Android Gradle dependencies - only Maven? - maven

Question

I'm trying to get to know the Android Studio / Gradle build system, having come from Eclipse and Ant. In particular, I don't understand how the dependencies block in my build.gradle file works.
My current project has the following structure:
In my project I am using both the android support library (v4), and the jxl spreadsheet library. My build.gradle (the one inside the sub-module, not the root level one) currently looks like this:
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath 'com.android.tools.build:gradle:0.6.+'
}
}
apply plugin: 'android'
repositories {
mavenCentral()
}
android {
compileSdkVersion 18
buildToolsVersion "18.1.1"
defaultConfig {
minSdkVersion 14
targetSdkVersion 19
}
buildTypes {
release {
runProguard true
proguardFile getDefaultProguardFile('proguard-android-optimize.txt')
}
}
productFlavors {
defaultFlavor {
proguardFile 'proguard-rules.txt'
}
}
}
dependencies {
compile 'net.sourceforge.jexcelapi:jxl:2.6.+'
compile 'com.android.support:support-v4:13.0.+'
//compile fileTree(dir: 'libs', include: '*.jar')
}
On the second last line, you can see I've tried using the local copies of android-support-v4.jar and jxl.jar. I've also tried using the lines
compile files('libs/android-support-v4.jar')
compile files('libs/jxl.jar')
However, whenever I try to use the local .jar files, my build fails, saying that the Android support and jxl libraries cannot be found. I've seen lots of posts saying that you can simply use local .jars like this, however I cannot get this to work. If possible, I would like to be able to use my locally stored .jar files so I can work offline, when Maven isn't available.
Can anyone tell me why using the local .jar files doesn't work?
EDIT: I've also tried restarting the Android Studio IDE, and cleaning and re-building my project after adding the local jar dependency lines.

Answer 1

It's not finding the libs directory because it needs to be located at your module root instead of inside src/main. The paths in build.gradle are relative to the location of the build.gradle file, which lives in your module root.
For the Android support library, I'd recommend using the Maven dependency (e.g. compile 'com.android.support:support-v4:13.0.+') instead of including the jar file. With the support library, the Android Gradle plugin actually looks for it in your SDK instead of going out to the network for it; you have to have the support repository installed via the SDK manager. This is actually a little confusing and trips up a lot of users since it's not well-documented. But if you access it this way instead of just including the JAR, then the build system can be smarter about not trying to include duplicate copies of it and causing errors if you include other library projects that depend on it.