我在 4.0 版本中创建了一个 android 应用程序，并将我的 sqlite 数据库保存在 assets 文件夹中。当我尝试在 2.3 版本中运行我的应用程序时，我收到错误“复制数据库时出错”。我尝试将 checkdatabase 方法更改为以下方法，但仍然无效。请任何人都可以指导我解决这个问题。
public boolean checkDataBase()
{
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
DBadapter.java
公共类 DBAdapter 扩展 SQLiteOpenHelper {
private static String DB_PATH = "";
private static final String DB_NAME = "mydatabase.sqlite";
private SQLiteDatabase myDataBase1;
private final Context myContext1;
private static DBAdapter mDBConnection;
/**
* Constructor
* Takes and keeps a reference of the passed context in order to access to the application assets and resources.
* @param context
*/
private DBAdapter(Context context) {
super(context, DB_NAME, null, 1);
this.myContext1 = context;
DB_PATH = "/data/data/"
+ context.getApplicationContext().getPackageName()
+ "/databases/";
// The Android's default system path of your application database is
// "/data/data/mypackagename/databases/"
}
/**
* getting Instance
* @param context
* @return DBAdapter
*/
public static synchronized DBAdapter getDBAdapterInstance(Context context) {
if (mDBConnection == null) {
mDBConnection = new DBAdapter(context);
}
return mDBConnection;
}
/**
* Creates an 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 following method
// 1) an empty database will be created into the default system path of your application
// 2) than we 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 + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
// database does't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
/*public boolean checkDataBase()
{
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}*/
/**
* 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 = myContext1.getAssets().open(DB_NAME);
// Path to the just created empty db
String outFileName = DB_PATH + DB_NAME;
// 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();
}
/**
* Open the database
* @throws SQLException
*/
public void openDataBase() throws SQLException {
String myPath = DB_PATH + DB_NAME;
myDataBase1 = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
/**
* Close the database if exist
*/
@Override
public synchronized void close() {
if (myDataBase1 != null)
myDataBase1.close();
super.close();
}
/**
* Call on creating data base for example for creating tables at run time
*/
@Override
public void onCreate(SQLiteDatabase db) {
}
/**
* can used for drop tables then call onCreate(db) function to create tables again - upgrade
*/
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}
// ----------------------- CRUD Functions ------------------------------
/**
* This function used to select the records from DB.
* @param tableName
* @param tableColumns
* @param whereClase
* @param whereArgs
* @param groupBy
* @param having
* @param orderBy
* @return A Cursor object, which is positioned before the first entry.
*/
public Cursor selectRecordsFromDB(String tableName, String[] tableColumns,
String whereClase, String whereArgs[], String groupBy,
String having, String orderBy) {
return myDataBase1.query(tableName, tableColumns, whereClase, whereArgs,
groupBy, having, orderBy);
}
/**
* select records from db and return in list
* @param tableName
* @param tableColumns
* @param whereClase
* @param whereArgs
* @param groupBy
* @param having
* @param orderBy
* @return ArrayList<ArrayList<String>>
*/
public ArrayList<ArrayList<String>> selectRecordsFromDBList(String tableName, String[] tableColumns,
String whereClase, String whereArgs[], String groupBy,
String having, String orderBy) {
ArrayList<ArrayList<String>> retList = new ArrayList<ArrayList<String>>();
ArrayList<String> list = new ArrayList<String>();
Cursor cursor = myDataBase1.query(tableName, tableColumns, whereClase, whereArgs,
groupBy, having, orderBy);
if (cursor.moveToFirst()) {
do {
list = new ArrayList<String>();
for(int i=0; i<cursor.getColumnCount(); i++){
list.add( cursor.getString(i) );
}
retList.add(list);
} while (cursor.moveToNext());
}
if (cursor != null && !cursor.isClosed()) {
cursor.close();
}
return retList;
}
/**
* This function used to insert the Record in DB.
* @param tableName
* @param nullColumnHack
* @param initialValues
* @return the row ID of the newly inserted row, or -1 if an error occurred
*/
public long insertRecordsInDB(String tableName, String nullColumnHack,
ContentValues initialValues) {
return myDataBase1.insert(tableName, nullColumnHack, initialValues);
}
/**
* This function used to update the Record in DB.
* @param tableName
* @param initialValues
* @param whereClause
* @param whereArgs
* @return true / false on updating one or more records
*/
/*public boolean updateRecordInDB(String tableName,
ContentValues initialValues, String whereClause, String whereArgs[]) {
return myDataBase.update(tableName, initialValues, whereClause,
whereArgs) > 0;
}*/
/**
* This function used to update the Record in DB.
* @param tableName
* @param initialValues
* @param whereClause
* @param whereArgs
* @return 0 in case of failure otherwise return no of row(s) are updated
*/
/*public int updateRecordsInDB(String tableName,
ContentValues initialValues, String whereClause, String whereArgs[]) {
return myDataBase.update(tableName, initialValues, whereClause, whereArgs);
}*/
/**
* This function used to delete the Record in DB.
* @param tableName
* @param whereClause
* @param whereArgs
* @return 0 in case of failure otherwise return no of row(s) are deleted.
*/
/*public int deleteRecordInDB(String tableName, String whereClause,
String[] whereArgs) {
return myDataBase.delete(tableName, whereClause, whereArgs);
}*/
// --------------------- Select Raw Query Functions ---------------------
/**
* apply raw Query
* @param query
* @param selectionArgs
* @return Cursor
*/
public Cursor selectRecordsFromDB(String query, String[] selectionArgs) {
return myDataBase1.rawQuery(query, selectionArgs);
}
/**
* apply raw query and return result in list
* @param query
* @param selectionArgs
* @return ArrayList<ArrayList<String>>
*/
public ArrayList<ArrayList<String>> selectRecordsFromDBList(String query, String[] selectionArgs) {
ArrayList<ArrayList<String>> retList = new ArrayList<ArrayList<String>>();
ArrayList<String> list = new ArrayList<String>();
Cursor cursor = myDataBase1.rawQuery(query, selectionArgs);
if (cursor.moveToFirst()) {
do {
list = new ArrayList<String>();
for(int i=0; i<cursor.getColumnCount(); i++){
list.add( cursor.getString(i) );
}
retList.add(list);
} while (cursor.moveToNext());
}
if (cursor != null && !cursor.isClosed()) {
cursor.close();
}
return retList;
}
}
提前致谢