init

build/android/app/src/main/AndroidManifest.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools">
+
+    <!-- Internet permission for WebView -->
+    <uses-permission android:name="android.permission.INTERNET" />
+
+    <application
+        android:allowBackup="true"
+        android:icon="@mipmap/ic_launcher"
+        android:label="@string/app_name"
+        android:roundIcon="@mipmap/ic_launcher_round"
+        android:supportsRtl="true"
+        android:theme="@style/Theme.WailsApp"
+        android:usesCleartextTraffic="true"
+        tools:targetApi="31">
+
+        <activity
+            android:name=".MainActivity"
+            android:exported="true"
+            android:configChanges="orientation|screenSize|keyboardHidden"
+            android:windowSoftInputMode="adjustResize">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN" />
+                <category android:name="android.intent.category.LAUNCHER" />
+            </intent-filter>
+        </activity>
+    </application>
+
+</manifest>

build/android/app/src/main/java/com/wails/app/MainActivity.java

@@ -0,0 +1,198 @@
+package com.wails.app;
+
+import android.annotation.SuppressLint;
+import android.os.Bundle;
+import android.util.Log;
+import android.webkit.WebResourceRequest;
+import android.webkit.WebResourceResponse;
+import android.webkit.WebSettings;
+import android.webkit.WebView;
+import android.webkit.WebViewClient;
+
+import androidx.annotation.Nullable;
+import androidx.appcompat.app.AppCompatActivity;
+import androidx.webkit.WebViewAssetLoader;
+import com.wails.app.BuildConfig;
+
+/**
+ * MainActivity hosts the WebView and manages the Wails application lifecycle.
+ * It uses WebViewAssetLoader to serve assets from the Go library without
+ * requiring a network server.
+ */
+public class MainActivity extends AppCompatActivity {
+    private static final String TAG = "WailsActivity";
+    private static final String WAILS_SCHEME = "https";
+    private static final String WAILS_HOST = "wails.localhost";
+
+    private WebView webView;
+    private WailsBridge bridge;
+    private WebViewAssetLoader assetLoader;
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+
+        // Initialize the native Go library
+        bridge = new WailsBridge(this);
+        bridge.initialize();
+
+        // Set up WebView
+        setupWebView();
+
+        // Load the application
+        loadApplication();
+    }
+
+    @SuppressLint("SetJavaScriptEnabled")
+    private void setupWebView() {
+        webView = findViewById(R.id.webview);
+
+        // Configure WebView settings
+        WebSettings settings = webView.getSettings();
+        settings.setJavaScriptEnabled(true);
+        settings.setDomStorageEnabled(true);
+        settings.setDatabaseEnabled(true);
+        settings.setAllowFileAccess(false);
+        settings.setAllowContentAccess(false);
+        settings.setMediaPlaybackRequiresUserGesture(false);
+        settings.setMixedContentMode(WebSettings.MIXED_CONTENT_NEVER_ALLOW);
+
+        // Enable debugging in debug builds
+        if (BuildConfig.DEBUG) {
+            WebView.setWebContentsDebuggingEnabled(true);
+        }
+
+        // Set up asset loader for serving local assets
+        assetLoader = new WebViewAssetLoader.Builder()
+                .setDomain(WAILS_HOST)
+                .addPathHandler("/", new WailsPathHandler(bridge))
+                .build();
+
+        // Set up WebView client to intercept requests
+        webView.setWebViewClient(new WebViewClient() {
+            @Nullable
+            @Override
+            public WebResourceResponse shouldInterceptRequest(WebView view, WebResourceRequest request) {
+                String url = request.getUrl().toString();
+                Log.d(TAG, "Intercepting request: " + url);
+
+                // Handle wails.localhost requests
+                if (request.getUrl().getHost() != null &&
+                        request.getUrl().getHost().equals(WAILS_HOST)) {
+
+                    // For wails API calls (runtime, capabilities, etc.), we need to pass the full URL
+                    // including query string because WebViewAssetLoader.PathHandler strips query params
+                    String path = request.getUrl().getPath();
+                    if (path != null && path.startsWith("/wails/")) {
+                        // Get full path with query string for runtime calls
+                        String fullPath = path;
+                        String query = request.getUrl().getQuery();
+                        if (query != null && !query.isEmpty()) {
+                            fullPath = path + "?" + query;
+                        }
+                        Log.d(TAG, "Wails API call detected, full path: " + fullPath);
+
+                        // Call bridge directly with full path
+                        byte[] data = bridge.serveAsset(fullPath, request.getMethod(), "{}");
+                        if (data != null && data.length > 0) {
+                            java.io.InputStream inputStream = new java.io.ByteArrayInputStream(data);
+                            java.util.Map<String, String> headers = new java.util.HashMap<>();
+                            headers.put("Access-Control-Allow-Origin", "*");
+                            headers.put("Cache-Control", "no-cache");
+                            headers.put("Content-Type", "application/json");
+
+                            return new WebResourceResponse(
+                                "application/json",
+                                "UTF-8",
+                                200,
+                                "OK",
+                                headers,
+                                inputStream
+                            );
+                        }
+                        // Return error response if data is null
+                        return new WebResourceResponse(
+                            "application/json",
+                            "UTF-8",
+                            500,
+                            "Internal Error",
+                            new java.util.HashMap<>(),
+                            new java.io.ByteArrayInputStream("{}".getBytes())
+                        );
+                    }
+
+                    // For regular assets, use the asset loader
+                    return assetLoader.shouldInterceptRequest(request.getUrl());
+                }
+
+                return super.shouldInterceptRequest(view, request);
+            }
+
+            @Override
+            public void onPageFinished(WebView view, String url) {
+                super.onPageFinished(view, url);
+                Log.d(TAG, "Page loaded: " + url);
+                // Inject Wails runtime
+                bridge.injectRuntime(webView, url);
+            }
+        });
+
+        // Add JavaScript interface for Go communication
+        webView.addJavascriptInterface(new WailsJSBridge(bridge, webView), "wails");
+    }
+
+    private void loadApplication() {
+        // Load the main page from the asset server
+        String url = WAILS_SCHEME + "://" + WAILS_HOST + "/";
+        Log.d(TAG, "Loading URL: " + url);
+        webView.loadUrl(url);
+    }
+
+    /**
+     * Execute JavaScript in the WebView from the Go side
+     */
+    public void executeJavaScript(final String js) {
+        runOnUiThread(() -> {
+            if (webView != null) {
+                webView.evaluateJavascript(js, null);
+            }
+        });
+    }
+
+    @Override
+    protected void onResume() {
+        super.onResume();
+        if (bridge != null) {
+            bridge.onResume();
+        }
+    }
+
+    @Override
+    protected void onPause() {
+        super.onPause();
+        if (bridge != null) {
+            bridge.onPause();
+        }
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+        if (bridge != null) {
+            bridge.shutdown();
+        }
+        if (webView != null) {
+            webView.destroy();
+        }
+    }
+
+    @Override
+    public void onBackPressed() {
+        if (webView != null && webView.canGoBack()) {
+            webView.goBack();
+        } else {
+            super.onBackPressed();
+        }
+    }
+}

build/android/app/src/main/java/com/wails/app/WailsBridge.java

@@ -0,0 +1,214 @@
+package com.wails.app;
+
+import android.content.Context;
+import android.util.Log;
+import android.webkit.WebView;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * WailsBridge manages the connection between the Java/Android side and the Go native library.
+ * It handles:
+ * - Loading and initializing the native Go library
+ * - Serving asset requests from Go
+ * - Passing messages between JavaScript and Go
+ * - Managing callbacks for async operations
+ */
+public class WailsBridge {
+    private static final String TAG = "WailsBridge";
+
+    static {
+        // Load the native Go library
+        System.loadLibrary("wails");
+    }
+
+    private final Context context;
+    private final AtomicInteger callbackIdGenerator = new AtomicInteger(0);
+    private final ConcurrentHashMap<Integer, AssetCallback> pendingAssetCallbacks = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<Integer, MessageCallback> pendingMessageCallbacks = new ConcurrentHashMap<>();
+    private WebView webView;
+    private volatile boolean initialized = false;
+
+    // Native methods - implemented in Go
+    private static native void nativeInit(WailsBridge bridge);
+    private static native void nativeShutdown();
+    private static native void nativeOnResume();
+    private static native void nativeOnPause();
+    private static native void nativeOnPageFinished(String url);
+    private static native byte[] nativeServeAsset(String path, String method, String headers);
+    private static native String nativeHandleMessage(String message);
+    private static native String nativeGetAssetMimeType(String path);
+
+    public WailsBridge(Context context) {
+        this.context = context;
+    }
+
+    /**
+     * Initialize the native Go library
+     */
+    public void initialize() {
+        if (initialized) {
+            return;
+        }
+
+        Log.i(TAG, "Initializing Wails bridge...");
+        try {
+            nativeInit(this);
+            initialized = true;
+            Log.i(TAG, "Wails bridge initialized successfully");
+        } catch (Exception e) {
+            Log.e(TAG, "Failed to initialize Wails bridge", e);
+        }
+    }
+
+    /**
+     * Shutdown the native Go library
+     */
+    public void shutdown() {
+        if (!initialized) {
+            return;
+        }
+
+        Log.i(TAG, "Shutting down Wails bridge...");
+        try {
+            nativeShutdown();
+            initialized = false;
+        } catch (Exception e) {
+            Log.e(TAG, "Error during shutdown", e);
+        }
+    }
+
+    /**
+     * Called when the activity resumes
+     */
+    public void onResume() {
+        if (initialized) {
+            nativeOnResume();
+        }
+    }
+
+    /**
+     * Called when the activity pauses
+     */
+    public void onPause() {
+        if (initialized) {
+            nativeOnPause();
+        }
+    }
+
+    /**
+     * Serve an asset from the Go asset server
+     * @param path The URL path requested
+     * @param method The HTTP method
+     * @param headers The request headers as JSON
+     * @return The asset data, or null if not found
+     */
+    public byte[] serveAsset(String path, String method, String headers) {
+        if (!initialized) {
+            Log.w(TAG, "Bridge not initialized, cannot serve asset: " + path);
+            return null;
+        }
+
+        Log.d(TAG, "Serving asset: " + path);
+        try {
+            return nativeServeAsset(path, method, headers);
+        } catch (Exception e) {
+            Log.e(TAG, "Error serving asset: " + path, e);
+            return null;
+        }
+    }
+
+    /**
+     * Get the MIME type for an asset
+     * @param path The asset path
+     * @return The MIME type string
+     */
+    public String getAssetMimeType(String path) {
+        if (!initialized) {
+            return "application/octet-stream";
+        }
+
+        try {
+            String mimeType = nativeGetAssetMimeType(path);
+            return mimeType != null ? mimeType : "application/octet-stream";
+        } catch (Exception e) {
+            Log.e(TAG, "Error getting MIME type for: " + path, e);
+            return "application/octet-stream";
+        }
+    }
+
+    /**
+     * Handle a message from JavaScript
+     * @param message The message from JavaScript (JSON)
+     * @return The response to send back to JavaScript (JSON)
+     */
+    public String handleMessage(String message) {
+        if (!initialized) {
+            Log.w(TAG, "Bridge not initialized, cannot handle message");
+            return "{\"error\":\"Bridge not initialized\"}";
+        }
+
+        Log.d(TAG, "Handling message from JS: " + message);
+        try {
+            return nativeHandleMessage(message);
+        } catch (Exception e) {
+            Log.e(TAG, "Error handling message", e);
+            return "{\"error\":\"" + e.getMessage() + "\"}";
+        }
+    }
+
+    /**
+     * Inject the Wails runtime JavaScript into the WebView.
+     * Called when the page finishes loading.
+     * @param webView The WebView to inject into
+     * @param url The URL that finished loading
+     */
+    public void injectRuntime(WebView webView, String url) {
+        this.webView = webView;
+        // Notify Go side that page has finished loading so it can inject the runtime
+        Log.d(TAG, "Page finished loading: " + url + ", notifying Go side");
+        if (initialized) {
+            nativeOnPageFinished(url);
+        }
+    }
+
+    /**
+     * Execute JavaScript in the WebView (called from Go side)
+     * @param js The JavaScript code to execute
+     */
+    public void executeJavaScript(String js) {
+        if (webView != null) {
+            webView.post(() -> webView.evaluateJavascript(js, null));
+        }
+    }
+
+    /**
+     * Called from Go when an event needs to be emitted to JavaScript
+     * @param eventName The event name
+     * @param eventData The event data (JSON)
+     */
+    public void emitEvent(String eventName, String eventData) {
+        String js = String.format("window.wails && window.wails._emit('%s', %s);",
+                escapeJsString(eventName), eventData);
+        executeJavaScript(js);
+    }
+
+    private String escapeJsString(String str) {
+        return str.replace("\\", "\\\\")
+                .replace("'", "\\'")
+                .replace("\n", "\\n")
+                .replace("\r", "\\r");
+    }
+
+    // Callback interfaces
+    public interface AssetCallback {
+        void onAssetReady(byte[] data, String mimeType);
+        void onAssetError(String error);
+    }
+
+    public interface MessageCallback {
+        void onResponse(String response);
+        void onError(String error);
+    }
+}

build/android/app/src/main/java/com/wails/app/WailsJSBridge.java

@@ -0,0 +1,142 @@
+package com.wails.app;
+
+import android.util.Log;
+import android.webkit.JavascriptInterface;
+import android.webkit.WebView;
+import com.wails.app.BuildConfig;
+
+/**
+ * WailsJSBridge provides the JavaScript interface that allows the web frontend
+ * to communicate with the Go backend. This is exposed to JavaScript as the
+ * `window.wails` object.
+ *
+ * Similar to iOS's WKScriptMessageHandler but using Android's addJavascriptInterface.
+ */
+public class WailsJSBridge {
+    private static final String TAG = "WailsJSBridge";
+
+    private final WailsBridge bridge;
+    private final WebView webView;
+
+    public WailsJSBridge(WailsBridge bridge, WebView webView) {
+        this.bridge = bridge;
+        this.webView = webView;
+    }
+
+    /**
+     * Send a message to Go and return the response synchronously.
+     * Called from JavaScript: wails.invoke(message)
+     *
+     * @param message The message to send (JSON string)
+     * @return The response from Go (JSON string)
+     */
+    @JavascriptInterface
+    public String invoke(String message) {
+        Log.d(TAG, "Invoke called: " + message);
+        return bridge.handleMessage(message);
+    }
+
+    /**
+     * Send a message to Go asynchronously.
+     * The response will be sent back via a callback.
+     * Called from JavaScript: wails.invokeAsync(callbackId, message)
+     *
+     * @param callbackId The callback ID to use for the response
+     * @param message The message to send (JSON string)
+     */
+    @JavascriptInterface
+    public void invokeAsync(final String callbackId, final String message) {
+        Log.d(TAG, "InvokeAsync called: " + message);
+
+        // Handle in background thread to not block JavaScript
+        new Thread(() -> {
+            try {
+                String response = bridge.handleMessage(message);
+                sendCallback(callbackId, response, null);
+            } catch (Exception e) {
+                Log.e(TAG, "Error in async invoke", e);
+                sendCallback(callbackId, null, e.getMessage());
+            }
+        }).start();
+    }
+
+    /**
+     * Log a message from JavaScript to Android's logcat
+     * Called from JavaScript: wails.log(level, message)
+     *
+     * @param level The log level (debug, info, warn, error)
+     * @param message The message to log
+     */
+    @JavascriptInterface
+    public void log(String level, String message) {
+        switch (level.toLowerCase()) {
+            case "debug":
+                Log.d(TAG + "/JS", message);
+                break;
+            case "info":
+                Log.i(TAG + "/JS", message);
+                break;
+            case "warn":
+                Log.w(TAG + "/JS", message);
+                break;
+            case "error":
+                Log.e(TAG + "/JS", message);
+                break;
+            default:
+                Log.v(TAG + "/JS", message);
+                break;
+        }
+    }
+
+    /**
+     * Get the platform name
+     * Called from JavaScript: wails.platform()
+     *
+     * @return "android"
+     */
+    @JavascriptInterface
+    public String platform() {
+        return "android";
+    }
+
+    /**
+     * Check if we're running in debug mode
+     * Called from JavaScript: wails.isDebug()
+     *
+     * @return true if debug build, false otherwise
+     */
+    @JavascriptInterface
+    public boolean isDebug() {
+        return BuildConfig.DEBUG;
+    }
+
+    /**
+     * Send a callback response to JavaScript
+     */
+    private void sendCallback(String callbackId, String result, String error) {
+        final String js;
+        if (error != null) {
+            js = String.format(
+                    "window.wails && window.wails._callback('%s', null, '%s');",
+                    escapeJsString(callbackId),
+                    escapeJsString(error)
+            );
+        } else {
+            js = String.format(
+                    "window.wails && window.wails._callback('%s', %s, null);",
+                    escapeJsString(callbackId),
+                    result != null ? result : "null"
+            );
+        }
+
+        webView.post(() -> webView.evaluateJavascript(js, null));
+    }
+
+    private String escapeJsString(String str) {
+        if (str == null) return "";
+        return str.replace("\\", "\\\\")
+                .replace("'", "\\'")
+                .replace("\n", "\\n")
+                .replace("\r", "\\r");
+    }
+}

build/android/app/src/main/java/com/wails/app/WailsPathHandler.java

@@ -0,0 +1,118 @@
+package com.wails.app;
+
+import android.net.Uri;
+import android.util.Log;
+import android.webkit.WebResourceResponse;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+import androidx.webkit.WebViewAssetLoader;
+
+import java.io.ByteArrayInputStream;
+import java.io.InputStream;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * WailsPathHandler implements WebViewAssetLoader.PathHandler to serve assets
+ * from the Go asset server. This allows the WebView to load assets without
+ * using a network server, similar to iOS's WKURLSchemeHandler.
+ */
+public class WailsPathHandler implements WebViewAssetLoader.PathHandler {
+    private static final String TAG = "WailsPathHandler";
+
+    private final WailsBridge bridge;
+
+    public WailsPathHandler(WailsBridge bridge) {
+        this.bridge = bridge;
+    }
+
+    @Nullable
+    @Override
+    public WebResourceResponse handle(@NonNull String path) {
+        Log.d(TAG, "Handling path: " + path);
+
+        // Normalize path
+        if (path.isEmpty() || path.equals("/")) {
+            path = "/index.html";
+        }
+
+        // Get asset from Go
+        byte[] data = bridge.serveAsset(path, "GET", "{}");
+
+        if (data == null || data.length == 0) {
+            Log.w(TAG, "Asset not found: " + path);
+            return null; // Return null to let WebView handle 404
+        }
+
+        // Determine MIME type
+        String mimeType = bridge.getAssetMimeType(path);
+        Log.d(TAG, "Serving " + path + " with type " + mimeType + " (" + data.length + " bytes)");
+
+        // Create response
+        InputStream inputStream = new ByteArrayInputStream(data);
+        Map<String, String> headers = new HashMap<>();
+        headers.put("Access-Control-Allow-Origin", "*");
+        headers.put("Cache-Control", "no-cache");
+
+        return new WebResourceResponse(
+                mimeType,
+                "UTF-8",
+                200,
+                "OK",
+                headers,
+                inputStream
+        );
+    }
+
+    /**
+     * Determine MIME type from file extension
+     */
+    private String getMimeType(String path) {
+        String lowerPath = path.toLowerCase();
+
+        if (lowerPath.endsWith(".html") || lowerPath.endsWith(".htm")) {
+            return "text/html";
+        } else if (lowerPath.endsWith(".js") || lowerPath.endsWith(".mjs")) {
+            return "application/javascript";
+        } else if (lowerPath.endsWith(".css")) {
+            return "text/css";
+        } else if (lowerPath.endsWith(".json")) {
+            return "application/json";
+        } else if (lowerPath.endsWith(".png")) {
+            return "image/png";
+        } else if (lowerPath.endsWith(".jpg") || lowerPath.endsWith(".jpeg")) {
+            return "image/jpeg";
+        } else if (lowerPath.endsWith(".gif")) {
+            return "image/gif";
+        } else if (lowerPath.endsWith(".svg")) {
+            return "image/svg+xml";
+        } else if (lowerPath.endsWith(".ico")) {
+            return "image/x-icon";
+        } else if (lowerPath.endsWith(".woff")) {
+            return "font/woff";
+        } else if (lowerPath.endsWith(".woff2")) {
+            return "font/woff2";
+        } else if (lowerPath.endsWith(".ttf")) {
+            return "font/ttf";
+        } else if (lowerPath.endsWith(".eot")) {
+            return "application/vnd.ms-fontobject";
+        } else if (lowerPath.endsWith(".xml")) {
+            return "application/xml";
+        } else if (lowerPath.endsWith(".txt")) {
+            return "text/plain";
+        } else if (lowerPath.endsWith(".wasm")) {
+            return "application/wasm";
+        } else if (lowerPath.endsWith(".mp3")) {
+            return "audio/mpeg";
+        } else if (lowerPath.endsWith(".mp4")) {
+            return "video/mp4";
+        } else if (lowerPath.endsWith(".webm")) {
+            return "video/webm";
+        } else if (lowerPath.endsWith(".webp")) {
+            return "image/webp";
+        }
+
+        return "application/octet-stream";
+    }
+}

build/android/app/src/main/res/layout/activity_main.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/main_container"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <WebView
+        android:id="@+id/webview"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent" />
+
+</FrameLayout>

build/android/app/src/main/res/values/colors.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <color name="wails_blue">#3574D4</color>
+    <color name="wails_blue_dark">#2C5FB8</color>
+    <color name="wails_background">#1B2636</color>
+    <color name="white">#FFFFFFFF</color>
+    <color name="black">#FF000000</color>
+</resources>

build/android/app/src/main/res/values/strings.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <string name="app_name">Wails App</string>
+</resources>

build/android/app/src/main/res/values/themes.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <style name="Theme.WailsApp" parent="Theme.MaterialComponents.DayNight.NoActionBar">
+        <!-- Primary brand color. -->
+        <item name="colorPrimary">@color/wails_blue</item>
+        <item name="colorPrimaryVariant">@color/wails_blue_dark</item>
+        <item name="colorOnPrimary">@android:color/white</item>
+        <!-- Status bar color. -->
+        <item name="android:statusBarColor">@color/wails_background</item>
+        <item name="android:navigationBarColor">@color/wails_background</item>
+        <!-- Window background -->
+        <item name="android:windowBackground">@color/wails_background</item>
+    </style>
+</resources>