我尝试通过将资产文件夹从资产文件夹复制到设备来使用SQLite数据库。如果正在复制db，我还使用DDMS进行了检查。一切都很好但是当我打开复制的数据库时，里面没有表格，即它是一个空白数据库。
请帮我如何复制数据库及其表格。
这是我的DBHelper类： -
public class DBHelper extends SQLiteOpenHelper {
private static String DB_NAME = "collegeDb2";
private SQLiteDatabase db;
private final Context context;
private String DB_PATH;
public DBHelper(Context context) {
super(context, DB_NAME, null, 1);
this.context = context;
DB_PATH = context.getApplicationInfo().dataDir + "/databases/";
}
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
} else {
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
private boolean checkDataBase() {
File dbFile = new File(DB_PATH + DB_NAME);
return dbFile.exists();
}
private void copyDataBase() throws IOException {
InputStream myInput = context.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
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();
}
public Cursor getColleges() {
String myPath = DB_PATH + DB_NAME;
db = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
Cursor c = db.rawQuery("SELECT * FROM collegeslist", null);
// Note: colleges is the one table in External db. Here we trying to access the records of table from external db.
return c;
}
public Cursor getProducts() {
String myPath = DB_PATH + DB_NAME;
db = SQLiteDatabase.openDatabase(myPath, null,
SQLiteDatabase.OPEN_READONLY);
Cursor d = db.rawQuery("SELECT * FROM productslist", null);
// Note: products is the one table in External db. Here we trying to access the records of table from external db.
return d;
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
我可以在onCreate()中使用此代码添加表格： -
public void onCreate(SQLiteDatabase db) {
String CREATE_collegeslistTable = "CREATE TABLE collegeslist ( "
+ "_id INTEGER PRIMARY KEY NOT NULL ,Organization_Name VARCHAR DEFAULT (null) ,Organization_No VARCHAR DEFAULT (null) ,Assigned_To VARCHAR DEFAULT (null) ,Billing_Address VARCHAR DEFAULT (null) ,Billing_City VARCHAR DEFAULT (null) )";
db.execSQL(CREATE_collegeslistTable);
String CREATE_productslistTable = "CREATE TABLE productslist ( "
+ "_id INTEGER PRIMARY KEY NOT NULL ,Product_Name VARCHAR DEFAULT (null) ,Part_Number VARCHAR DEFAULT (null) ,Manufacturer VARCHAR DEFAULT (null) ,Product_Category VARCHAR DEFAULT (null) ,Vendor_Name VARCHAR DEFAULT (null), Unit_Price DOUBLE DEFAULT (null), Usage_Unit VARCHAR DEFAULT (null), Unit INTEGER DEFAULT (null) )";
db.execSQL(CREATE_productslistTable);
}
但这只会在db中创建两个空白表，我也想要它们内部的数据。由于表中有数百个条目，因此我无法手动添加它们。
请有人帮忙....
答案 0 :(得分：0)
您需要在数据库名称中附加db文件的路径：
private static String DB_NAME = "collegeDb2";
应该是：
private static String DB_NAME = "<path_where_you_are_copying_db>/collegeDb2.db";
示例：如果您在此处复制了您的db文件：/storage/sdcard0/test.db，那么它应该是：
private static String DB_NAME = "/storage/sdcard0/test.db"
此外，您不需要createDatabase()方法。如果数据库被调用super时不存在，将自动创建数据库
答案 1 :(得分：0)
所以我最后通过使用以下DBHelper课程来实现它： -
public class DBHelper extends SQLiteOpenHelper {
public SQLiteDatabase database = null;
public File databaseFile;
public static String databaseName = "collegeDb.sqlite";
public String databasePath = "";
Context mContext;
public DBHelper(Context paramContext) {
super(paramContext, databaseName, null, 1);
this.mContext = paramContext;
Log.d("data", "package name:" + paramContext.getPackageName());
this.databasePath = ("data/data/" + paramContext.getPackageName() + "/databases/"+databaseName);
this.databaseFile = new File(this.databasePath);
if (!this.databaseFile.exists())
try {
deployDataBase(DBHelper.databaseName, this.databasePath);
return;
} catch (IOException localIOException) {
localIOException.printStackTrace();
}
}
private void deployDataBase(String dbNAme, String dbPath)
throws IOException {
InputStream localInputStream = this.mContext.getAssets().open(dbNAme);
FileOutputStream localFileOutputStream = new FileOutputStream(dbPath);
byte[] arrayOfByte = new byte[1024];
while (true) {
int i = localInputStream.read(arrayOfByte);
if (i <= 0) {
localFileOutputStream.flush();
localFileOutputStream.close();
localInputStream.close();
return;
}
localFileOutputStream.write(arrayOfByte, 0, i);
}
}
@Override
public synchronized void close() {
if (database != null)
database.close();
super.close();
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO Auto-generated method stub
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO Auto-generated method stub
}
/**
* Getting all colleges
* returns list of colleges
* */
public List<String> getAllColleges(){
List<String> colleges = new ArrayList<String>();
// Select All Query
String selectQuery = "SELECT * FROM collegeslist";
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
colleges.add(cursor.getString(1));
} while (cursor.moveToNext());
}
// closing connection
cursor.close();
db.close();
// returning colleges
return colleges;
}
/**
* Getting all products
* returns list of products
* */
public List<String> getAllProducts(){
List<String> products = new ArrayList<String>();
// Select All Query
String selectQuery = "SELECT * FROM productslist";
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
products.add(cursor.getString(1));
} while (cursor.moveToNext());
}
// closing connection
cursor.close();
db.close();
// returning products
return products;
}
}
感谢您的帮助朋友。