patch support library using Android Studio

问题:

I've moved my project to Android Studio a month ago, and I'm glad I did, despite the need to switch to a new (and more powerful) build system (gradle). One thing I'd have known in Eclipse, but I can't figure out how to achieve now, is patching the support library. I know that it does not sound like a good practice, but a couple of code lines are driving me crazy, and the solution would be to simply modify it to solve my problem.
I've tried to modify the code in the sdk's ".\extras\android\m2repository\com\android\support" directory, but that does not seem to affect the code that is really used for compilation.
Any idea about how to achieve this ?

Edit:

I tried to create a module "SupportLibraryV4" in my project, and this is what gradle tells me when I try to build it :

Error Code:
    1
Output:

    trouble processing "java/android/support/v4/R$anim.class":

    Ill-advised or mistaken usage of a core class (java.* or javax.*)
    when not building a core library.

    This is often due to inadvertently including a core library file
    in your application's project, when using an IDE (such as
    Eclipse). If you are sure you're not intentionally defining a
    core class, then this is the most likely explanation of what's
    going on.

    However, you might actually be trying to define a class in a core
    namespace, the source of which you may have taken, for example,
    from a non-Android virtual machine project. This will most
    assuredly not work. At a minimum, it jeopardizes the
    compatibility of your app with future versions of the platform.
    It is also often of questionable legality.

    If you really intend to build a core library -- which is only
    appropriate as part of creating a full virtual machine
    distribution, as opposed to compiling an application -- then use
    the "--core-library" option to suppress this error message.

    If you go ahead and use "--core-library" but are in fact
    building an application, then be forewarned that your application
    will still fail to build or run, at some point. Please be
    prepared for angry customers who find, for example, that your
    application ceases to function once they upgrade their operating
    system. You will be to blame for this problem.

    If you are legitimately using some code that happens to be in a
    core package, then the easiest safe alternative you have is to
    repackage that code. That is, move the classes in question into
    your own package namespace. This means that they will never be in
    conflict with core system classes. JarJar is a tool that may help
    you in this endeavor. If you find that you cannot do this, then
    that is an indication that the path you are on will ultimately
    lead to pain, suffering, grief, and lamentation.

    1 error; aborting

impressive !

回答1:

Android sdk doesn't have all required files for building support library. You need to checkout additional repositories from https://android.googlesource.com:

• platform/frameworks/support
• platform/prebuilts/gradle-plugin
• platform/prebuilts/maven_repo/android
• platform/prebuilts/sdk
• platform/prebuilts/tools

Please, keep the directory structure as in android repository.

Now you could change any code in support library. If you need to change support library for api v.4 do it in "platform\frameworks\support\v4". For building patched version of support library use gradle with next command:

platform\frameworks\support\v4\gradle clean jar

Resulted jar could be found in "platform\out\host\gradle\frameworks\support\v4\libs\". Put it to the libs folder of your project and add in build.gradle file.

回答2:

Updated answer 2016 for Linux and OS X using the bundled gradle wrapper instead of the system's gradle installation:

Checkout the following repositories from https://android.googlesource.com and keep the directory structure:

• platform/frameworks/support
• platform/prebuilts/gradle-plugin
• platform/prebuilts/maven_repo/android
• platform/prebuilts/sdk
• platform/prebuilts/tools
• platform/tools/external/gradle

Modify files in the library:

• Change files in platform/frameworks/support/

Build AAR

• cd platform/frameworks/support
• ./gradlew jarRelease
• The resulting .aar is in platform/out/host/gradle/frameworks/support/<module>/build/outputs/aar/

Add to project

• Create a libs/ folder next to your app's build.gradle
• Add libs folder to build.gradle: repositories{ flatDir{ dirs 'libs' } }
• Copy the .aar file to libs/
• Add aar to your dependencies section in build.gradle, e.g.: dependencies { compile(name:'my_custom_supportlib_module', ext:'aar') }

Module already in project

When you patches a support library module that other modules depend on, you'll have it twice in the build causing errors. This can be avoided by excluding the original dependency.

If you for example patch recyclerview-v7 and add

dependencies {
    compile(name:'recyclerview-v7-release', ext:'aar')
}

you have to exclude the dependency like this. Change

compile "com.android.support:design:24.2.1"

to

compile("com.android.support:design:24.2.1") {
    exclude group: 'com.android.support', module: 'recyclerview-v7'
}

for all modules that depend on the patched module.

回答3:

Patch the SupportLib and add it manually as a jar:

• Put the SupportLib jar into the libs folder
• Right click it and hit 'Add as library'
• Ensure that compile files('libs/supportlib.jar') is in your build.gradle file
• Do a clean build

Disclaimer: Android Studio: Add jar as library?

回答4:

Turns out that Ilya Tretyakov's answer only works for parts of the support library that don't have resources because they can't be put into a .jar.

The correct way to build for example the design-support-library is as follows:

checkout these repos from https://android.googlesource.com and keep the file structure:

• platform/frameworks/support
• platform/prebuilts/gradle-plugin
• platform/prebuilts/maven_repo/android
• platform/prebuilts/sdk
• platform/prebuilts/tools

navigate to platform/frameworks/support/design and edit whatever file you want. Now rebuild everything with gradle clean assembleRelease

you can find the resulting library file support-design-release.aar in platform/out/host/gradle/frameworks/support/support-design/build/outputs/aar

create an app/libs folder in your project and edit the app/build.gradle:

repositories{
   flatDir{
      dirs 'libs'
   }
}

dependencies {
   compile(name:'support-design-release.aar', ext:'aar')
}

do a clean rebuild of your project and everything will work as intended