Room "Not sure how to convert a Cursor to this method's return type": which method?
AndroidDaoAndroid RoomKaptAndroid Architecture-ComponentsAndroid Problem Overview
Error:Not sure how to convert a Cursor to this method's return type
Error:Execution failed for task ':app:compileDebugJavaWithJavac'.
Compilation failed; see the compiler error output for details.
Using Room
I'm getting this error and I'd like to find out which method causes it.
I have multiple DAO
s, with approximately 60 methods in total, and this error just popped up after adding a method (copy&pasted from another one that worked perfectly, just changed the field to set).
I could post the whole class of DAO
s, but I'm asking for a way to know which method failed. I tried with Run with --stacktrace
, Run with --info
and --debug option
, but none of these show any valuable information.
The method I added is a @Query
UPDATE
with Int
return type, as suggested in the documentation
> UPDATE or DELETE queries can return void or int. If it is an int, the value is the number of rows affected by this query.
EDIT: I'd like to add that I tried deleting the method, bringing the DAO back to the working state, but it still gives me this error.
EDIT2: Adding gradle console output because unreadable in comments:
error: Not sure how to convert a Cursor to this method's return type
error: Not sure how to convert a Cursor to this method's return type
2 errors
:app:compileDebugJavaWithJavac FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:compileDebugJavaWithJavac'.
Compilation failed; see the compiler error output for details.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
* Get more help at https://help.gradle.org
BUILD FAILED in 22s
Android Solutions
Solution 1 - Android
Recently I've had the same problem but I was using Coroutines
within the Dao
function, e.g.:
@Query("SELECT * FROM Dummy")
suspend fun get(): LiveData<List<Dummy>>
And was unable to compile, but after removing the suspend
everything worked just fine. It's not needed when returning LiveData
. suspend
and LiveData
seem not to work together (as of now).
Solution 2 - Android
I Spend the entire day on this issue. the solution was very simple. I was using something like this before
@Query("SELECT * FROM myTable")
fun getAll(): MutableLiveData<ArrayList<myData>>
Now when I changed ArrayList to List & MutableLiveData to LiveData it is working fine.
@Query("SELECT * FROM myTable")
fun getAll(): LiveData<List<myData>>
based on the answers & comments on this issue I think room support only List & LiveData because I tried with on MutableLiveData & only ArrayList too. none of the combinations worked.
Hope this will help someones few hours.
Solution 3 - Android
For anyone landing here, using a coroutine Flow as a return type, you will get this error if you accidentally make the function suspend. Since it is returning a flow, there is no need to suspend.
So instead of this:
@Query("SELECT * FROM myTable WHERE id = :id")
suspend fun findById(id: Long): Flow<MyDataType>
use this (without suspend modifier):
@Query("SELECT * FROM myTable WHERE id = :id")
fun findById(id: Long): Flow<MyDataType>
Solution 4 - Android
Yup, based on what you have mentioned in the comments, you are not allowed to change the return type from List
to anything else inside the Dao
. I'd assume Room doesn't know how to deal with other return types. Take the List
and cast/convert it into your desired type outside of the Dao
.
Solution 5 - Android
It is gone after I updated to latest version Room - room_version = "2.4.0"
Solution 6 - Android
In my case i was this problem when i used LiveData<ArrayList<Example Class>>
in Dao class for getting all things from Room and i fixed this when i change ArrayList
with List
.
Example(Kotlin):
@Dao
interface ExampleDao {
@Query("SELECT * from example_table")
fun getAllExample():LiveData<List<Example>>
}
Solution 7 - Android
@Query("select * from movie_action")
suspend fun getMovieActionRoom() : LiveData<List<MoviesActionModel>>
just remove suspend and the error will be gone in some cases.
Solution 8 - Android
For me it was because of mixing AndroidX with Pre-AndroidX. After a full migration and performing this, everything was back to normal. (Of course I moved to AndroidX-Room as well)
Solution 9 - Android
I've got a different use case for my apps.
So, I'm trying to return the actual Cursor
type.
E.g:
@Query("SELECT * FROM tbl_favourite")
abstract suspend fun selectAll(): Cursor
The above code will always throw Error:Not sure how to convert a android.database.Cursor to this method's return type
But as I recall correctly, the official docs also stated here that Room supports Cursor
.
After trying to debug the error log, and open up the MyTableDao_Impl.java
file I've found that looks like Cursor
are having an unhealthy relationship with suspend
keywords.
Thus, I've corrected my code to be like this:
@Query("SELECT * FROM tbl_favourite")
abstract fun selectAll(): Cursor
And voila, it works.
Solution 10 - Android
In my case I was using androidx
dependencies for Room
and android.arch.
[old] dependencies for ViewModel
and LiveData
so I got this message
Solution:
Either use all androidx
dependencies OR use all old dependencies of andrio.arch
Solution 11 - Android
in case someone actually needs MutableLiveData<List<T>>
in their ViewModel when working with Room
and using Kotlin
and coroutines
, this is how I've solved it
In the Dao I get MutableList with suspend
In the repository I change the context to Dispatchers.IO
and extract the list with suspend
in the ViewModel I use postValue
with the list in the init, syntax is below
ViewModel
private val allItems = MutableLiveData<List<DocumentItem>>()
init {
viewModelScope.launch {
allItems.postValue(repository.getAll())
}
}
Repository
suspend fun getAll(): MutableList<DocumentItem> = withContext(Dispatchers.IO) {
dao.getAll()
}
Dao
@Query("SELECT * FROM document_items ORDER BY id DESC")
suspend fun getAll(): MutableList<DocumentItem>
Solution 12 - Android
For my case, after got "Not sure how to convert a Cursor to this method's return type”:
delete the "build" and re-build, the error disappear.
Solution 13 - Android
Add the below code inside defaultConfig in build.gradle
javaCompileOptions.annotationProcessorOptions.includeCompileClasspath = true
Solution 14 - Android
For me, I was using wrong return type for queries.
Solution 15 - Android
Make sure if there is
> There is a problem with the query: [SQLITE_ERROR] SQL error or missing > database (no such table: METRO)
error in your build log before the error you mentioned in your description. If it is, you may have forgotten to add your new entity Pojo to database class. something like this
@Database(entities = {Table.class,ForgottenTable.class}, version = 1)
public abstract class Database extends RoomDatabase {
//class codes
}
Solution 16 - Android
Make sure you are not using suspend together with LiveData
@Query("SELECT * FROM ...")
fun getAllTellsByReceiver(receiverUid: String): LiveData<List<Tell>>
Solution 17 - Android
class IdAndFullName {
public int uid;
@ColumnInfo(name = "full_name")
public String fullName;
}
// DAO
@Query("SELECT uid, name || lastName as full_name FROM user")
public IdAndFullName[] loadFullNames();
If there is a mismatch between the query result and the POJO, Room will give you this error message.
Or if you are using @SkipQueryVerification, you will also get this error.
Solution 18 - Android
Modify your Dao, use Flowable instead of observable and add the following dependency (room with rxjava support)
compile group: 'android.arch.persistence.room', name: 'rxjava2', version: '1.1.1'
Dao returns flowable:
@Query("SELECT * FROM TableX")
public abstract Flowable<List<EntityX>> getAllXs();
Solution 19 - Android
For me it was to change from MutableLiveData
Solution 20 - Android
I got this error when I was trying do some aggregate functions in the query, like sum and count and then using aliases in the column names.
select count(users.id) as userCount, ...
It so happens that the alias name like userCount
above, must match the field name in the model.
Solution 21 - Android
You have to include the @Relation annotation in the class returned by the method. It's the only way Room would know how to establish the relationship between the two.
Solution 22 - Android
In my case Room didn't know sure how to convert a Cursor to this method's return type i.e ArrayList
so I changed a little bit I converted to list to kotlin's MutableListOf
. Now it works fine.
Solution 23 - Android
In my case upgrading versions worked.
Previous
api 'androidx.room:room-runtime:2.0.0'
annotationProcessor 'androidx.room:room-compiler:2.0.0'
api 'androidx.room:room-rxjava2:2.0.0'
Now
api 'androidx.room:room-runtime:+'
annotationProcessor 'androidx.room:room-compiler:+'
api 'androidx.room:room-rxjava2:+'
+
means latest version and for me it was 2.4.2
Solution 24 - Android
This error goes away after I changed the Kotlin version from 1.5.21 back to 1.3.61