我使用本教程： 教程自定义数据库
我从资产文件夹复制数据库并将其复制到我的设备（或模拟器）。一切都是正确的。我从 DDMS 的角度来看我的数据库。但我有时也想升级我的数据库，所以我做了：
super(context, DB_NAME, null, 2); //changed version from 1 to 2
并修改 onUpgrade 方法：
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if(newVersion > oldVersion){
this.myContext.deleteDatabase(DB_NAME);
try {
this.copyDataBase();
} catch (IOException e) {
e.printStackTrace();
}
}
}
但运行后，我的设备上仍有旧版本的数据库。如何删除旧版本的数据库并复制新版本。DB_NAME 是我的数据库名称（带格式，但不带路径）， copyDataBase() 是将数据库复制到设备的方法（它可以工作）。
我粘贴我的所有代码：
public class DataBaseHelper extends SQLiteOpenHelper{
private static String DB_PATH = "/data/data/sitcom.quiz/databases/";
private static String DB_NAME = "sitcoms.sqlite";
private SQLiteDatabase myDataBase;
private final Context myContext;
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, 4);
this.myContext = context;
}
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
//do nothing - database already exist
}else{
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
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;
}
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 + 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();
}
public void openDataBase() throws SQLException{
//Open the database
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY);
}
@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) {
Log.d("adas", "dasd");
if(newVersion > oldVersion){
String myPath = DB_PATH + DB_NAME;
this.myContext.deleteDatabase(myPath);
try {
this.copyDataBase();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
和我的活动：
DataBaseHelper myDbHelper = new DataBaseHelper(this);
myDbHelper = new DataBaseHelper(this);
try {
myDbHelper.createDataBase();
} catch (IOException ioe) {
throw new Error("Unable to create database");
}
try {
myDbHelper.openDataBase();
}catch(SQLException sqle){
throw sqle;
}
谢谢，如果你能给我理由或只是暗示为什么这不起作用。