Please check your the Room library version you use. In Room 2.1 and higher, you can use the suspend keyword to make your DAO queries asynchronous using Kotlin coroutines:

dependencies {
    def room_version = "2.4.2" // current stable version

    implementation "androidx.room:room-runtime:$room_version"
    implementation "androidx.room:room-ktx:$room_version"
    annotationProcessor "androidx.room:room-compiler:$room_version"
    ...
}

So I am working on Unit 5 Forge app project from Android Basics in Kotlin, in the DAO :

    // TODO: implement a method to insert a Forageable into the database
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    suspend fun insert(forageable: Forageable)

    //   TODO: implement a method to update a Forageable that is already in the database
    @Update
    suspend fun update(forageable: Forageable)

    // TODO: implement a method to delete a Forageable from the database.
    @Delete
    suspend fun delete(forageable: Forageable)

Compiling will generate this “error: Not sure how to handle insert method’s return type”. It happened for all Insert, Update and Delete.

If I removed the “suspend” keyword, then the errors will go away. But app will crash because “ Cannot access database on the main thread since it may potentially lock the UI for a long period of time.”

There is anther lab called Inventory app in the same Unit 5 that used the same design and it was working fine with the “suspend” keyword.

The Forage app was modeled after the Inventory app. On both projects, I used all the same dependencies and versions.

Any suggestions?

Edit: It is using coroutines.

private fun updateForage(forageable: Forageable) {
    viewModelScope.launch {
        forageableDao.update(forageable)
    }
}

Also have tried this:

@Delete
suspend fun delete(forageable: Forageable): Long