Time stretching, AndroidX, update gradle

android/build.gradle

@@ -8,7 +8,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.2.1'
+        classpath 'com.android.tools.build:gradle:3.5.0'
     }
 }
 
@@ -25,10 +25,16 @@ android {
     compileSdkVersion 28
 
     defaultConfig {
-        minSdkVersion 16
-        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
+        minSdkVersion 21
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
+
     lintOptions {
         disable 'InvalidPackage'
     }
+
+    compileOptions {
+        sourceCompatibility 1.8
+        targetCompatibility 1.8
+    }
 }