rust_for_android_ios_flutter

android.rs

#![cfg(target_os = "android")]
#![allow(non_snake_case)]

use crate::hello;
use jni::objects::{JClass, JString};
use jni::sys::jstring;
use jni::JNIEnv;
use std::ffi::CString;

// NOTE: RustKt references the name rusty.kt, which will be the kotlin file exposing the functions below.
// Remember the JNI naming conventions.

#[no_mangle]
pub extern "system" fn Java_com_robertohuertas_rusty_1android_1lib_RustyKt_helloDirect(
  env: JNIEnv,
  _: JClass,
  input: JString,
) -> jstring {
  let input: String = env
    .get_string(input)
    .expect("Couldn't get Java string!")
    .into();
  let output = env
    .new_string(format!("Hello from Rust: {}", input))
    .expect("Couldn't create a Java string!");
  output.into_inner()
}

#[allow(clippy::similar_names)]
#[no_mangle]
pub extern "system" fn Java_com_robertohuertas_rusty_1android_1lib_RustyKt_hello(
  env: JNIEnv,
  _: JClass,
  input: JString,
) -> jstring {
  let java_str = env.get_string(input).expect("Couldn't get Java string!");
  // we call our generic func for iOS
  let java_str_ptr = java_str.as_ptr();
  let result = unsafe { hello(java_str_ptr) };
  // freeing memory from CString in ios function
  // if we call hello_release we won't have access to the result
  let result_ptr = unsafe { CString::from_raw(result) };
  let result_str = result_ptr.to_str().unwrap();
  let output = env
    .new_string(result_str)
    .expect("Couldn't create a Java string!");
  output.into_inner()
}