如何借助Java/Kotlin将R语言脚本/程序转换为Android应用，或在Android应用中通过Java/Kotlin执行R脚本？

Hey there! Let's break down your questions step by step since you're building an Android app and want to work with R alongside Java/Kotlin.

There are a few solid ways to execute R code directly in your Android app, depending on your needs:

• Renjin Library (Recommended for Simple Use Cases)
  Renjin is a pure-Java implementation of the R engine, which makes it super straightforward to drop into an Android project without dealing with messy native code. Here's how to set it up:

  1. Add the dependency to your module-level build.gradle file:

     implementation 'org.renjin:renjin-script-engine:3.5.0'
     

  2. Call R code from Kotlin/Java:
     Example Kotlin snippet:

     import org.renjin.script.RenjinScriptEngine
     import javax.script.ScriptEngineManager
     
     fun executeRScript() {
         val engineManager = ScriptEngineManager()
         val renjinEngine = engineManager.getEngineByName("Renjin") as? RenjinScriptEngine
         
         renjinEngine?.runCatching {
             // Execute your R code here
             val calculationResult = eval("data <- c(1,3,5,7,9); median(data)")
             // Use the result in your Android UI, e.g., update a TextView
             println("Median value: $calculationResult")
         }?.onFailure {
             it.printStackTrace()
             // Handle errors like unsupported R functions/packages
         }
     }
     

     Note: Renjin doesn't support every single R package out there, so double-check if your script relies on niche libraries before going all-in.

• R for Android + JNI (For Full R Environment)
  If you need access to the complete R ecosystem (including all packages), you can use the precompiled R for Android libraries and call them via JNI. This is more complex—you'll need to set up the Android NDK, link the R native libraries, and write JNI bridges to connect Java/Kotlin to R functions. It's great for heavy-duty R workloads but has a steeper learning curve.

• Web-Based Workaround
  If your R script is complex or relies on unsupported packages, consider hosting it on a backend server (use R's Plumber package to turn it into an API). Then, your Android app can send HTTP requests to the server, get the computed results, and display them locally. No R integration needed on the device, but you'll need a stable network connection.

There's no one-click tool to "convert" an R script into an Android app, but you can wrap your R logic into an Android app using the integration methods above:

• First, isolate the core functionality of your R script (e.g., statistical calculations, data processing).
• Pick an integration method (Renjin is ideal for most cases) and embed the R code into your Android app's business logic.
• Build an Android UI around it—add buttons to trigger R execution, TextViews to display results, or charts to visualize output.
• Test thoroughly to ensure compatibility with Android's lifecycle and device constraints (like memory limits).

Directly converting R code to readable Java/Kotlin is tricky because the two languages have very different paradigms (R is dynamic/functional; Java/Kotlin are static/object-oriented). That said, here are your options:

• Renjin Bytecode Compilation
  Renjin can compile R code into Java bytecode, which runs on the JVM (and thus Android). You won't get human-readable Java/Kotlin code, but you can call the compiled logic via Renjin's API. It's a way to run R code efficiently without interpreting it on the fly.

• Manual Translation (Most Reliable)
  For simple R scripts, manually rewrite the logic in Java/Kotlin using equivalent libraries:

  • Basic stats: Use Kotlin's built-in functions like average(), sum(), or libraries like Apache Commons Math.
  • Machine learning: Look for Java/Kotlin ports of R libraries (e.g., Smile for ML models).
    This approach gives you full control over performance and compatibility, though it takes more time.

• r2java (Limited Use)
  There's a tool called r2java that can convert basic R code to Java, but it's outdated and only supports simple syntax/functions. It's not recommended for complex scripts, but it might save you a few minutes for trivial calculations.

内容的提问来源于stack exchange，提问作者Nouman Rasheed