Android support

[SgtSilvio]

The following has to added to the app build.gradle file

android {
    ...
    packagingOptions {
        exclude 'META-INF/INDEX.LIST'
        exclude 'META-INF/io.netty.versions.properties'
    }
}

And of course this permission has to be added to the AndroidManifest.xml
<uses-permission android:name="android.permission.INTERNET"/>

[SgtSilvio]

Android should be added to the documentation

[SgtSilvio]

Netty and JCTools can not be proguarded well, so add these proguard rules:

-keepclassmembernames class io.netty.** {
    *;
}

-keepclassmembernames class org.jctools.** {
    *;
}

[SgtSilvio]

Works on API 24+ (Android 7.0+)

Lambdas, method references, static and default methods can be compiled to lower versions by specifying:

android {
    ...
    compileOptions {
        sourceCompatibility 1.8
        targetCompatibility 1.8
    }
    ...
}

Unfortunately java.util.function.*, java.util.Optional, java.util.concurrent.CompletableFuture are only available on API 24+
Reference: https://developer.android.com/studio/write/java8-support

[SgtSilvio]

Ignore this comment, Proguard 6.1 does not seem to work smoothly

Proguard 6.1 supports backporting streams (including java.util.function.*, java.util.Optional)
Unfortunately java.util.concurrent.CompletableFuture can not be backported yet.
https://www.guardsquare.com/en/blog/proguard-61-released

The following needs to be specified in gradle.properties:

android.enableR8=false
android.enableR8.libraries=false

The following needs to be specified in the top-level build.gradle:

buildscript {
    ...
    dependencies {
        classpath 'com.android.tools.build:gradle:3.4.1'
        classpath 'net.sf.proguard:proguard-gradle:6.1.1'
    }
    configurations.all {
        resolutionStrategy {
            force 'net.sf.proguard:proguard-gradle:6.1.1'
        }
    }
    ...
}

The following proguard rule needs to be added:

-target 1.7

Also other proguard rules are necessary, but it is not clear yet, which are necessary.

[shriharsha-bhagwat]

So there is no way i can use following/similar on API level < 23 ?

mClient.toAsync().subscribeWith()
                            .topicFilter(topic)
                            .qos(MqttQos.EXACTLY_ONCE)
                            .callback(new Consumer<Mqtt3Publish>() {
                                @Override
                                public void accept(Mqtt3Publish mqtt3Publish) {
                                    //Do something
                                    Log.e(HiveMqttService.class.getSimpleName(),
                                            mqtt3Publish.getTopic().toString());
                                }
                            })
                            .send()
                            .whenComplete((subAck, throwable) -> {
                                if (throwable == null) {
                                     //Do something
                                    Log.e(HiveMqttService.class.getSimpleName(), "Subscribed " + topic);
                                } else {
                                    Log.e(HiveMqttService.class.getSimpleName(), "Error on " + topic + " " + throwable.getMessage());
                                }
                             });

[SgtSilvio]

The gradle plugin Android RetroFix can backport java.util.function.*, java.util.Optional, java.util.concurrent.CompletableFuture and more.

[shriharsha-bhagwat]

Wow cool. Thanks a lot. This MQTT Client Library is the best.

[SgtSilvio]

Android Support is now documented here: https://hivemq.github.io/hivemq-mqtt-client/docs/installation/android.html