Bump Android build and improve AndroidX compatibility.

Author: julienzarka

android/build.gradle

@@ -21,7 +21,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.5.0'
+        classpath 'com.android.tools.build:gradle:3.5.1'
         classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.10'
     }
 }
@@ -37,10 +37,11 @@ apply plugin: 'com.android.library'
 apply plugin: 'com.google.protobuf'
 
 android {
-    compileSdkVersion 28
+    compileSdkVersion 29
 
     defaultConfig {
         minSdkVersion 19
+        targetSdkVersion 29
         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
     lintOptions {
@@ -77,5 +78,7 @@ protobuf {
 }
 
 dependencies {
+    def core_version = "1.1.0"
+    implementation "androidx.core:core:$core_version"
     implementation 'com.google.protobuf:protobuf-lite:3.0.1'
 }

android/gradle/wrapper/gradle-wrapper.properties

@@ -2,4 +2,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.2-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-all.zip

android/src/main/AndroidManifest.xml

@@ -1,6 +1,6 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
   package="com.pauldemarco.flutter_blue">
-  <uses-sdk android:minSdkVersion="18" />
+  <uses-sdk android:minSdkVersion="19" />
   <uses-permission android:name="android.permission.BLUETOOTH" />
   <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
   <uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>