如果您的应用程序需要一个数据库，并且它带有内置数据，那么交付该应用程序的最佳方式是什么?我应该:
预创建SQLite数据库，并将其包含在。apk? 在应用程序中包含SQL命令，并让它在第一次使用时创建数据库并插入数据?
我所看到的缺点是:
可能的SQLite版本不匹配可能会导致问题，我目前不知道数据库应该去哪里以及如何访问它。 在设备上创建和填充数据库可能需要很长时间。
有什么建议吗?关于任何问题的文档指针将非常感激。
当前回答
我修改了类和问题的答案，并编写了一个允许通过DB_VERSION更新数据库的类。
public class DatabaseHelper extends SQLiteOpenHelper {
private static String DB_NAME = "info.db";
private static String DB_PATH = "";
private static final int DB_VERSION = 1;
private SQLiteDatabase mDataBase;
private final Context mContext;
private boolean mNeedUpdate = false;
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
if (android.os.Build.VERSION.SDK_INT >= 17)
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
else
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
this.mContext = context;
copyDataBase();
this.getReadableDatabase();
}
public void updateDataBase() throws IOException {
if (mNeedUpdate) {
File dbFile = new File(DB_PATH + DB_NAME);
if (dbFile.exists())
dbFile.delete();
copyDataBase();
mNeedUpdate = false;
}
}
private boolean checkDataBase() {
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
private void copyDataBase() {
if (!checkDataBase()) {
this.getReadableDatabase();
this.close();
try {
copyDBFile();
} catch (IOException mIOException) {
throw new Error("ErrorCopyingDataBase");
}
}
}
private void copyDBFile() throws IOException {
InputStream mInput = mContext.getAssets().open(DB_NAME);
//InputStream mInput = mContext.getResources().openRawResource(R.raw.info);
OutputStream mOutput = new FileOutputStream(DB_PATH + DB_NAME);
byte[] mBuffer = new byte[1024];
int mLength;
while ((mLength = mInput.read(mBuffer)) > 0)
mOutput.write(mBuffer, 0, mLength);
mOutput.flush();
mOutput.close();
mInput.close();
}
public boolean openDataBase() throws SQLException {
mDataBase = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.CREATE_IF_NECESSARY);
return mDataBase != null;
}
@Override
public synchronized void close() {
if (mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (newVersion > oldVersion)
mNeedUpdate = true;
}
}
使用类。
在活动类中，声明变量。
private DatabaseHelper mDBHelper;
private SQLiteDatabase mDb;
在onCreate方法中，编写以下代码。
mDBHelper = new DatabaseHelper(this);
try {
mDBHelper.updateDataBase();
} catch (IOException mIOException) {
throw new Error("UnableToUpdateDatabase");
}
try {
mDb = mDBHelper.getWritableDatabase();
} catch (SQLException mSQLException) {
throw mSQLException;
}
如果将数据库文件添加到res/raw文件夹中，则使用类的以下修改。
public class DatabaseHelper extends SQLiteOpenHelper {
private static String DB_NAME = "info.db";
private static String DB_PATH = "";
private static final int DB_VERSION = 1;
private SQLiteDatabase mDataBase;
private final Context mContext;
private boolean mNeedUpdate = false;
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
if (android.os.Build.VERSION.SDK_INT >= 17)
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
else
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
this.mContext = context;
copyDataBase();
this.getReadableDatabase();
}
public void updateDataBase() throws IOException {
if (mNeedUpdate) {
File dbFile = new File(DB_PATH + DB_NAME);
if (dbFile.exists())
dbFile.delete();
copyDataBase();
mNeedUpdate = false;
}
}
private boolean checkDataBase() {
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
private void copyDataBase() {
if (!checkDataBase()) {
this.getReadableDatabase();
this.close();
try {
copyDBFile();
} catch (IOException mIOException) {
throw new Error("ErrorCopyingDataBase");
}
}
}
private void copyDBFile() throws IOException {
//InputStream mInput = mContext.getAssets().open(DB_NAME);
InputStream mInput = mContext.getResources().openRawResource(R.raw.info);
OutputStream mOutput = new FileOutputStream(DB_PATH + DB_NAME);
byte[] mBuffer = new byte[1024];
int mLength;
while ((mLength = mInput.read(mBuffer)) > 0)
mOutput.write(mBuffer, 0, mLength);
mOutput.flush();
mOutput.close();
mInput.close();
}
public boolean openDataBase() throws SQLException {
mDataBase = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.CREATE_IF_NECESSARY);
return mDataBase != null;
}
@Override
public synchronized void close() {
if (mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (newVersion > oldVersion)
mNeedUpdate = true;
}
}
http://blog.harrix.org/article/6784
其他回答
Android已经提供了一种版本感知的数据库管理方法。这种方法已经在Android应用程序的BARACUS框架中得到了利用。
它使您能够在应用程序的整个版本生命周期中管理数据库，能够将sqlite数据库从任何以前的版本更新到当前版本。
此外，它还允许您运行SQLite的热备份和热恢复。
我不是100%确定，但是针对特定设备的热恢复可能使您能够在应用程序中发布准备好的数据库。但我不确定数据库二进制格式，这可能特定于某些设备，供应商或设备代。
因为这些东西是Apache许可证2，所以可以随意重用代码的任何部分，这些代码可以在github上找到
编辑:
如果您只想传送数据，可以考虑在应用程序第一次启动时实例化和持久化pojo。BARACUS有一个内置的支持(内置的键值存储配置信息，例如。"APP_FIRST_RUN"加上一个后上下文引导钩子，以便在上下文上运行后启动操作)。这使得你可以在应用中使用紧密耦合的数据;在大多数情况下，这符合我的用例。
如果所需的数据不是很大(限制我不知道，将取决于很多东西)，你也可以从网站/网络应用下载数据(XML, JSON，无论什么)。接收到数据后，使用接收到的数据执行SQL语句，创建表并插入数据。
如果你的移动应用程序包含大量数据，稍后用更准确的数据或更改更新已安装的应用程序中的数据可能会更容易。
我修改了类和问题的答案，并编写了一个允许通过DB_VERSION更新数据库的类。
public class DatabaseHelper extends SQLiteOpenHelper {
private static String DB_NAME = "info.db";
private static String DB_PATH = "";
private static final int DB_VERSION = 1;
private SQLiteDatabase mDataBase;
private final Context mContext;
private boolean mNeedUpdate = false;
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
if (android.os.Build.VERSION.SDK_INT >= 17)
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
else
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
this.mContext = context;
copyDataBase();
this.getReadableDatabase();
}
public void updateDataBase() throws IOException {
if (mNeedUpdate) {
File dbFile = new File(DB_PATH + DB_NAME);
if (dbFile.exists())
dbFile.delete();
copyDataBase();
mNeedUpdate = false;
}
}
private boolean checkDataBase() {
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
private void copyDataBase() {
if (!checkDataBase()) {
this.getReadableDatabase();
this.close();
try {
copyDBFile();
} catch (IOException mIOException) {
throw new Error("ErrorCopyingDataBase");
}
}
}
private void copyDBFile() throws IOException {
InputStream mInput = mContext.getAssets().open(DB_NAME);
//InputStream mInput = mContext.getResources().openRawResource(R.raw.info);
OutputStream mOutput = new FileOutputStream(DB_PATH + DB_NAME);
byte[] mBuffer = new byte[1024];
int mLength;
while ((mLength = mInput.read(mBuffer)) > 0)
mOutput.write(mBuffer, 0, mLength);
mOutput.flush();
mOutput.close();
mInput.close();
}
public boolean openDataBase() throws SQLException {
mDataBase = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.CREATE_IF_NECESSARY);
return mDataBase != null;
}
@Override
public synchronized void close() {
if (mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (newVersion > oldVersion)
mNeedUpdate = true;
}
}
使用类。
在活动类中，声明变量。
private DatabaseHelper mDBHelper;
private SQLiteDatabase mDb;
在onCreate方法中，编写以下代码。
mDBHelper = new DatabaseHelper(this);
try {
mDBHelper.updateDataBase();
} catch (IOException mIOException) {
throw new Error("UnableToUpdateDatabase");
}
try {
mDb = mDBHelper.getWritableDatabase();
} catch (SQLException mSQLException) {
throw mSQLException;
}
如果将数据库文件添加到res/raw文件夹中，则使用类的以下修改。
public class DatabaseHelper extends SQLiteOpenHelper {
private static String DB_NAME = "info.db";
private static String DB_PATH = "";
private static final int DB_VERSION = 1;
private SQLiteDatabase mDataBase;
private final Context mContext;
private boolean mNeedUpdate = false;
public DatabaseHelper(Context context) {
super(context, DB_NAME, null, DB_VERSION);
if (android.os.Build.VERSION.SDK_INT >= 17)
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
else
DB_PATH = "/data/data/" + context.getPackageName() + "/databases/";
this.mContext = context;
copyDataBase();
this.getReadableDatabase();
}
public void updateDataBase() throws IOException {
if (mNeedUpdate) {
File dbFile = new File(DB_PATH + DB_NAME);
if (dbFile.exists())
dbFile.delete();
copyDataBase();
mNeedUpdate = false;
}
}
private boolean checkDataBase() {
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
private void copyDataBase() {
if (!checkDataBase()) {
this.getReadableDatabase();
this.close();
try {
copyDBFile();
} catch (IOException mIOException) {
throw new Error("ErrorCopyingDataBase");
}
}
}
private void copyDBFile() throws IOException {
//InputStream mInput = mContext.getAssets().open(DB_NAME);
InputStream mInput = mContext.getResources().openRawResource(R.raw.info);
OutputStream mOutput = new FileOutputStream(DB_PATH + DB_NAME);
byte[] mBuffer = new byte[1024];
int mLength;
while ((mLength = mInput.read(mBuffer)) > 0)
mOutput.write(mBuffer, 0, mLength);
mOutput.flush();
mOutput.close();
mInput.close();
}
public boolean openDataBase() throws SQLException {
mDataBase = SQLiteDatabase.openDatabase(DB_PATH + DB_NAME, null, SQLiteDatabase.CREATE_IF_NECESSARY);
return mDataBase != null;
}
@Override
public synchronized void close() {
if (mDataBase != null)
mDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if (newVersion > oldVersion)
mNeedUpdate = true;
}
}
http://blog.harrix.org/article/6784
我终于做到了!!我已经使用这个链接帮助在Android应用程序中使用自己的SQLite数据库，但必须稍微改变一下。
If you have many packages you should put the master package name here: private static String DB_PATH = "data/data/masterPakageName/databases"; I changed the method which copies the database from local folder to emulator folder! It had some problem when that folder didn't exist. So first of all, it should check the path and if it's not there, it should create the folder. In the previous code, the copyDatabase method was never called when the database didn't exist and the checkDataBase method caused exception. so I changed the code a little bit. If your database does not have a file extension, don't use the file name with one.
它对我很有用，我希望它对你也有用
package farhangsarasIntroduction;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.HashMap;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteException;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
public class DataBaseHelper extends SQLiteOpenHelper{
//The Android's default system path of your application database.
private static String DB_PATH = "data/data/com.example.sample/databases";
private static String DB_NAME = "farhangsaraDb";
private SQLiteDatabase myDataBase;
private final Context myContext;
/**
* 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, 1);
this.myContext = context;
}
/**
* Creates a empty database on the system and rewrites it with your own database.
* */
public void createDataBase() {
boolean dbExist;
try {
dbExist = checkDataBase();
} catch (SQLiteException e) {
e.printStackTrace();
throw new Error("database dose not exist");
}
if(dbExist){
//do nothing - database already exist
}else{
try {
copyDataBase();
} catch (IOException e) {
e.printStackTrace();
throw new Error("Error copying database");
}
//By calling this method and empty database will be created into the default system path
//of your application so we are gonna be able to overwrite that database with our database.
this.getReadableDatabase();
}
}
/**
* Check if the database already exist to avoid re-copying the file each time you open the application.
* @return true if it exists, false if it doesn't
*/
private boolean checkDataBase(){
SQLiteDatabase checkDB = null;
try{
String myPath = DB_PATH +"/"+ DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}catch(SQLiteException e){
//database does't exist yet.
throw new Error("database does't exist yet.");
}
if(checkDB != null){
checkDB.close();
}
return checkDB != null ? true : false;
}
/**
* 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{
//copyDataBase();
//Open your local db as the input stream
InputStream myInput = myContext.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH +"/"+ DB_NAME;
File databaseFile = new File( DB_PATH);
// check if databases folder exists, if not create one and its subfolders
if (!databaseFile.exists()){
databaseFile.mkdir();
}
//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();
}
@Override
public synchronized void close() {
if(myDataBase != null)
myDataBase.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
you to create adapters for your views.
}
2017年11月，谷歌发布了房间持久性库。
从文档中可以看到:
Room持久库在SQLite上提供了一个抽象层 允许流畅的数据库访问，同时利用 SQLite。 该库可以帮助您在设备上创建应用程序数据的缓存 这个缓存，作为你的应用程序的单一 真实源，允许用户查看一致的密钥副本 应用程序中的信息，不管用户是否有 互联网连接。
当第一次创建或打开数据库时，Room数据库具有回调。可以使用create回调填充数据库。
Room.databaseBuilder(context.applicationContext,
DataDatabase::class.java, "Sample.db")
// prepopulate the database after onCreate was called
.addCallback(object : Callback() {
override fun onCreate(db: SupportSQLiteDatabase) {
super.onCreate(db)
// moving to a new thread
ioThread {
getInstance(context).dataDao()
.insert(PREPOPULATE_DATA)
}
}
})
.build()
这篇博文中的代码。
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