Execution failed for task 'encountered using room': app:kaptdebugkotlin‘

Narrow path , Leave one step to let people go ;
When the taste is strong , Cut three points and invite people to taste .

1. Step on thunder

Project use Room database , You need to add a new operation method, and then make the corresponding Dao Some changes have been made , It turns out like this ：

Execution failed for task ':app:kaptReleaseKotlin'.
> A failure occurred while executing org.jetbrains.kotlin.gradle.internal.KaptExecution
   > java.lang.reflect.InvocationTargetException (no error message)

Nima oh ,no error message It looks spicy and dazzling , Brilliant …

2. Demining

StackOverflow The plan This time, I really can't count on it .

Chairman Mao taught us : Do it yourself , Have ample food and clothing . Then roll up your sleeves and work hard …

In general , encounter build Errors in the process , Our correct posture is like this .

1. open Android Studio On the right side of the Gradle;
2. Find build, Conduct build And so on ;

As shown in the figure below :

Double click here build after , The details come out , It is extremely convenient to help us locate the problem .

error : Not sure how to convert a Cursor to this method’s return type (void).

3. summary

According to the above error location , It's easy to solve the problem …

The reason for the error ：

SELECT The query needs to have a return value . Default return Cursor.

The document is described as follows ：

For SELECT queries, Room will infer the result contents from the method’s return type and generate the code that will automatically convert the query result into the method’s return type. For single result queries, the return type can be any data object (also known as POJOs). For queries that return multiple values, you can use List or Array. In addition to these, any query may return Cursor or any query result can be wrapped in a LiveData.

INSERT queries can return void or long. If it is a long, the value is the SQLite rowid of the row inserted by this query. Note that queries which insert multiple rows cannot return more than one rowid, so avoid such statements if returning long.

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.

Just to summarize ：

1. SELECT Inquire about ： Any query can return Cursor perhaps LiveData Results after packaging .
   1. Single result query ： Return the data object directly (POJOs)
   2. Multiple result queries : have access to List perhaps Array
2. INSERT Inquire about : No return value (void) perhaps long( Line number rowid)
3. UPDATE and DELETE Inquire about : No return value (void) perhaps int( Rows affected )

Detailed document address :Query

4. Room Related knowledge

1. Room Persistence Library
2. Use Room Save data to local database
3. Room API file

Consider taking time , Write it specifically Room