Room - Schema export directory is not provided to the annotation processor so we cannot export the schema

Question

I am using Android Database Component Room  I ve configured everything  but when I compile  Android Studio gives me this warning      Schema export directory is not provided to the annotation processor so   we cannot export the schema  You can either provide   room schemaLocation annotation processor argument OR set   exportSchema to false    As I understand it is the location where DB file will be located  How can it affect my app  What is the best practice here  Should I use the default location  false value

User · Answer

Probably you didn t add your room class to child RoomDatabase child class in  Database entities    your classes

User · Answer

As per the docs      You can set annotation processor argument  room schemaLocation  to tell Room to export the schema into a folder  Even though it is not mandatory  it is a good practice to have version history in your codebase and you should commit that file into your version control system  but don t ship it with your app      So if you don t need to check the schema and you want to get rid of the warning  just add exportSchema   false to your RoomDatabase  as follows    Database entities     YourEntity class    version   1  exportSchema   false  public abstract class AppDatabase extends RoomDatabase                If you follow  mikejonesguy answer below  you will follow the good practice mentioned in the docs     Basically you will get a  json file in your    app schemas  folder  And it looks something like this        formatVersion   1     database          version   1       identityHash    53db508c5248423325bd5393a1c88c03        entities                      tableName    sms table            createSql    CREATE TABLE IF NOT EXISTS    TABLE NAME     id  INTEGER PRIMARY KEY AUTOINCREMENT   message  TEXT   date  INTEGER   client id  INTEGER             fields                              fieldPath    id                columnName    id                affinity    INTEGER                                        fieldPath    message                columnName    message                affinity    TEXT                                        fieldPath    date                columnName    date                affinity    INTEGER                                        fieldPath    clientId                columnName    client id                affinity    INTEGER                                  primaryKey                columnNames                  id                          autoGenerate   true                     indices                foreignKeys                          setupQueries            CREATE TABLE IF NOT EXISTS room master table  id INTEGER PRIMARY KEY identity hash TEXT           INSERT OR REPLACE INTO room master table  id identity hash  VALUES 42    53db508c5248423325bd5393a1c88c03                   If my understanding is correct  you will get such a file with every database version update  so that you can easily follow the history of your db

User · Answer

If like me you recently moved certain classes to different packages ect  and you use android navigation  Make sure to change the argType to you match you new package address  from  app argType  quot com example app old Item quot    to  app argType  quot com example app new Item quot

User · Answer

In the build gradle file for your app module  add this to the defaultConfig section  under the android section   This will write out the schema to a schemas subfolder of your project folder  javaCompileOptions       annotationProcessorOptions           arguments      quot room schemaLocation quot    quot  projectDir schemas quot  toString             Like this          android                    compileSdkVersion  buildToolsVersion  etc       defaultConfig                    applicationId  miSdkVersion  etc                   javaCompileOptions               annotationProcessorOptions                   arguments      quot room schemaLocation quot    quot  projectDir schemas quot  toString                                                  buildTypes  compileOptions  etc

User · Answer

mikejonesguy answer is perfect  just in case you plan to test room migrations  recommended   add the schema location to the source sets      In your build gradle file you specify a folder to place these   generated schema JSON files  As you update your schema  you   ll end up   with several JSON files  one for every version  Make sure you commit   every generated file to source control  The next time you increase   your version number again  Room will be able to use the JSON file for   testing          Florina Muntenescu  source       build gradle  android                      defaultConfig                              javaCompileOptions               annotationProcessorOptions                   arguments     room schemaLocation     projectDir schemas  toString                                          add the schema location to the source sets        used by Room  to test migrations     sourceSets           androidTest assets srcDirs    files   projectDir schemas  toString

User · Answer

Kotlin  Here we go    android                compileSdkVersion  buildToolsVersion  etc       defaultConfig                    applicationId  miSdkVersion  etc           kapt               arguments                   arg  room schemaLocation     projectDir schemas                                      buildTypes                   buildTypes  compileOptions  etc                   Don t forget about plugin    apply plugin   kotlin-kapt   For more information about kotlin annotation processor please visit   Kotlin docs

User · Answer

I use  kts Gradle files  Kotlin Gradle DSL  and the kotlin-kapt plugin but I still get a script compilation error when I use Ivanov Maksim s answer   Unresolved reference  kapt   For me this was the only thing which worked   android       defaultConfig           javaCompileOptions               annotationProcessorOptions                   arguments   mapOf  room schemaLocation  to   projectDir schemas

User · Answer

Above answers are correct  This version is easy to follow   Because  Schema export directory is not provided to the annotation processor   So we need to provide the directory for schema export      Step  1  In your file which extends the RoomDatabase  change the line to      Database entities       class version   1  exportSchema   true     Or    Database entities       class version   1       because the default value is always true      Step  2  In your build gradle project       file  inside the defaultConfig     which is inside android    big section   add the javaCompileOptions    section  it will be like             android                  defaultConfig                          javaComplieOptions SECTION                       javaCompileOptions                               annotationProcessorOptions                                        arguments     room schemaLocation    projectDir schemas  toString                                                                                   Other SECTION                                                           projectDir is a variable name  you cannot change it  it will get your own project directory  schemas is a string  you can change it to any you like  For example    projectDir MyOwnSchemas  toString

[java] Room - Schema export directory is not provided to the annotation processor so we cannot export the schema

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