How to pass a parameter to the Java code in run/debug configuration from Android Studio

Question

My android app does some http requests to my server. However sometimes I am debugging the new api code that runs on my development machine. I would like to be able to pass something (like an environment variable) so in my code, if it's present I would be able to use that as the hostname for the api requests from the android emulator.

So I'm looking for a way to pass something like:

API_SERVER=http://10.0.2.2/myapp/

and in my code I would use it somehow, for example:

final static String API_SERVER_REAL = "http://example.com/";
final String apiServerOverride = System.getenv("API_SERVER");
final String API_SERVER = (null != apiServerOverride && !apiServerOverride.isEmpty() ? apiServerOverride : API_SERVER_REAL);

Answer 1

I know this thread is quite old, but in my opinion none of provided answers actually solves the problem. Flavors are ill-suited for parametrizing your build with things like API URLs, and even worse for things like API keys etc.

Firstly, build.gradle which defines flavors is part of project source, therefore it must not contain such information in order to be safely committed into source control systems.

Secondly, a need may arise to test different flavors against different API endpoints/keys. What if you just want to hit some debug http server you just created to solve a bug? Would you create a flavor for that? Probably not... Flavors are good for things like "free flavor" and "premium flavor".

This problem is easily solved using gradles -P flag. You can access gradle properties that are passed this way as regular variables inside your gradle.build, and you can vary it's behavior accordingly.

If you want to push this flags further into your application you can use Scott's solution that was posted here, combined with the provided flag.

The build command would then probably look like:

$ gradle build -Papiroot=http://www.example.com

And in your build.gradle you would define the writeValue task like this:

task writeValue(type:Exec) {
    commandLine '/usr/local/bin/adb', 'shell', "echo 'API_SERVER=${apiroot}' > /data/data/values.properties"
}

FYI the -P flag can be easily configured in Android Studio by navigating from the menu:

Run -> Run/Debug Configurations -> Defaults -> Gradle -> Script Parameters

Answer 2

Probably the simplest thing is to write the data you want to pass to a file on the device in /data/data; your Android app can read the device trivially (perhaps make it a .properties file and use java.util.Properties to read it in). To write it out, use this kind of task in your build.gradle file (and use the correct path to the adb command for your setup):

task writeValue(type:Exec) {
    commandLine '/usr/local/bin/adb', 'shell', 'echo \'API_SERVER=http://10.0.2.2/myapp/\' > /data/data/values.properties'
}

There's documentation on Gradle exec tasks at http://www.gradle.org/docs/current/dsl/org.gradle.api.tasks.Exec.html

You can execute this task manually from Android Studio by using the Gradle tasks view: