How to find the Android version of a project in Android Studio?

//https://stackoverflow.com/questions/19465049/changing-api-level-android-studio

Changing API level Android Studio

When you want to update your minSdkVersion in an existing Android project...

Update build.gradle (Module: YourProject) under Gradle Script and

make sure that it is NOT build.gradle (Project: YourProject.app).

An example of build.gradle:

apply plugin: 'com.android.application'

android {

    compileSdkVersion 28

    buildToolsVersion "28.0.2"

    defaultConfig {

        applicationId "com.stackoverflow.answer"

        minSdkVersion 21

        targetSdkVersion 28

        versionCode 1

        versionName "1.0"

    }

    buildTypes {

        release {

            minifyEnabled false

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

    }

}

dependencies {

    androidTestCompile 'junit:junit:4.12'

    compile fileTree(dir: 'libs', include: ['*.jar'])

}

Rebuild project

After updating the build.gradle's minSdkVersion, you have to click on the button to sync gradle file ("Sync Project with Gradle files"). That will clear the marker.

Updating manifest.xml, for e.g. deleting any references to SDK levels in the manifest file, is NOT necessary anymore in Android Studio.