Btukfyl

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 DAOs, 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 DAOs, 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

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.

Add the below code inside defaultConfig in build.gradle

javaCompileOptions.annotationProcessorOptions.includeCompileClasspath = true

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.

 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.

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();

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>>

}