我在Android 3.0+上遇到了db4o問題,因爲事實證明,在創建db4o數據庫時,默認情況下會使用某些網絡apis。 (我偶然發現了這個帖子:http://mavistechchannel.wordpress.com/2011/11/18/db4o-at-honeycomb-and-ice-cream-sandwich/關於它)Android上的db4o 3.0+問題
但是,我試圖讓數據庫創建請求異步,但我想我遇到了一個問題,因爲它在它完全創建之前調用數據庫DB。 (我現在得到一個鎖定錯誤)有什麼辦法可以做到這一點同步?或者,至少等到它完成了?這裏是我的db4o幫手:
public class Db4oHelperAsync implements Constants{
private static final String USE_INTERNAL_MEMORY_FOR_DATABASE = "USE_INTERNAL_MEMORY_FOR_DATABASE";
private static ObjectContainer oc = null;
private Context context;
/**
* @param ctx
*/
public Db4oHelperAsync(Context ctx) {
context = ctx;
}
/**
* Create, open and close the database
*/
public ObjectContainer db() {
if (oc == null || oc.ext().isClosed()) {
if (Utilities.getPreferences(context).getBoolean(USE_INTERNAL_MEMORY_FOR_DATABASE, true)) {
new GetDbFromInternalMemory().execute();
} else {
new GetDbFromSDCard().execute();
}
return oc;
} else {
return oc;
}
}
/**
* Configure the behavior of the database
*/
private EmbeddedConfiguration dbConfig() throws IOException {
EmbeddedConfiguration configuration = Db4oEmbedded.newConfiguration();
configuration.common().objectClass(PersistentObjectWithCascadeOnDelete.class).objectField("name").indexed(true);
configuration.common().objectClass(PersistentObjectWithCascadeOnDelete.class).cascadeOnUpdate(true);
configuration.common().objectClass(PersistentObjectWithCascadeOnDelete.class).cascadeOnActivate(true);
configuration.common().objectClass(PersistentObjectWithCascadeOnDelete.class).cascadeOnDelete(true);
configuration.common().objectClass(PersistentObjectWithoutCascadeOnDelete.class).objectField("name").indexed(true);
configuration.common().objectClass(PersistentObjectWithoutCascadeOnDelete.class).cascadeOnUpdate(true);
configuration.common().objectClass(PersistentObjectWithoutCascadeOnDelete.class).cascadeOnActivate(true);
return configuration;
}
/**
* Returns the path for the database location
*/
private String db4oDBFullPathInternal(Context ctx) {
return ctx.getDir("data", 0) + "/" + "testapp.db4o";
}
private String db4oDBFullPathSdCard(Context ctx) {
File path = new File(Environment.getExternalStorageDirectory(), ".testapp");
if (!path.exists()) {
path.mkdir();
}
return path + "/" + "testapp.db4o";
}
/**
* Closes the database
*/
public void close() {
if (oc != null)
oc.close();
}
private class GetDbFromInternalMemory extends AsyncTask<Void, Void, ObjectContainer>{
@Override
protected ObjectContainer doInBackground(Void... params) {
try {
ObjectContainer obj = Db4oEmbedded.openFile(dbConfig(), db4oDBFullPathInternal(context));
CLog.v("USING INTERNAL MEMORY FOR DATABASE");
return obj;
} catch (Exception ie) {
ie.printStackTrace();
CLog.e(Db4oHelper.class.getName(), ie.toString());
return null;
}
}
@Override
protected void onPostExecute(ObjectContainer result)
{
oc = result;
}
}
private class GetDbFromSDCard extends AsyncTask<Void, Void, ObjectContainer>{
@Override
protected ObjectContainer doInBackground(Void... params) {
try {
ObjectContainer obj = Db4oEmbedded.openFile(dbConfig(), db4oDBFullPathSdCard(context));
CLog.v("USING SDCARD FOR DATABASE");
SharedPreferences.Editor edit = Utilities.getPreferencesEditor(context);
edit.putBoolean(USE_INTERNAL_MEMORY_FOR_DATABASE, true);
edit.commit();
return obj;
} catch (Exception ie) {
ie.printStackTrace();
CLog.e(Db4oHelper.class.getName(), ie.toString());
return null;
}
}
@Override
protected void onPostExecute(ObjectContainer result)
{
oc = result;
}
}
}
感謝您的幫助 - 我沒有完全遵循這一點,但足夠接近。這有點令人沮喪,但是,哦! – Hosemeyer 2011-12-22 18:56:57