Room Persistence Library : Cannot resolve symbol Room

Question

I used Android Studio 3.0 Beta 2 with the following gradle settings

I can search the RxRoom but no Room class founded. After following the instruction Add Components , I cannot use Room class in my Fragment.

This class is in the seperate module, the app module does not contains any room library dependency.

The error showed "Cannot resolve symbol Room" in IDE.

build.gradle

apply plugin: 'com.android.library'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"


    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        javaCompileOptions {
            annotationProcessorOptions {
                arguments = ["room.schemaLocation":
                                     "$projectDir/schemas".toString()]
            }
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    compileOptions {
        targetCompatibility 1.8
        sourceCompatibility 1.8
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.0.2'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    implementation 'com.android.support:design:26.0.2'
    implementation 'com.android.support:support-v4:26.0.2'
    implementation 'com.android.support:recyclerview-v7:26.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation('com.android.support.test.espresso:espresso-core:3.0.1', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    implementation "android.arch.persistence.room:runtime:1.0.0-alpha9"
    annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha9"
    testImplementation "android.arch.persistence.room:testing:1.0.0-alpha9"
    implementation "android.arch.persistence.room:rxjava2:1.0.0-alpha9"
}

Updated I have tried to downgrade the room library to alpha8 first and the Room class come back now. I have no idea why this class disappeared in the alpha9 but at least it is the workaround.

Answer 1

After a week trial ,I find that I can run the apk even I have the compile time error. I tried to resolve the issue by the following way to resolve the compile error.

Change

annotationProcessor "android.arch.persistence.room:compiler:1.0.0-alpha9"

To

 implementation "android.arch.persistence.room:compiler:1.0.0-alpha9"

And add the following Disable the error check from Migrate to Android Plugin for Gradle 3.0

javaCompileOptions {
    annotationProcessorOptions {
        includeCompileClasspath = true
    }
}

Answer 2

Please change all the Room dependency from implementation into api in the build.gradle

Answer 3

If you are getting the error "Cannot resolve symbol" on your Room Entity classes, try this hack: add a dummy property to your class. Then clean and rebuild your project. This should refresh the entities. Then remove the dummy.

Example:

@Query("select * from my_entity where name = :name") --> Cannot resolve symbol name...
MyEntity getMyEntityByName(String name);  


@Entity(indices = {@Index(value = {"name"})}, tableName = "my_entity")
public class MyEntity {
    other properties        ....

    public int dummy; --> add and remove this