typeconverter | Java type conversion

In SQLite (and others that conform to SQL-92) null is considered different to any other null and hence your issue.

As such you should not be using null. You can overcome this setting the default value to a specific value that indicates a no supplied value.

For example you could use:-

First, Many special thanks to @Reza Aghaei for his awesome answers Thanks to him much.

"Specified cast is not valid" error in TypeConverter.ConvertTo

How to create TypeConverter which accepts multiple values and serialized to WinForms Form.designer.cs?

TypeConverter Implemented as following:

Yes, that's possible. But you need to modify the Id struct.

As far as I can understand you are using some generator to generate the source files. MyEntity for example. After generating the classes you need to manually modify Id struct. It should have an interface like this for example:

Its really too hard. But here's article explain some: https://www.codeproject.com/Articles/5372/How-to-Edit-and-Persist-Collections-with-Collectio

Third, the collection class must implement one or both of the following methods: Add and AddRange. Although IList interface has an Add member and CollectionBase implements IList, you still have to implement an Add method for your collection, given that CollectionBase declares an explicit member implementation of the IList’s Add member. The designer serializes the collection according to what method you have implemented. If you have implemented both, the AddRange is preferred.

When serializing with the Add method, for every item it uses a new line.

Yes, use:-

If you are using sql light db, then you have to migrate the db in this way,

I think the readAllData() method in your CredentialRepository is incorrect, because this function needs to return the query result to CredentialViewModel. Your correct approach is to pass the query result to ViewModel.

When trying to log in, you should also call the method defined in ViewModel and pass username and password to this method for retrieval. The final result defines a LiveData to represent whether you log in successfully.

Your issue would appear to be that @Insert(onConflict = OnConflictStrategy.REPLACE) is inserting instead of replacing.

The OnConflict strategy will only be actioned if there is a conflict. That is typically that a UNIQUE constraint is violated (see link below for other violations covered).

From your explanation of the issue there is no violation and thus instead of the row(s) being replaced, they are instead inserted.

• You may wish to refere to https://sqlite.org/lang_conflict.html

In short you need a UNIQUE index to cover your scenario to ensure that a violation occurs.

Without the Article class it is impossible to say what actual change is required. However the following example shows 2 classes (entities) and how a unique index can be added to a column/property articleName.

So first a guess as what your Article class could be:-

I believe that your issue is that you are importing the database from the assets and that the version number has been set to 1 in the imported database.

That is first Room is detecting that it cannot verify the data integrity because there the room_master_table table doesn't exist in the imported database.

• Otherwise Room checks the hash stored in the database against the value in the APK if they are not the same then the schema has changed.

Then Room finds that the database has a version number of 1 (as is stored in the header of the database file) and hence it saying that the version number has been changed. This being the real issue rather than the unable to verify the data integrity.

I believe that you need to change the version number to 0 in the database being imported. That is open it in DBBeaver, click on the Edit Pragmas and change the version number from 1 to 0. e.g. :-