我有一个android应用程序，它有sqllite数据库，位于assets文件夹中。我已经在playstore中发布了数据库版本= null的应用程序，而不是数据库版本= 1，数据库版本= 2，现在想要发布数据库版本= 3的应用程序。我有条件删除最后的数据并在更新时复制新数据。如果用户安装了版本2的应用程序，如果用户拥有版本1数据库而不是在主活动上停止运行，则其工作正常。复制数据库的条件有什么问题？ 我的数据库帮助程序类是这样的。 感谢
lable
答案 0 :(得分：0)
首先，检查运行的数据库用户的版本 之后更新数据库
if(DATABASE_VERSION == 1)
{
try {
copyDataBaseForVersion1();
DATABASE_VERSION = 3;
} catch (IOException e) {
throw new Error("Error copying database");
}
}
else if(DATABASE_VERSION == 2)
{
try {
copyDataBaseForVersion2();
DATABASE_VERSION = 3;
} catch (IOException e) {
throw new Error("Error copying database");
}
}
答案 1 :(得分：0)
我认为更好的方法是：
你可以使用这样的东西
在数据库文件中升级/更改时，更改DATABASE_VERSION值。
public class Cls_DatabaseHelper extends SQLiteOpenHelper {
private static String DB_PATH = "";
private static final int DATABASE_VERSION = 1;
private static String DB_NAME = "mydatabase.db";
public static SQLiteDatabase myDataBase;
private static Cls_DatabaseHelper myDBHelper = null;
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
*/
private Cls_DatabaseHelper(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
DB_PATH = myContext.getDatabasePath(DB_NAME).getPath();
try {
openDataBase();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static Cls_DatabaseHelper getInstance(Context context) {
if (myDBHelper == null) {
myDBHelper = new Cls_DatabaseHelper(context.getApplicationContext());
}
return myDBHelper;
}
/**
* Creates a empty database on the system and rewrites it with your own
* database.
* */
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
// 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();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
/**
* 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;
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY
| SQLiteDatabase.NO_LOCALIZED_COLLATORS);
int DB_EXIST_VERSION = PreferenceManager
.getDefaultSharedPreferences(myContext).getInt(
"DB_VERSION", 0);
if (DATABASE_VERSION != DB_EXIST_VERSION) {
checkDB = null;
}
} catch (SQLiteException e) {
// 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 {
// 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;
// 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();
PreferenceManager.getDefaultSharedPreferences(myContext).edit()
.putInt("DB_VERSION", DATABASE_VERSION).commit();
}
public void openDataBase() throws SQLException, IOException {
createDataBase();
// Open the database
String myPath = DB_PATH;
myDataBase = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READWRITE
| SQLiteDatabase.NO_LOCALIZED_COLLATORS);
}
@Override
public synchronized void close() {
if (myDataBase != null)
myDataBase.close();
myDataBase = null;
myDBHelper = null;
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
/*********************************************
* Method to execute a SQL statemtn and return a custom adapter. Use only to
* search Station Codes
*********************************************/
public Cursor executeSQLStatement(String SQLStatement) {
Cursor c = null;
try {
if (myDataBase != null) {
c = myDataBase.rawQuery(SQLStatement, new String[] {});
if (c != null)
c.moveToFirst();
}
}
catch (Exception e) {
e.printStackTrace();
}
return c;
}
}