Compiling Your libGDX Project

So now that you have imported a libGDX project into Android Studio, you will probably notice that it doesn't look like a normal Android Studio project, and also that it won't compile right away.

This tutorial will explain the changes needed to be made so that you can compile your libGDX project for Android, desktop and HTML.

Android:

So if you tried to compile your new project you probably got a Gradle error that looks something like this:

What happens here is that currently (as of early 2018) projects imported from libGDX use a Gradle version of something like 2.14.1 and libGDX needs a Gradle version of 3.5 or above. Conversely, you will also get an error if you are using any Gradle version above 4.0, which would be the default of Android Studio. In either case, we want to change the Gradle version. To do this, we open the 'gradle-wrapper.properties' file under the 'Gradle Scripts' heading in the Project window.

We want to change the distributionURL line to:

distributionUrl=https\://services.gradle.org/distributions/gradle-3.5-all.zip

If you followed my previous tutorial in setting up the libGDX project in Android Studio, this should be all you need to do in order to make the APK able to be compiled.

If you are still having trouble, here are some other problems I have faced.

Error:(2, 0) Plugin with id 'jetty' not found

This error is caused when you are using a Gradle version above 4.0. Follow the steps above to change the Gradle version to 3.5, but additionally follow these steps:

1. Open the project level 'build.gradle' file (again under the 'Gradle Scripts' heading in the Project window)
2. Change the 'classpath' version:

classpath 'com.android.tools.build:gradle:2.3.3'

3. In the same file, under 'repositories' remove:

google()

NOTE: There are two places to do #3, under 'buildscript' and under 'allprojects'

Error: Plugin with id 'gwt' not found

If you run into this error, there is a simple solution. Just go into the project level 'build.gradle' file (again under the 'Gradle Scripts' heading in the Project window) and add the following line under the 'dependencies' inside the 'buildscript' tag:

classpath 'de.richsource.gradle.plugins:gwt-gradle-plugin:0.6'

Desktop: 

The easiest way to compile to desktop is to create a runnable JAR file. To do this, open the Gradle window by clicking the vertical 'Gradle' button on the right side. In that menu, expand ':desktop', then expand 'other', and finally click on 'dist'.

Once it is finished compiling, you can find the JAR file in this directory:

[APPLICATION PATH]/desktop/build/libs

If you end up having an error, read below.

Running the desktop app from Android Studio

This is easy, once you know what to do. Go into the Project Window and expand the 'Desktop' folder. Several folders will open and at the end there will be a java file 'DesktopLauncher'. Right click that and select 'Run DesktopLauncher.main()'. Unfortunately, this will cause an error. It will say something like Exception in thread "LWJGL Application" com.badlogic.gdx.utils.GdxRuntimeException: Couldn't load file: badlogic.jpg. If this is the case, the answer is simple.

Go into the run menu at the top of the Android Studio window and click on 'Edit Configurations...' This will open the Run/Debug Configurations Menu. Click on 'DesktopLauncher' from the dropdown menu on the left. Now, on the right side you can see an item called 'Working directory:'. To fix this error just append 'android/assets' to the directory listed. It should look like:

[APPLICATION PATH]/android/assets

This should allow it to run, but if you have another error see below.

"Exception in thread 'main' java.lang.NoClassDefFoundError: com/badlogic/gdx/ApplicationListener"

To solve this problem, we need to run the app as a JAR application. To do this, go into the run menu at the top of the Android Studio window and click on 'Edit Configurations...' This will open the Run/Debug Configurations Menu. In this menu, first click the green plus sign in the top left. Select 'JAR Application' from the drop down menu. You will see something like this:

You need to enter the 'Path to JAR:' which will be:

[APPLICATION PATH]/desktop/build/libs/desktop-1.0.jar

Next, in the 'Before Launch' section at the bottom, hit the green plus and add 'Run Gradle Task'. The 'Gradle Project' should be found at:

[APPLICATION PATH]/desktop/build.gradle

Finally, in the 'Tasks' box, type:

desktop:dist

And that's it. You should be able to run your app on the desktop as a JAR application by clicking the 'Select Run/Debug Configuration' button in the menu and selecting 'JAR Application'. Then just click the green run arrow to the right and wait for it to compile.

HTML:

Let's be honest, libGDX doesn't play well with HTML. But, if you are like me, you want to be a completionist and force it to work. Well, be forewarned: you will have to deal with a lot of code workarounds in order to make your application compile to HTML. For the time being, though, let's just look at how to actually get it to compile.

In Android Studio, open the Gradle window by clicking the vertical 'Gradle' button on the right side. In that menu, expand ':html', then expand 'other', and finally click on 'dist'. That will build your web app.

To find the files, you need to go into:

[APPLICATION PATH]/html/build/dist

All of the files will be in that folder and its subfolders.

A word of warning, though. Even with the default libGDX app (showing a picture on a red background), it doesn't seem to work in every browser. For example, on my Linux machine, it works fine on Seamonkey (2.49.1) but not on Chrome (63.0.3239.132). At some point in the future I might come back to figure out why, but for the time being I am going to accept that it compiles and leave it at that.