How to ignore some columns during inserting date - android-room

Question

When you use Android Room auto generated insert method, it pass all values to all columns For example, if you have an entity like below:
#Entity
public class Task {
#PrimaryKey(autoGenerate = true)
public long id;
#NonNull
#ColumnInfo(defaultValue = "Unknown Title")
public String name;
#NonNull
#ColumnInfo(defaultValue = "Does not have any description!")
public String desc;
#ColumnInfo(defaultValue = "false")
public boolean isDone;
}
And you try to insert an empty instance of Task class by:
taskDao.insert(new Task());
It will run a query like this:
INSERT INTO Task (id, name, desc, isDone) values (null, null, null, 0);
that is against of our table structure rules, so we get error:
Caused by: android.database.sqlite.SQLiteConstraintException: NOT NULL constraint failed: task.name (code 1299 SQLITE_CONSTRAINT_NOTNULL)
While if it use this query:
INSERT INTO Task DEFAULT VALUES;
or
INSERT INTO Task (id) VALUES (null);
SQLite creates a row with all default values, without any errors.
But to ignore null variables in the insert query for using default valuse?

Answer 1

Try this:
#Entity
public class Task {
public String mName = "Unknown Title";
public String mDescription = "Does not have any description!";
public boolean mIsDone = "false";
#PrimaryKey(autoGenerate = true) //must be placed at the end!!
public long id = 0;
}
And create object like this:
Task task = new Task() //all use default values
Task task = new Task(name) //use default values for other fileds
Task task = new Task(name, description) //the order matters, otherwise you need to explicitlty specify the filed, like following
Task task = new Task(mIsDone = true, mName = "Sam")
Room "deaultValue" is not for entity use:
https://developer.android.com/reference/androidx/room/ColumnInfo#defaultValue()

Answer 2

Based on what is written in the Android documentation:
The default value you specify here will NOT be used if you simply insert the Entity with #Insert.
That means there are no simple way but you can do it in some ways:
Assign Variables Values
Assign what you defined as default values in #ColumnInfo, for those variables value, because if you doesn't update those values, the default assignment will be used, as Documentation says:
If you simply insert the Entity with #Insert ... any value assigned in Java/Kotlin will be used.
#Entity
public class Task {
#PrimaryKey(autoGenerate = true)
public long id;
#NonNull
#ColumnInfo(defaultValue = "Unknown Title")
public String name = "Unknown Title";
#NonNull
#ColumnInfo(defaultValue = "Does not have any description!")
public String description = "Does not have any description!";
#ColumnInfo(defaultValue = "false")
public boolean isDone; // it doesn't need assignment
// boolean values are false as default
}
Special Query
As Documentation recommend:
Use #Query with an INSERT statement and skip this column there in order to use this default value.
#Query("INSERT INTO task DEFAULT VALUES")
long insert();
or
#Query("INSERT INTO task (id) VALUES (null)")
long insert();
As you told in your question.
Simplified Class (ref)
#Insert(entity = Task.class)
long insert(NewTask task);
#Entity
class NewTask {
int id = 0;
}
it runs
INSERT INTO task (id) VALUES (null);