我正在开发一个Android应用程序,我在资产文件夹中使用了现有的sqlite数据库。所以我实际上从该文件夹中复制数据库。用户还可以保存自己的数据(将任何内容标记为收藏)。
我在市场上上传了一个版本。现在我想在数据库中添加一些新数据并上传新版本。如果用户从市场更新应用程序,我想保留用户数据(从以前的版本)并添加新数据。我做了一些谷歌,发现升级方法应该做的伎俩。但是我正在从代码中更改DATABASE_VERSION,但是on upgrade方法没有得到调用。我想知道我错过了什么。这是我的代码:
public class DataBaseHelper extends SQLiteOpenHelper {
private static String DB_PATH = "/data/data/riskycoder.login/databases/";
public static String DB_NAME = "datenbank_EN.sqlite";
private SQLiteDatabase myDataBase;
private final Context myContext;
private static final int DATABASE_VERSION = 1;
public DataBaseHelper(Context context) {
super(context, DB_NAME, null, DATABASE_VERSION);
this.myContext = context;
}
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
} else {
this.getWritableDatabase();
try {
this.close();
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_READWRITE);
} catch (SQLiteException e) {
}
if (checkDB != null)
checkDB.close();
return checkDB != null ? true : false;
}
private void copyDataBase() throws IOException {
InputStream myInput = myContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[2048];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myOutput.close();
myInput.close();
//myDataBase.setVersion(DATABASE_VERSION);
}
public void openDataBase() throws SQLException {
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READWRITE);
Log.d("Test", "Database version: " +myDataBase.getVersion());
}
@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("Test", "in onUpgrade. Old is: " + oldVersion + " New is: " + newVersion);
}
}
答案 0 :(得分:18)
onUpgrade()
。按如下方式增加数据库版本:
private static final int DATABASE_VERSION = 2;
答案 1 :(得分:6)
将onUpgrade更改为以下
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
if(newVersion > oldVersion){
myContext.deleteDatabase(DB_NAME);
}
}
并且还改变你的createDataBase(),如下所示,
public void createDataBase() throws IOException{
boolean dbExist = checkDataBase();
if(dbExist){
// By calling this method here onUpgrade will be called on a
// writable database, but only if the version number has been increased
this.getWritableDatabase();
}
dbExist = checkDataBase();
if(!dbExist){
//By calling this method an empty database will be created into the default system path
//of the application so we will be able to overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
最后增加数据库版本并再次运行。在致电onUpgrade
或类似功能之前,getReadableDatabase()
不会被呼叫。
希望这有帮助
答案 2 :(得分:2)
试试这个(增加DATABASE_VERSION)&将调用onUpdate():
private static final int DATABASE_VERSION = 2;
答案 3 :(得分:2)
假设您确实更改了DATABASE_VERSION,您仍然需要在onUpgrade中放置代码才能实现。这不是神奇的,你必须告诉它该怎么做。
在您的情况下,您需要:
1)复制旧数据库(给它一个新名字)
2)复制新数据库
3)从旧数据库中读取数据
4)将任何差异复制到新数据库中
5)删除旧数据库
修改强>
假设您在资产文件夹中运送数据库,您可以复制它以供使用:
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// First copy old db
InputStream bakInput = getActivity().getAssets().open(dbname);
String bakFileName = getActivity().getAssets() + "YourDB.old";
OutputStream bakOutput = new FileOutputStream(bakFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = bakInput.read(buffer)) > 0) {
bakOutput.write(buffer, 0, length);
}
myOutput.flush();
myOutput.close();
myInput.close();
// delete the old db
File delDB = new File(getActivity().getAssets() + "YourDB");
boolean deleted = file.delete();
// Copy in the new db
InputStream myInput = getActivity().getAssets().open("YourDB");
String outFileName = MAIN_DB_PATH + dbname;
OutputStream myOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
myOutput.flush();
myOutput.close();
myInput.close();
// add code here to get changes user has made to db and move them to updated db
// delete the old db copy
File delDB = new File(getActivity().getAssets() + "YourDB.old");
boolean deleted = file.delete();
}