revanced-patcher/docs/4_apis.md

💪 Advanced APIs

A handful of APIs are available to make patch development easier and more efficient.

📙 Overview

1. 👹 Create mutable replacements of classes with proxy(ClassDef)
2. 🔍 Find and create mutable replaces with classBy(Predicate)
3. 🏃‍ Navigate method calls recursively by index with navigate(Method)
4. 💾 Read and write resource files with get(String, Boolean) and delete(String)
5. 📃 Read and write DOM files using document(String) and document(InputStream)

🧰 APIs

👹 proxy(ClassDef)

By default, the classes are immutable, meaning they cannot be modified. To make a class mutable, use the proxy(ClassDef) function. This function creates a lazy mutable copy of the class definition. Accessing the property will replace the original class definition with the mutable copy, thus allowing you to make changes to the class. Subsequent accesses will return the same mutable copy.

execute {
    val mutableClass = proxy(classDef)
    mutableClass.methods.add(Method())
}

🔍 classBy(Predicate)

The classBy(Predicate) function is an alternative to finding and creating mutable classes by a predicate. It automatically proxies the class definition, making it mutable.

execute {
    // Alternative to proxy(classes.find { it.name == "Lcom/example/MyClass;" })?.classDef
    val classDef = classBy { it.name == "Lcom/example/MyClass;" }?.classDef
}

🏃‍ navigate(Method).at(index)

The navigate(Method) function allows you to navigate method calls recursively by index.

execute {
    // Sequentially navigate to the instructions at index 1 within 'someMethod'.
    val method = navigate(someMethod).to(1).original() // original() returns the original immutable method.
    
    // Further navigate to the second occurrence where the instruction's opcode is 'INVOKEVIRTUAL'.
    // stop() returns the mutable copy of the method.
    val method = navigate(someMethod).to(2) { instruction -> instruction.opcode == Opcode.INVOKEVIRTUAL }.stop()
    
    // Alternatively, to stop(), you can delegate the method to a variable.
    val method by navigate(someMethod).to(1)
    
    // You can chain multiple calls to at() to navigate deeper into the method.
    val method by navigate(someMethod).to(1).to(2, 3, 4).to(5)
}

💾 get(String, Boolean) and delete(String)

The get(String, Boolean) function returns a File object that can be used to read and write resource files.

execute {
    val file = get("res/values/strings.xml")
    val content = file.readText()
    file.writeText(content)
}

The delete function can mark files for deletion when the APK is rebuilt.

execute {
    delete("res/values/strings.xml")
}

📃 document(String) and document(InputStream)

The document function is used to read and write DOM files.

execute {
    document("res/values/strings.xml").use { document ->
        val element = doc.createElement("string").apply {
            textContent = "Hello, World!"
        }
        document.documentElement.appendChild(element)
    }
}

You can also read documents from an InputStream:

execute {
    val inputStream = classLoader.getResourceAsStream("some.xml")
    document(inputStream).use { document ->
        // ...
    }
}

🎉 Afterword

ReVanced Patcher is a powerful library to patch Android applications, offering a rich set of APIs to develop patches that outlive app updates. Patches make up ReVanced; without you, the community of patch developers, ReVanced would not be what it is today. We hope that this documentation has been helpful to you and are excited to see what you will create with ReVanced Patcher. If you have any questions or need help, talk to us on one of our platforms linked on revanced.app or open an issue in case of a bug or feature request,
ReVanced