make example work on armv7, use JNA to invoke rust instead of JNI

build.gradle

@@ -2,7 +2,7 @@ buildscript {
     Properties versionProperties = new Properties()
     versionProperties.load(new FileInputStream("$project.rootDir/version.properties"))
 
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.6.0'
     ext.agp_version = '4.0.1'
     ext.plugin_version = versionProperties.getProperty("version")
 

samples/app/build.gradle

@@ -1,7 +1,12 @@
 buildscript {
-    ext.agp_version = '7.0.0'
+    //ext.agp_version = '7.0.0'
+    //ext.agp_version = '4.0.1'
+    ext.agp_version = '7.1.1'
     repositories {
         google()
+        //maven {
+        //    url 'file://C:\\Users\\josel\\work\\qaxh3_dev\\fhe-windows\\rust-android-gradle\\plugin\\build\\libs'
+        //}
         maven {
             url "https://plugins.gradle.org/m2/"
         }
@@ -16,13 +21,13 @@ apply plugin: 'com.android.application'
 apply plugin: 'org.mozilla.rust-android-gradle.rust-android'
 
 android {
-    compileSdkVersion 27
-    ndkVersion "23.1.7779620"
+    compileSdkVersion 31
+    ndkVersion "25.2.9519653"
 
     defaultConfig {
         applicationId "com.nishtahir.androidrust"
         minSdkVersion 21
-        targetSdkVersion 27
+        targetSdkVersion 31
         versionCode 1
         versionName "1.0"
         testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
@@ -37,8 +42,12 @@ android {
 
 cargo {
     module = "../rust"
-    targets = ["x86_64", "arm64"]
+    targets = ["x86_64", "arm64", "arm"]
     libname = "rust"
+    pythonCommand = "python"
+    cargoCommand = System.properties['user.home'] + "\\.cargo\\bin\\cargo.exe"
+    rustcCommand = System.properties['user.home'] + "\\.cargo\\bin\\rustc.exe"
+    rustupChannel = "stable"
 }
 
 repositories {
@@ -52,6 +61,7 @@ dependencies {
     })
     implementation 'com.android.support:appcompat-v7:27.1.1'
     implementation 'com.android.support.constraint:constraint-layout:1.0.2'
+    implementation 'net.java.dev.jna:jna:4.4.0@aar'
     testImplementation 'junit:junit:4.12'
 }
 

samples/app/src/main/java/com/nishtahir/androidrust/MainActivity.java

@@ -5,6 +5,9 @@
 import android.util.Log;
 import android.widget.TextView;
 
+import com.sun.jna.Library;
+import com.sun.jna.Native;
+import com.sun.jna.Callback;
 public class MainActivity extends AppCompatActivity implements JNICallback {
 
     private static final String TAG = "MainActivity";
@@ -16,13 +19,20 @@ public class MainActivity extends AppCompatActivity implements JNICallback {
 
     TextView textView;
 
+    private final Callback viaJNA = new Callback() {
+        public void callback(String string) {
+            Log.i("rust","From JNA: " + string);
+            textView.setText("From JNA: " + string);
+        }
+    };
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);
         textView = (TextView) findViewById(R.id.sample_text);
 
         invokeCallbackViaJNI(this);
+        LibService.instance.invokeCallbackViaJNA(viaJNA);
     }
 
     /**
@@ -33,6 +43,15 @@ protected void onCreate(Bundle savedInstanceState) {
 
     @Override
     public void callback(String string) {
+        Log.i("rust","From JNI: " + string);
         textView.append("From JNI: " + string + "\n");
     }
+
 }
+
+interface LibService extends Library {
+    public static final String JNALib = "rust";
+    public static final LibService instance = Native.loadLibrary(JNALib, LibService.class);
+
+    void invokeCallbackViaJNA(Callback callback);
+}

samples/rust/src/lib.rs

@@ -11,7 +11,7 @@ pub type Callback = unsafe extern "C" fn(*const c_char) -> ();
 #[no_mangle]
 #[allow(non_snake_case)]
 pub extern "C" fn invokeCallbackViaJNA(callback: Callback) {
-    let s = CString::new("Hello from Rust").unwrap();
+    let s = CString::new("Hello from Rust JNA").unwrap();
     unsafe { callback(s.as_ptr()); }
 }
 
@@ -22,7 +22,7 @@ pub extern "C" fn Java_com_nishtahir_androidrust_MainActivity_invokeCallbackViaJ
     _class: JClass,
     callback: JObject
 ) {
-    let s = String::from("Hello from Rust");
+    let s = String::from("Hello from Rust JNI");
     let response = env.new_string(&s)
         .expect("Couldn't create java string!");
     env.call_method(callback, "callback", "(Ljava/lang/String;)V",