# 💉 Introduction to ReVanced Patcher
In order to create patches for Android applications, you first need to understand the fundamentals of ReVanced Patcher.
## 📙 How it works
ReVanced Patcher is a library that allows you to modify Android applications by applying patches to their APKs. It is built on top of [Smali](https://github.com/google/smali) for bytecode manipulation and [Androlib (Apktool)](https://github.com/iBotPeaches/Apktool) for resource decoding and encoding.
ReVanced Patcher accepts a list of patches and integrations, and applies them to a given APK file. It then returns the modified components of the APK file, such as modified dex files and resources, that can be repackaged into a new APK file.
ReVanced Patcher has a simple API that allows you to load patches and integrations from JAR files and apply them to an APK file.
Later on, you will learn how to create patches.
```kt
// Executed patches do not necessarily reset their state.
// For that reason it is important to create a new instance of the PatchBundleLoader
// once the patches are executed instead of reusing the same instance of patches loaded by PatchBundleLoader.
val patches: PatchSet /* = Set> */ = PatchBundleLoader.Jar(File("revanced-patches.jar"))
val integrations = setOf(File("integrations.apk"))
// Instantiating the patcher will decode the manifest of the APK file to read the package and version name.
val patcherConfig = PatcherConfig(apkFile = File("some.apk"))
val patcherResult = Patcher(patcherConfig).use { patcher ->
patcher.apply {
acceptIntegrations(integrations)
acceptPatches(patches)
// Execute patches.
runBlocking {
patcher.apply(returnOnError = false).collect { patchResult ->
if (patchResult.exception != null)
println("${patchResult.patchName} failed:\n${patchResult.exception}")
else
println("${patchResult.patchName} succeeded")
}
}
}.get()
}
// The result of the patcher contains the modified components of the APK file that can be repackaged into a new APK file.
val dexFiles = patcherResult.dexFiles
val resources = patcherResult.resources
```
## ⏭️ What's next
The next page teaches the fundamentals of ReVanced Patches.
Continue: [🧩 Introduction to ReVanced Patches](2_patches_intro.md)
