Android Studio 3.0 unknown element <library> found

Question

After I updated Android Studio, one of my projects cannot be built. The error message is:

Error:(20) error: unknown element <library> found.
Error:(20) unknown element <library> found.
Error:java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: com.android.tools.aapt2.Aapt2Exception: AAPT2 error: check logs for details
Error:java.util.concurrent.ExecutionException: com.android.tools.aapt2.Aapt2Exception: AAPT2 error: check logs for details
Error:com.android.tools.aapt2.Aapt2Exception: AAPT2 error: check logs for details
Error:Execution failed for task ':app:processDebugResources'.
    > Failed to execute aapt

My SDK version is 25. I have tried to invalidate cache and add distributionUrl=https://services.gradle.org/distributions/gradle-4.1-rc-2-all.zip, and both of them don't work for me.

Here is my dependencies:

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:25.4.0'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
compile 'com.android.support:support-v4:25.4.0'
compile 'de.hdodenhof:circleimageview:2.2.0'
testCompile 'junit:junit:4.12'

annotationProcessor "com.github.Raizlabs.DBFlow:dbflow-processor:${dbflow_version}"
compile "com.github.Raizlabs.DBFlow:dbflow-core:${dbflow_version}"
compile "com.github.Raizlabs.DBFlow:dbflow:${dbflow_version}"

compile fileTree(dir: 'libs', include: ['*.jar'])
compile 'com.android.support:appcompat-v7:25.4.0'
compile 'com.android.support:design:25.4.0'

compile 'com.microsoft.projectoxford:face:1.3.0'
}

This is the error log after removing DBFlow:

Error:(20) error: unknown element <library> found.
Error:(20) unknown element <library> found.
Error:java.util.concurrent.ExecutionException: java.util.concurrent.ExecutionException: com.android.tools.aapt2.Aapt2Exception: AAPT2 error: check logs for details
Error:java.util.concurrent.ExecutionException: com.android.tools.aapt2.Aapt2Exception: AAPT2 error: check logs for details
Error:com.android.tools.aapt2.Aapt2Exception: AAPT2 error: check logs for details
Error:Execution failed for task ':app:processDebugResources'.
    > Failed to execute aapt

Answer 1

Add this code in gradle.properties in the root project:

android.enableAapt2=false

Answer 2

In android studio version 3.1.2 the solution

android.enableAapt2=false

is no longer working.

The root cause of this problem is the Manifest MERGE, which happens when you try to include other dependencies in your project.

To inspect the error

1. Open AndroidManifest.xml

2. On bottom of the window select Merged Manifest Tab

3. Browse your manifest file now, and check the portion of manifest being in the slightly red background or lookup for library tag.

4. Right click and select Go To Declaration. Inspect the file and check which library/depencency it belongs to.

5. Either remove that library or update it from the repo.

Hope this helps.