remirisque / neko

The Clojure/Android Toolkit

Neko: The Clojure/Android Toolkit

Neko is a toolkit designed to make Android development using Clojure easier and more fun. It accomplishes this by making adding Clojure support to your Android project easy and providing functional wrappers and alternatives to Android’s Java API.

Features

Warning

Note that the libraries are under heavy development. APIs are subject to change. In particular, neko.threading will be changed.

The toolkit comes as two components:

1. Simplified build support for Clojure using Android’s Ant-based build system, and

2. The following Clojure libraries:

   • neko.compilation helps set up dynamic compilation.

   • neko.context helps retrieve resources from the application’s context.

   • neko.listeners contains namespaces that take the tedium to adding callback code to various widgets.

   • neko.log interns functions that make logging from your code clean and simple.

   • neko.threading will contain utilities to manage asynchronous tasks and working with UI threads.

Requirements

Using Neko requires the following:

Clojure 1.2 or newer

Clojure 1.2 works on Android 2.2 and newer. Clojure 1.3 and newer work on Android 2.3 and newer.

If you would like to use dynamic compilation with Android 2.3 and newer, use the Clojure available from the android branch from this repository on GitHub. This branch is based off the latest Clojure development version.

If you would like to use dynamic compilation, but must support Android 2.1, you will need to use the version from branch android-1.2.x, available here. This is based off of Clojure 1.2.1.

Android SDK Tools

Neko has been developed with the latest revision of the Android SDK tools, and is compatible with r17 and up of the Android SDK.

Warning

Revisions 14 and 17 of the Android SDK introduced changes in the Ant build system. Neko has been updated to use the build system in r17. You will probably need to change your project if you have been using an older version of Neko/SDK. For more detailed information, check the Android Tools Project site for information about the breaking changes in r14 and r17.

Android Platform SDK 7 (2.1/Eclair) or newer

In order to maintain backwards-compatibility, Neko does not support any APIs for newer versions of the platform.

Getting started with Neko

The following instructions should help you to add Clojure support to your project’s build and allow you to use the libraries within your application.

1. Install the Android SDK

You can get this from directly from Google. You will need to be sure to also install a platform for development. The CyanogenMod wiki has some more detailed instructions.

2. Get Neko

Just clone the repository to your computer:

% git clone https://github.com/clojure-android/neko.git

If all went well, Neko should now be in a directory called neko.

3. Add Clojure

Now, go into the neko directory and created a directory called libs. Copy clojure.jar into that directory. If you don’t already have Clojure installed, you can download it from the project’s page.

4. Create your project

Next, you will need to create a new Android project using the android command from the Android SDK, as follows:

% android create project -p <directory> -t <target> -k <package> -a <activity>

The arguments to this command are:

<directory>

The name of the directory for your new project.

<target>

The target API version you will use for development. For example, you could use android-15 to target the Android 4.0.3 platform. You can see a list of targets available by running android list targets.

<package>

This unique string will be used to identify your application. You should follow the package naming conventions. An example may be com.example.cool_clojure_app.

<activity>

This is the name of a class that will be the entry point of your application.

Once you run this, you will see a bunch of output as the SDK generates your project, for example:

% android create project -p hello -k com.example.hello_clojure -a HelloActivity -t android-15
Created project directory: hello
Created directory /home/dan/devel/android/hello/src/com/example/hello_clojure
Added file hello/src/com/example/hello_clojure/HelloActivity.java
Created directory /home/dan/devel/android/hello/res
Created directory /home/dan/devel/android/hello/bin
Created directory /home/dan/devel/android/hello/libs
Created directory /home/dan/devel/android/hello/res/values
Added file hello/res/values/strings.xml
Created directory /home/dan/devel/android/hello/res/layout
Added file hello/res/layout/main.xml
Created directory /home/dan/devel/android/hello/res/drawable-hdpi
Created directory /home/dan/devel/android/hello/res/drawable-mdpi
Created directory /home/dan/devel/android/hello/res/drawable-ldpi
Added file hello/AndroidManifest.xml
Added file hello/build.xml
Added file hello/proguard-project.txt

5. Add Neko as a library for your project

Change into the new directory for your project and calculate the relative path to the directory where you cloned Neko. Now, run the following command:

% android update project -p . -l <../relative/path/to/neko>

For example:

% cd hello
% android update project -p . -l ../neko
Resolved location of library project to: /home/user/work/neko
Updated project.properties
Updated local.properties
Updated file ./proguard-project.txt

6. Get Ant to build your Clojure code

To enable Neko’s build support for Clojure, you will need to make two modifications to the build.xml file in your project directory.

1. You must add a line to similar to the following before the line with <import file="${sdk.dir}/tools/ant/build.xml" />.

   <import file="/path/to/neko/build-support/clojure.xml"/>

   The important thing is that the value of the file attribute should resolve to the clojure.xml in the build-support directory of this repository. It may be either a relative or absolute path.

2. You must find the line that reads <!-- version-tag: 1 --> and change the 1 to custom. If you do not do this, Android may overwrite your changes.

7. Get rid of that Java file

You may have noticed that when you created the project file, Android generated a Java file corresponding to the package and activity name. Delete it. For example:

% rm -r src/com

8. Create a source directory for you Clojure files

By default, Neko looks in src/clojure.

% mkdir src/clojure

9. Write your first Android application in Clojure

For replicate the default activity that the SDK created in Clojure, you will need to create a source file with the same namespace as the original file. For example, given the package com.example.hello_clojure and the activity HelloActivity, you would create the file src/clojure/com/example/hello_clojure/HelloActivity.clj as follows:

(ns com.example.hello_clojure.HelloActivity
  (:gen-class :main false
              :extends android.app.Activity
              :exposes-methods {onCreate superOnCreate})
  (:import [com.example.hello_clojure R$layout]))

(defn -onCreate
  [this bundle]
  (doto this
    (.superOnCreate bundle)
    (.setContentView R$layout/main)))

As a gist: https://gist.github.com/2361385

10. Build and run it

You can now run and install the application to a running emulator or a connected device using:

% ant debug install

If all went well, you should be able to find your application in the launcher. When you run it, after several seconds, you should see a simple ‘Hello World’ appear.

11. Make something wonderful

From this point on, it is up to you to create something wonderful.

Advanced topics

Here are some more things you can do with Neko:

clojure.properties

You can place a clojure.properties file in the build-support directory from Neko (where clojure.xml lives). This file will be sourced and used in any project in which you have enabled Clojure build support.

Reflection warnings

To enable reflection warnings during compilation, simply set the clojure.warn.reflection property to true. This is something that might be good to put in that clojure.properties file.

Mixed Java/Clojure projects

Neko will build all Java sources you have placed in src/java before any Clojure sources.

Legal information

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