Conflict with dependency 'com.android.support:support-annotations' in project ':app'. Resolved versions for app (26.1.0) and test app (27.1.1) differ.

Question

I am new to Android App Development. When I tried to create a new project,Android Project...the following message popped up..

Error:Execution failed for task \':app:

Answer 1

I have the same problem, in build.gradle (Module:app) add the following line of code inside dependencies:

dependencies 
{
   ...
   compile 'com.android.support:support-annotations:27.1.1'
}

It worked for me perfectly

Answer 2

Add this line under the dependencies in your gradle file

compile 'com.android.support:support-annotations:27.1.1'

Answer 3

If you using Android Studio 3.1.+ or above

just put this in your gradle depedencies:

implementation 'com.android.support:support-annotations:27.1.1'

Overall like this:

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'
    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'

    implementation 'com.android.support:support-annotations:27.1.1'
}

Answer 4

A better solution is explained in the official explanation. I left the answer I have given before under the horizontal line.

According to the solution there:

Use an external tag and write down the following code below in the top-level build.gradle file. You're going to change the version to a variable rather than a static version number.

ext {
    compileSdkVersion = 26
    supportLibVersion = "27.1.1"
}

Change the static version numbers in your app-level build.gradle file, the one has (Module: app) near.

android {
    compileSdkVersion rootProject.ext.compileSdkVersion // It was 26 for example
    // the below lines will stay
}

// here there are some other stuff maybe

dependencies {
    implementation "com.android.support:appcompat-v7:${rootProject.ext.supportLibVersion}"
    // the below lines will stay
}

Sync your project and you'll get no errors.

---

You don't need to add anything to Gradle scripts. Install the necessary SDKs and the problem will be solved.

In your case, install the libraries below from Preferences > Android SDK or Tools > Android > SDK Manager

Answer 5

Based on your screenshot i found two working solutions:

First solution: add to dependencies of your gradle module this line

compile 'com.android.support:support-annotations:27.1.1'

and sync your project

Note: if you are using Android studio 3+ change compile to implementation

Second solution: Configure project-wide properties found in the documentation https://developer.android.com/studio/build/gradle-tips.html#configure-project-wide-properties

in project gradle add this line:

// This block encapsulates custom properties and makes them available to all
// modules in the project.
ext {
    // The following are only a few examples of the types of properties you can define.
    compileSdkVersion = 26
    // You can also use this to specify versions for dependencies. Having consistent
    // versions between modules can avoid behavior conflicts.
    supportLibVersion = "27.1.1"
}

Then to access this section change compileSdkVersionline to be

compileSdkVersion rootProject.ext.compileSdkVersion

and at dependencies section change the imported library to be like this:

compile "com.android.support:appcompat-v7:${rootProject.ext.supportLibVersion}"

and sync your project

Note: if you are using Android studio 3+ change compile to implementation

For the difference between compile and implementation look at this What's the difference between implementation and compile in gradle

Answer 6

Adding this to build.gradle (Module app) worked for me:
compile 'com.android.support:support-annotations:27.1.1'