diff --git a/.travis.yml b/.travis.yml
index 848c0b3..961f749 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,14 @@
 language: android
+
 android:
   components:
-    - platform-tools
-    - tools
+    - build-tools-28.0.3
+    - android-28
+    - extra-android-m2repository
+  licenses:
+    - 'android-sdk-license-.+'
+
+jdk: oraclejdk8
+
+script:
+  - ./gradlew clean build
diff --git a/build.gradle b/build.gradle
index e4467f8..5b4d80f 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,15 +1,16 @@
-// Top-level build file where you can add configuration options common to all sub-projects/modules.
 buildscript {
     repositories {
+        google()
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.1'
+        classpath 'com.android.tools.build:gradle:3.4.2'
     }
 }
 
 allprojects {
     repositories {
+        google()
         jcenter()
     }
 }
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 0c71e76..541c09d 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-2.2.1-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-5.5.1-all.zip
diff --git a/safeslinger-exchange/build.gradle b/safeslinger-exchange/build.gradle
index d20aa73..7e13946 100644
--- a/safeslinger-exchange/build.gradle
+++ b/safeslinger-exchange/build.gradle
@@ -1,11 +1,11 @@
 apply plugin: 'com.android.library'
 
 android {
-    compileSdkVersion rootProject.ext.compileSdkVersion
+    compileSdkVersion 28
 
     defaultConfig {
         minSdkVersion 8
-        targetSdkVersion 25
+        targetSdkVersion 28
     }
     sourceSets {
         main {
diff --git a/safeslinger-exchange/build.xml b/safeslinger-exchange/build.xml
deleted file mode 100644
index c46d848..0000000
--- a/safeslinger-exchange/build.xml
+++ /dev/null
@@ -1,92 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project name="safeslinger-exchange" default="help">
-
-    <!-- The local.properties file is created and updated by the 'android' tool.
-         It contains the path to the SDK. It should *NOT* be checked into
-         Version Control Systems. -->
-    <property file="local.properties" />
-
-    <!-- The ant.properties file can be created by you. It is only edited by the
-         'android' tool to add properties to it.
-         This is the place to change some Ant specific build properties.
-         Here are some properties you may want to change/update:
-
-         source.dir
-             The name of the source directory. Default is 'src'.
-         out.dir
-             The name of the output directory. Default is 'bin'.
-
-         For other overridable properties, look at the beginning of the rules
-         files in the SDK, at tools/ant/build.xml
-
-         Properties related to the SDK location or the project target should
-         be updated using the 'android' tool with the 'update' action.
-
-         This file is an integral part of the build system for your
-         application and should be checked into Version Control Systems.
-
-         -->
-    <property file="ant.properties" />
-
-    <!-- if sdk.dir was not set from one of the property file, then
-         get it from the ANDROID_HOME env var.
-         This must be done before we load project.properties since
-         the proguard config can use sdk.dir -->
-    <property environment="env" />
-    <condition property="sdk.dir" value="${env.ANDROID_HOME}">
-        <isset property="env.ANDROID_HOME" />
-    </condition>
-
-    <!-- The project.properties file is created and updated by the 'android'
-         tool, as well as ADT.
-
-         This contains project specific properties such as project target, and library
-         dependencies. Lower level build properties are stored in ant.properties
-         (or in .classpath for Eclipse projects).
-
-         This file is an integral part of the build system for your
-         application and should be checked into Version Control Systems. -->
-    <loadproperties srcFile="project.properties" />
-
-    <!-- quick check on sdk.dir -->
-    <fail
-            message="sdk.dir is missing. Make sure to generate local.properties using 'android update project' or to inject it through the ANDROID_HOME environment variable."
-            unless="sdk.dir"
-    />
-
-    <!--
-        Import per project custom build rules if present at the root of the project.
-        This is the place to put custom intermediary targets such as:
-            -pre-build
-            -pre-compile
-            -post-compile (This is typically used for code obfuscation.
-                           Compiled code location: ${out.classes.absolute.dir}
-                           If this is not done in place, override ${out.dex.input.absolute.dir})
-            -post-package
-            -post-build
-            -pre-clean
-    -->
-    <import file="custom_rules.xml" optional="true" />
-
-    <!-- Import the actual build file.
-
-         To customize existing targets, there are two options:
-         - Customize only one target:
-             - copy/paste the target into this file, *before* the
-               <import> task.
-             - customize it to your needs.
-         - Customize the whole content of build.xml
-             - copy/paste the content of the rules files (minus the top node)
-               into this file, replacing the <import> task.
-             - customize to your needs.
-
-         ***********************
-         ****** IMPORTANT ******
-         ***********************
-         In all cases you must update the value of version-tag below to read 'custom' instead of an integer,
-         in order to avoid having your file be overridden by tools such as "android update project"
-    -->
-    <!-- version-tag: 1 -->
-    <import file="${sdk.dir}/tools/ant/build.xml" />
-
-</project>
diff --git a/safeslinger-exchange/project.properties b/safeslinger-exchange/project.properties
deleted file mode 100644
index b2ef7dc..0000000
--- a/safeslinger-exchange/project.properties
+++ /dev/null
@@ -1,15 +0,0 @@
-# This file is automatically generated by Android Tools.
-# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
-#
-# This file must be checked in Version Control Systems.
-#
-# To customize properties used by the Ant build system edit
-# "ant.properties", and override values to adapt the script to your
-# project structure.
-#
-# To enable ProGuard to shrink and obfuscate your code, uncomment this (available properties: sdk.dir, user.home):
-#proguard.config=${sdk.dir}/tools/proguard/proguard-android.txt:proguard-project.txt
-
-# Project target.
-target=android-23
-android.library=true