revanced-website/docusaurus/docs/development/revanced-patches/5_apis.md

💪 Advanced APIs

ReVanced comes with APIs which assist with the development of patches.

📙 Overview

1. 👹 Create mutable classes with context.proxy(classDef)
2. 🔍 Find mutable classes with BytecodeContext.findClass(predicate)
3. 🏃‍ Walk through the method call hierarchy with BytecodeContext.toMethodWalker(startMethod)
4. 🔨 Work with resources from patches with ResourceUtils
5. 💾 Read and write resources with ResourceContext.get(path)
6. 📃 Edit xml files with DomFileEditor
7. 🔧 Implement settings with app.revanced.patches.shared.settings

🧰 APIs

• 👹 Create mutable classes with context.proxy(classDef)

  To be able to make changes to classes, it is necessary to work on a mutable clone of that class. For that, the BytecodeContext allows to create mutable instances of classes with context.proxy(classDef).

  Example:

  override fun execute(context: BytecodeContext) {   
    // Code
  
    val classProxy = context.proxy(someClass)
  
    // From now on, this class is shadowed over the original class.
    // The original class can still be found in context.classes.
    val proxy = classProxy.mutableClass 
  
    // Code
  
    classProxy.mutableClass.fields.add(someField)
  
    return PatchResultSuccess()
  }
  

  Note

  : The mutable clone will now be used for every future modification on the class, even in other patches, if ClassProxy.mutableClass is accessed. This means, if you try to proxy the same class twice, you will get the same instance of the mutable clone.

  Note

  : On the page 🔎 Fingerprinting the result of fingerprints were introduced. Accessing MethodFingerprint.mutableClass or MutableFingerprint.mutableMethod also creates a mutable clone of the class through a ClassProxy. If you now were to proxy the same class, the fingerprint just proxied, the same mutable clone instance would be used. This also applies for fingerprints, which resolve to the same method.

  Warning

  : Rely on the immutable types as much as possible to avoid creating mutable clones.

  An example on how this api is used can be found in GeneralAdsPatch.

• 🔍 Find mutable classes with BytecodeContext.findClass(predicate)

  This api allows to find classes by a predicate or the class name. It will return a ClassProxy instance by proxying the found class and thus either access the immutable or when necessary, the mutable clone of the class.

  An example on how this api is used can be found in HideCastButtonPatch.