文档.
Any suggestions? Pointers to the documentation regarding any issues would be greatly appreciated.
推荐答案
创建和更新数据库有两个选项.
一种是在外部创建一个数据库，然后放到项目的assets文件夹中，然后从那里复制整个数据库.如果数据库有很多表和其他组件，这会快得多.通过更改 res/values/strings.xml 文件中的数据库版本号触发升级. 然后通过在外部创建新数据库替换旧数据库来完成升级在带有新数据库的assets文件夹中，将旧数据库以另一个名称保存在内部存储中，将新数据库从assets文件夹复制到内部存储中，将旧数据库(较早重命名)中的所有数据转移到新数据库中数据库，最后删除旧数据库.您可以使用SQLite Manager FireFox 插件来创建数据库，以执行您的创建sql语句.
One is to create a database externally, then place it in the assets folder of the project and then copy the entire database from there. This is much quicker if the database has a lot of tables and other components. Upgrades are triggered by changing the database version number in the res/values/strings.xml file. Upgrades would then be accomplished by creating a new database externally, replacing the old database in the assets folder with the new database, saving the old database in internal storage under another name, copying the new database from the assets folder into internal storage, transferring all of the data from the old database (that was renamed earlier) into the new database and finally deleting the old database. You can create a database originally by using the SQLite Manager FireFox plugin to execute your creation sql statements.
另一种选择是从 sql 文件内部创建一个数据库.这不是那么快，但如果数据库只有几张表，则用户可能不会注意到延迟.通过更改 res/values/strings.xml 文件中的数据库版本号触发升级. 然后通过处理升级 sql 文件来完成升级.数据库中的数据将保持不变，除非它的容器被移除，例如删除一个表.
The other option is to create a database internally from a sql file. This is not as quick but the delay would probably be unnoticeable to the users if the database has only a few tables. Upgrades are triggered by changing the database version number in the res/values/strings.xml file. Upgrades would then be accomplished by processing an upgrade sql file. The data in the database will remain unchanged except when its container is removed, for example dropping a table.
以下示例演示了如何使用任一方法.
这是一个示例 create_database.sql 文件.内部方法要放在项目的assets文件夹中，或者复制到SQLite Manager的执行SQL"中，为外部方法创建数据库.(注意:注意注释Android 需要的表.)
Here is a sample create_database.sql file. It is to be placed in the assets folder of the project for the internal method or copied into the "Execute SQL' of SQLite Manager to create the database for the external method. (NOTE: Notice the comment about the table required by Android.)
--Android requires a table named 'android_metadata' with a 'locale' column
CREATE TABLE "android_metadata" ("locale" TEXT DEFAULT 'en_US');
INSERT INTO "android_metadata" VALUES ('en_US');
CREATE TABLE "kitchen_table";
CREATE TABLE "coffee_table";
CREATE TABLE "pool_table";
CREATE TABLE "dining_room_table";
CREATE TABLE "card_table";
这是一个示例 update_database.sql 文件.内部方法要放在项目的assets文件夹中，或者复制到SQLite Manager的执行SQL"中，为外部方法创建数据库.(注意:三种类型都可以的 SQL 注释将被包含在此示例中的 sql 解析器忽略.)
Here is a sample update_database.sql file. It is to be placed in the assets folder of the project for the internal method or copied into the "Execute SQL' of SQLite Manager to create the database for the external method. (NOTE: Notice that all three types of SQL comments will be ignored by the sql parser that is included in this example.)
--CREATE TABLE "kitchen_table"; This is one type of comment in sql. It is ignored by parseSql.
/*
* CREATE TABLE "coffee_table"; This is a second type of comment in sql. It is ignored by parseSql.
*/
{
CREATE TABLE "pool_table"; This is a third type of comment in sql. It is ignored by parseSql.
}
/* CREATE TABLE "dining_room_table"; This is a second type of comment in sql. It is ignored by parseSql. */
{ CREATE TABLE "card_table"; This is a third type of comment in sql. It is ignored by parseSql. }
--DROP TABLE "picnic_table"; Uncomment this if picnic table was previously created and now is being replaced.
CREATE TABLE "picnic_table" ("plates" TEXT);
INSERT INTO "picnic_table" VALUES ('paper');
这是要添加到/res/values/strings.xml 文件中的数据库版本号条目.
Here is an entry to add to the /res/values/strings.xml file for the database version number.
<item type="string" name="databaseVersion" format="integer">1</item>
这是一个访问数据库然后使用它的活动.(注意:如果数据库代码使用大量资源，您可能希望在单独的线程中运行该代码.)
Here is an activity that accesses the database and then uses it. (Note: You might want to run the database code in a separate thread if it uses a lot of resources.)
package android.example;
import android.app.Activity;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
/**
* @author Danny Remington - MacroSolve
*
* Activity for demonstrating how to use a sqlite database.
*/
public class Database extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
DatabaseHelper myDbHelper;
SQLiteDatabase myDb = null;
myDbHelper = new DatabaseHelper(this);
/*
* Database must be initialized before it can be used. This will ensure
* that the database exists and is the current version.
*/
myDbHelper.initializeDataBase();
try {
// A reference to the database can be obtained after initialization.
myDb = myDbHelper.getWritableDatabase();
/*
* Place code to use database here.
*/
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
myDbHelper.close();
} catch (Exception ex) {
ex.printStackTrace();
} finally {
myDb.close();
}
}
}
}
这里是数据库助手类，必要时在其中创建或更新数据库.(注意:Android 要求您创建一个扩展 SQLiteOpenHelper 的类才能使用 Sqlite 数据库.)
Here is the database helper class where the database is created or updated if necessary. (NOTE: Android requires that you create a class that extends SQLiteOpenHelper in order to work with a Sqlite database.)
package android.example;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
/**
* @author Danny Remington - MacroSolve
*
* Helper class for sqlite database.
*/
public class DatabaseHelper extends SQLiteOpenHelper {
/*
* The Android's default system path of the application database in internal
* storage. The package of the application is part of the path of the
* directory.
*/
private static String DB_DIR = "/data/data/android.example/databases/";
private static String DB_NAME = "database.sqlite";
private static String DB_PATH = DB_DIR + DB_NAME;
private static String OLD_DB_PATH = DB_DIR + "old_" + DB_NAME;
private final Context myContext;
private boolean createDatabase = false;
private boolean upgradeDatabase = false;
/**
* Constructor Takes and keeps a reference of the passed context in order to
* access to the application assets and resources.
*
* @param context
*/
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, context.getResources().getInteger(
R.string.databaseVersion));
myContext = context;
// Get the path of the database that is based on the context.
DB_PATH = myContext.getDatabasePath(DB_NAME).getAbsolutePath();
}
/**
* Upgrade the database in internal storage if it exists but is not current.
* Create a new empty database in internal storage if it does not exist.
*/
public void initializeDataBase() {
/*
* Creates or updates the database in internal storage if it is needed
* before opening the database. In all cases opening the database copies
* the database in internal storage to the cache.
*/
getWritableDatabase();
if (createDatabase) {
/*
* If the database is created by the copy method, then the creation
* code needs to go here. This method consists of copying the new
* database from assets into internal storage and then caching it.
*/
try {
/*
* Write over the empty data that was created in internal
* storage with the one in assets and then cache it.
*/
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
} else if (upgradeDatabase) {
/*
* If the database is upgraded by the copy and reload method, then
* the upgrade code needs to go here. This method consists of
* renaming the old database in internal storage, create an empty
* new database in internal storage, copying the database from
* assets to the new database in internal storage, caching the new
* database from internal storage, loading the data from the old
* database into the new database in the cache and then deleting the
* old database from internal storage.
*/
try {
FileHelper.copyFile(DB_PATH, OLD_DB_PATH);
copyDataBase();
SQLiteDatabase old_db = SQLiteDatabase.openDatabase(OLD_DB_PATH, null, SQLiteDatabase.OPEN_READWRITE);
SQLiteDatabase new_db = SQLiteDatabase.openDatabase(DB_PATH,null, SQLiteDatabase.OPEN_READWRITE);
/*
* Add code to load data into the new database from the old
* database and then delete the old database from internal
* storage after all data has been transferred.
*/
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* Copies your database from your local assets-folder to the just created
* empty database in the system folder, from where it can be accessed and
* handled. This is done by transfering bytestream.
* */
private void copyDataBase() throws IOException {
/*
* Close SQLiteOpenHelper so it will commit the created empty database
* to internal storage.
*/
close();
/*
* Open the database in the assets folder as the input stream.
*/
InputStream myInput = myContext.getAssets().open(DB_NAME);
/*
* Open the empty db in interal storage as the output stream.
*/
OutputStream myOutput = new FileOutputStream(DB_PATH);
/*
* Copy over the empty db in internal storage with the database in the
* assets folder.
*/
FileHelper.copyFile(myInput, myOutput);
/*
* Access the copied database so SQLiteHelper will cache it and mark it
* as created.
*/
getWritableDatabase().close();
}
/*
* This is where the creation of tables and the initial population of the
* tables should happen, if a database is being created from scratch instead
* of being copied from the application package assets. Copying a database
* from the application package assets to internal storage inside this
* method will result in a corrupted database.
* <P>
* NOTE: This method is normally only called when a database has not already
* been created. When the database has been copied, then this method is
* called the first time a reference to the database is retrieved after the
* database is copied since the database last cached by SQLiteOpenHelper is
* different than the database in internal storage.
*/
@Override
public void onCreate(SQLiteDatabase db) {
/*
* Signal that a new database needs to be copied. The copy process must
* be performed after the database in the cache has been closed causing
* it to be committed to internal storage. Otherwise the database in
* internal storage will not have the same creation timestamp as the one
* in the cache causing the database in internal storage to be marked as
* corrupted.
*/
createDatabase = true;
/*
* This will create by reading a sql file and executing the commands in
* it.
*/
// try {
// InputStream is = myContext.getResources().getAssets().open(
// "create_database.sql");
//
// String[] statements = FileHelper.parseSqlFile(is);
//
// for (String statement : statements) {
// db.execSQL(statement);
// }
// } catch (Exception ex) {
// ex.printStackTrace();
// }
}
/**
* Called only if version number was changed and the database has already
* been created. Copying a database from the application package assets to
* the internal data system inside this method will result in a corrupted
* database in the internal data system.
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
/*
* Signal that the database needs to be upgraded for the copy method of
* creation. The copy process must be performed after the database has
* been opened or the database will be corrupted.
*/
upgradeDatabase = true;
/*
* Code to update the database via execution of sql statements goes
* here.
*/
/*
* This will upgrade by reading a sql file and executing the commands in
* it.
*/
// try {
// InputStream is = myContext.getResources().getAssets().open(
// "upgrade_database.sql");
//
// String[] statements = FileHelper.parseSqlFile(is);
//
// for (String statement : statements) {
// db.execSQL(statement);
// }
// } catch (Exception ex) {
// ex.printStackTrace();
// }
}
/**
* Called everytime the database is opened by getReadableDatabase or
* getWritableDatabase. This is called after onCreate or onUpgrade is
* called.
*/
@Override
public void onOpen(SQLiteDatabase db) {
super.onOpen(db);
}
/*
* Add your public helper methods to access and get content from the
* database. You could return cursors by doing
* "return myDataBase.query(....)" so it'd be easy to you to create adapters
* for your views.
*/
}
这里是 FileHelper 类，它包含字节流复制文件和解析 sql 文件的方法.
Here's the FileHelper class that contains methods for byte stream copying files and parsing sql files.
package android.example;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.nio.channels.FileChannel;
/**
* @author Danny Remington - MacroSolve
*
* Helper class for common tasks using files.
*
*/
public class FileHelper {
/**
* Creates the specified <i><b>toFile</b></i> that is a byte for byte a copy
* of <i><b>fromFile</b></i>. If <i><b>toFile</b></i> already existed, then
* it will be replaced with a copy of <i><b>fromFile</b></i>. The name and
* path of <i><b>toFile</b></i> will be that of <i><b>toFile</b></i>. Both
* <i><b>fromFile</b></i> and <i><b>toFile</b></i> will be closed by this
* operation.
*
* @param fromFile
* - InputStream for the file to copy from.
* @param toFile
* - InputStream for the file to copy to.
*/
public static void copyFile(InputStream fromFile, OutputStream toFile) throws IOException {
// transfer bytes from the inputfile to the outputfile
byte[] buffer = new byte[1024];
int length;
try {
while ((length = fromFile.read(buffer)) > 0) {
toFile.write(buffer, 0, length);
}
}
// Close the streams
finally {
try {
if (toFile != null) {
try {
toFile.flush();
} finally {
toFile.close();
}
}
} finally {
if (fromFile != null) {
fromFile.close();
}
}
}
}
/**
* Creates the specified <i><b>toFile</b></i> that is a byte for byte a copy
* of <i><b>fromFile</b></i>. If <i><b>toFile</b></i> already existed, then
* it will be replaced with a copy of <i><b>fromFile</b></i>. The name and
* path of <i><b>toFile</b></i> will be that of <i><b>toFile</b></i>. Both
* <i><b>fromFile</b></i> and <i><b>toFile</b></i> will be closed by this
* operation.
*
* @param fromFile
* - String specifying the path of the file to copy from.
* @param toFile
* - String specifying the path of the file to copy to.
*/
public static void copyFile(String fromFile, String toFile) throws IOException {
copyFile(new FileInputStream(fromFile), new FileOutputStream(toFile));
}
/**
* Creates the specified <i><b>toFile</b></i> that is a byte for byte a copy
* of <i><b>fromFile</b></i>. If <i><b>toFile</b></i> already existed, then
* it will be replaced with a copy of <i><b>fromFile</b></i>. The name and
* path of <i><b>toFile</b></i> will be that of <i><b>toFile</b></i>. Both
* <i><b>fromFile</b></i> and <i><b>toFile</b></i> will be closed by this
* operation.
*
* @param fromFile
* - File for the file to copy from.
* @param toFile
* - File for the file to copy to.
*/
public static void copyFile(File fromFile, File toFile) throws IOException {
copyFile(new FileInputStream(fromFile), new FileOutputStream(toFile));
}
/**
* Creates the specified <i><b>toFile</b></i> that is a byte for byte a copy
* of <i><b>fromFile</b></i>. If <i><b>toFile</b></i> already existed, then
* it will be replaced with a copy of <i><b>fromFile</b></i>. The name and
* path of <i><b>toFile</b></i> will be that of <i><b>toFile</b></i>. Both
* <i><b>fromFile</b></i> and <i><b>toFile</b></i> will be closed by this
* operation.
*
* @param fromFile
* - FileInputStream for the file to copy from.
* @param toFile
* - FileInputStream for the file to copy to.
*/
public static void copyFile(FileInputStream fromFile, FileOutputStream toFile) throws IOException {
FileChannel fromChannel = fromFile.getChannel();
FileChannel toChannel = toFile.getChannel();
try {
fromChannel.transferTo(0, fromChannel.size(), toChannel);
} finally {
try {
if (fromChannel != null) {
fromChannel.close();
}
} finally {
if (toChannel != null) {
toChannel.close();
}
}
}
}
/**
* Parses a file containing sql statements into a String array that contains
* only the sql statements. Comments and white spaces in the file are not
* parsed into the String array. Note the file must not contained malformed
* comments and all sql statements must end with a semi-colon ";" in order
* for the file to be parsed correctly. The sql statements in the String
* array will not end with a semi-colon ";".
*
* @param sqlFile
* - String containing the path for the file that contains sql
* statements.
*
* @return String array containing the sql statements.
*/
public static String[] parseSqlFile(String sqlFile) throws IOException {
return parseSqlFile(new BufferedReader(new FileReader(sqlFile)));
}
/**
* Parses a file containing sql statements into a String array that contains
* only the sql statements. Comments and white spaces in the file are not
* parsed into the String array. Note the file must not contained malformed
* comments and all sql statements must end with a semi-colon ";" in order
* for the file to be parsed correctly. The sql statements in the String
* array will not end with a semi-colon ";".
*
* @param sqlFile
* - InputStream for the file that contains sql statements.
*
* @return String array containing the sql statements.
*/
public static String[] parseSqlFile(InputStream sqlFile) throws IOException {
return parseSqlFile(new BufferedReader(new InputStreamReader(sqlFile)));
}
/**
* Parses a file containing sql statements into a String array that contains
* only the sql statements. Comments and white spaces in the file are not
* parsed into the String array. Note the file must not contained malformed
* comments and all sql statements must end with a semi-colon ";" in order
* for the file to be parsed correctly. The sql statements in the String
* array will not end with a semi-colon ";".
*
* @param sqlFile
* - Reader for the file that contains sql statements.
*
* @return String array containing the sql statements.
*/
public static String[] parseSqlFile(Reader sqlFile) throws IOException {
return parseSqlFile(new BufferedReader(sqlFile));
}
/**
* Parses a file containing sql statements into a String array that contains
* only the sql statements. Comments and white spaces in the file are not
* parsed into the String array. Note the file must not contained malformed
* comments and all sql statements must end with a semi-colon ";" in order
* for the file to be parsed correctly. The sql statements in the String
* array will not end with a semi-colon ";".
*
* @param sqlFile
* - BufferedReader for the file that contains sql statements.
*
* @return String array containing the sql statements.
*/
public static String[] parseSqlFile(BufferedReader sqlFile) throws IOException {
String line;
StringBuilder sql = new StringBuilder();
String multiLineComment = null;
while ((line = sqlFile.readLine()) != null) {
line = line.trim();
// Check for start of multi-line comment
if (multiLineComment == null) {
// Check for first multi-line comment type
if (line.startsWith("/*")) {
if (!line.endsWith("}")) {
multiLineComment = "/*";
}
// Check for second multi-line comment type
} else if (line.startsWith("{")) {
if (!line.endsWith("}")) {
multiLineComment = "{";
}
// Append line if line is not empty or a single line comment
} else if (!line.startsWith("--") && !line.equals("")) {
sql.append(line);
} // Check for matching end comment
} else if (multiLineComment.equals("/*")) {
if (line.endsWith("*/")) {
multiLineComment = null;
}
// Check for matching end comment
} else if (multiLineComment.equals("{")) {
if (line.endsWith("}")) {
multiLineComment = null;
}
}
}
sqlFile.close();
return sql.toString().split(";");
}
}
这篇关于发送带有数据库的应用程序的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
