feat: Add Android build support

README.md

@@ -69,7 +69,7 @@ Cashu is an ecash protocol that enables Bitcoin transactions with maximum privac
 ## 🔧 Technologies
 
 ### Frontend
-- **Flutter 3.3+**: Cross-platform framework
+- **Flutter 3.27+**: Cross-platform framework
 - **Dart**: Programming language
 - **Provider**: State management
 - **QR Flutter**: QR code generation
@@ -90,10 +90,11 @@ Cashu is an ecash protocol that enables Bitcoin transactions with maximum privac
 
 ### Prerequisites
 
-- Flutter SDK (>=3.3.0)
-- Dart SDK
-- Android Studio / Xcode (for native builds)
-- Rust toolchain (to compile cdk-flutter)
+- Flutter SDK (>=3.27.0)
+- Dart SDK (>=3.6.0)
+- Android Studio with Android SDK
+- Android NDK 26.3+ (install via Android Studio > SDK Manager > SDK Tools)
+- Rust toolchain (>=1.85.0)
 
 ### Clone the Repository
 
@@ -108,19 +109,74 @@ cd elcaju
 flutter pub get
 ```
 
-### Configure Rust (Ubuntu/Linux)
+### Configure Rust for Android (Linux/macOS)
 
 ```bash
-# Install Android targets
-rustup target add armv7-linux-androideabi
-rustup target add aarch64-linux-android
-rustup target add i686-linux-android
-rustup target add x86_64-linux-android
+# Install Rust if not already installed
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
 
-# Create ~/.cargo/config.toml
+# Update to latest stable (requires >= 1.85.0)
+rustup update stable
+
+# Install Android targets
+rustup target add aarch64-linux-android   # arm64-v8a (modern devices)
+rustup target add armv7-linux-androideabi # armeabi-v7a (older devices)
+rustup target add x86_64-linux-android    # x86_64 (emulators)
+```
+
+### Configure Android NDK Linkers
+
+Create or edit `~/.cargo/config.toml` with your NDK path:
+
+```toml
 [target.x86_64-unknown-linux-gnu]
 linker = "gcc"
 rustflags = ["-C", "link-arg=-fuse-ld=bfd"]
+
+[target.aarch64-linux-android]
+linker = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android24-clang"
+
+[target.armv7-linux-androideabi]
+linker = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/armv7a-linux-androideabi24-clang"
+
+[target.x86_64-linux-android]
+linker = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android24-clang"
+
+[env]
+CC_armv7-linux-androideabi = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/armv7a-linux-androideabi24-clang"
+AR_armv7-linux-androideabi = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar"
+CC_x86_64-linux-android = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/x86_64-linux-android24-clang"
+AR_x86_64-linux-android = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar"
+CC_aarch64-linux-android = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android24-clang"
+AR_aarch64-linux-android = "/path/to/Android/Sdk/ndk/26.3.11579264/toolchains/llvm/prebuilt/linux-x86_64/bin/llvm-ar"
+```
+
+> **Note**: Replace `/path/to/Android/Sdk` with your actual Android SDK path (usually `~/Android/Sdk` on Linux or `~/Library/Android/sdk` on macOS).
+
+### Compile Native Libraries
+
+The cdk_flutter native libraries must be compiled manually:
+
+```bash
+# Navigate to cdk_flutter rust directory
+cd ~/.pub-cache/git/cdk_flutter-*/rust
+
+# Build for each architecture
+cargo build --release --target aarch64-linux-android
+cargo build --release --target armv7-linux-androideabi
+cargo build --release --target x86_64-linux-android
+
+# Copy libraries to project
+mkdir -p /path/to/elcaju/android/app/src/main/jniLibs/{arm64-v8a,armeabi-v7a,x86_64}
+
+cp target/aarch64-linux-android/release/libcdk_flutter.so \
+   /path/to/elcaju/android/app/src/main/jniLibs/arm64-v8a/
+
+cp target/armv7-linux-androideabi/release/libcdk_flutter.so \
+   /path/to/elcaju/android/app/src/main/jniLibs/armeabi-v7a/
+
+cp target/x86_64-linux-android/release/libcdk_flutter.so \
+   /path/to/elcaju/android/app/src/main/jniLibs/x86_64/
 ```
 
 ### Run in Development
@@ -132,13 +188,29 @@ flutter run
 ### Build for Production
 
 ```bash
-# Android APK
+# Android APK (includes all architectures, ~55MB)
 flutter build apk --release
 
-# Android App Bundle
+# Android App Bundle (recommended for Play Store)
 flutter build appbundle --release
 ```
 
+### Quick Build (arm64 only)
+
+For faster builds targeting only modern devices:
+
+```bash
+# Build only arm64 library
+cargo build --release --target aarch64-linux-android
+
+# Copy to project
+cp target/aarch64-linux-android/release/libcdk_flutter.so \
+   android/app/src/main/jniLibs/arm64-v8a/
+
+# Build APK (~40MB)
+flutter build apk --release
+```
+
 ---
 
 ## 🏗️ Architecture

android/app/build.gradle

@@ -0,0 +1,41 @@
+plugins {
+    id "com.android.application"
+    id "kotlin-android"
+    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
+    id "dev.flutter.flutter-gradle-plugin"
+}
+
+android {
+    namespace "me.elcaju"
+    compileSdk flutter.compileSdkVersion
+    ndkVersion "27.0.12077973"
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_11
+        targetCompatibility JavaVersion.VERSION_11
+    }
+
+    kotlinOptions {
+        jvmTarget = JavaVersion.VERSION_11.toString()
+    }
+
+    defaultConfig {
+        applicationId "me.elcaju"
+        minSdk flutter.minSdkVersion
+        targetSdk flutter.targetSdkVersion
+        versionCode flutter.versionCode
+        versionName flutter.versionName
+    }
+
+    buildTypes {
+        release {
+            // TODO: Add your own signing config for the release build.
+            // Signing with the debug keys for now, so `flutter run --release` works.
+            signingConfig signingConfigs.debug
+        }
+    }
+}
+
+flutter {
+    source "../.."
+}

android/app/build.gradle.kts

@@ -1,43 +0,0 @@
-plugins {
-    id("com.android.application")
-    id("kotlin-android")
-    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
-    id("dev.flutter.flutter-gradle-plugin")
-}
-
-android {
-    namespace = "me.elcaju"
-    compileSdk = flutter.compileSdkVersion
-    ndkVersion = "27.0.12077973"
-
-    compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_11
-        targetCompatibility = JavaVersion.VERSION_11
-    }
-
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_11.toString()
-    }
-
-    defaultConfig {
-        applicationId = "me.elcaju"
-        // You can update the following values to match your application needs.
-        // For more information, see: https://flutter.dev/to/review-gradle-config.
-        minSdk = flutter.minSdkVersion
-        targetSdk = flutter.targetSdkVersion
-        versionCode = flutter.versionCode
-        versionName = flutter.versionName
-    }
-
-    buildTypes {
-        release {
-            // TODO: Add your own signing config for the release build.
-            // Signing with the debug keys for now, so `flutter run --release` works.
-            signingConfig = signingConfigs.getByName("debug")
-        }
-    }
-}
-
-flutter {
-    source = "../.."
-}

android/app/src/main/AndroidManifest.xml

@@ -1,4 +1,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <!-- Permisos de red requeridos para conectar con mints Cashu -->
+    <uses-permission android:name="android.permission.INTERNET"/>
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>
+
     <application
         android:label="ElCaju"
         android:name="${applicationName}"

android/build.gradle

@@ -5,17 +5,18 @@ allprojects {
     }
 }
 
-val newBuildDir: Directory = rootProject.layout.buildDirectory.dir("../../build").get()
+def newBuildDir = rootProject.layout.buildDirectory.dir("../../build").get()
 rootProject.layout.buildDirectory.value(newBuildDir)
 
 subprojects {
-    val newSubprojectBuildDir: Directory = newBuildDir.dir(project.name)
+    def newSubprojectBuildDir = newBuildDir.dir(project.name)
     project.layout.buildDirectory.value(newSubprojectBuildDir)
 }
+
 subprojects {
     project.evaluationDependsOn(":app")
 }
 
-tasks.register<Delete>("clean") {
-    delete(rootProject.layout.buildDirectory)
+tasks.register("clean", Delete) {
+    delete rootProject.layout.buildDirectory
 }

android/settings.gradle

@@ -0,0 +1,25 @@
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        file("local.properties").withInputStream { properties.load(it) }
+        def flutterSdkPath = properties.getProperty("flutter.sdk")
+        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+        return flutterSdkPath
+    }()
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
+    id "com.android.application" version "8.7.3" apply false
+    id "org.jetbrains.kotlin.android" version "2.1.0" apply false
+}
+
+include ":app"

android/settings.gradle.kts

@@ -1,25 +0,0 @@
-pluginManagement {
-    val flutterSdkPath = run {
-        val properties = java.util.Properties()
-        file("local.properties").inputStream().use { properties.load(it) }
-        val flutterSdkPath = properties.getProperty("flutter.sdk")
-        require(flutterSdkPath != null) { "flutter.sdk not set in local.properties" }
-        flutterSdkPath
-    }
-
-    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
-
-    repositories {
-        google()
-        mavenCentral()
-        gradlePluginPortal()
-    }
-}
-
-plugins {
-    id("dev.flutter.flutter-plugin-loader") version "1.0.0"
-    id("com.android.application") version "8.7.3" apply false
-    id("org.jetbrains.kotlin.android") version "2.1.0" apply false
-}
-
-include(":app")