android jetpack project gives archlifecycleversion build error

问题

I am new to android development and just created my first "hello world" project in android studio 3.2 ( canary ) following this tutorial. https://developer.android.com/jetpack/docs/getting-started

and then I just did Build- > make project project tried to build and gave me following error.

Could not get unknown property 'archLifecycleVersion' for root project 'JetpackHelloWorld' of type org.gradle.api.Project.

UPDATE

Dependencies

following is the dependencies tag in my app folder build.gradle file

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.0'
    implementation 'android.arch.lifecycle:extensions:1.1.1'
    implementation "android.arch.lifecycle:extensions:$rootProject.archLifecycleVersion"
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

回答1:

Replace $rootProject.archLifecycleVersion with actual version, i guess this is 1.1.1 right now

回答2:

In your app Gradle file (build.gradle, you should see "app" to its right), you probably have

implementation 'android.arch.lifecycle:extensions:$rootProject.archLifecycleVersion'

Change it to:

implementation 'android.arch.lifecycle:extensions:1.1.1'

or add this to the top of your implementation line

def archLifecycleVersion = 1.1.1

回答3:

I think part (if not all) of the code is taken from this codelab: https://codelabs.developers.google.com/codelabs/android-room-with-a-view/

In the third part of the codelab, titled "Update gradle files" they use these lines (in the module's build.gradle) to import Room and Lifecycle components:

// Room components
implementation "android.arch.persistence.room:runtime:$rootProject.roomVersion"
annotationProcessor "android.arch.persistence.room:compiler:$rootProject.roomVersion"
androidTestImplementation "android.arch.persistence.room:testing:$rootProject.roomVersion"

// Lifecycle components
implementation "android.arch.lifecycle:extensions:$rootProject.archLifecycleVersion"
annotationProcessor "android.arch.lifecycle:compiler:$rootProject.archLifecycleVersion"

So, these "roomVersion" and "archLifecycleVersion" are variables that you have to define in the main build.gradle file. In the example they use these values:

ext {
   roomVersion = '1.0.0'
   archLifecycleVersion = '1.1.0'
}

But I've actually used "1.1.1" for both variables and it works.

来源：https://stackoverflow.com/questions/50329891/android-jetpack-project-gives-archlifecycleversion-build-error

标签

android

android-studio

kotlin

android-jetpack