Improve Android build prereq checks and add build.sh

android/build.sh

@@ -0,0 +1,74 @@
+#!/bin/bash
+# Build the Handoff Android app — checks prereqs and builds everything.
+set -euo pipefail
+
+cd "$(dirname "$0")"
+
+echo "==> Handoff Android Build"
+echo "  ────────────────────────"
+echo ""
+
+# ─── Detect Android SDK ──────────────────────────────────────────
+if [ -z "${ANDROID_HOME:-}" ]; then
+    for dir in "$HOME/Library/Android/sdk" "$HOME/Android/Sdk" /opt/android-sdk; do
+        if [ -d "$dir" ]; then
+            export ANDROID_HOME="$dir"
+            break
+        fi
+    done
+fi
+if [ -z "${ANDROID_HOME:-}" ]; then
+    echo "ERROR: Android SDK not found."
+    echo "  Install Android Studio: brew install --cask android-studio"
+    echo "  Then open it once to complete the SDK setup wizard."
+    exit 1
+fi
+
+# ─── Generate local.properties if missing ─────────────────────────
+if [ ! -f local.properties ]; then
+    echo "  Generating local.properties..."
+    echo "sdk.dir=$ANDROID_HOME" > local.properties
+fi
+
+# ─── Select JDK 17 if available ───────────────────────────────────
+if command -v /usr/libexec/java_home &>/dev/null; then
+    if /usr/libexec/java_home -v 17 &>/dev/null; then
+        export JAVA_HOME=$(/usr/libexec/java_home -v 17)
+    fi
+fi
+
+# ─── Build Go bridge if needed ────────────────────────────────────
+if [ ! -f app/libs/gobridge.aar ]; then
+    echo "  gobridge.aar not found — building Go bridge..."
+    (cd gobridge && ./build-aar.sh)
+    echo ""
+fi
+
+# ─── Build APK ────────────────────────────────────────────────────
+echo "==> Building debug APK..."
+./gradlew assembleDebug
+
+APK="app/build/outputs/apk/debug/app-debug.apk"
+echo ""
+echo "==> Build complete: $APK"
+ls -lh "$APK"
+
+# ─── Install if device connected ─────────────────────────────────
+ADB="$ANDROID_HOME/platform-tools/adb"
+if [ -x "$ADB" ]; then
+    DEVICES=$("$ADB" devices 2>/dev/null | grep -w device | head -1 || true)
+    if [ -n "$DEVICES" ]; then
+        echo ""
+        echo "==> Installing on connected device..."
+        "$ADB" install -r "$APK"
+    else
+        echo ""
+        echo "  No device connected. To install later:"
+        echo "    $ADB install $APK"
+    fi
+else
+    echo ""
+    echo "  adb not found. To install on a device:"
+    echo "    sdkmanager --install 'platform-tools'"
+    echo "    \$ANDROID_HOME/platform-tools/adb install $APK"
+fi

android/gobridge/build-aar.sh

@@ -5,11 +5,33 @@ cd "$(dirname "$0")"
 
 echo "==> Checking prerequisites..."
 
+# 1. Go
 if ! command -v go &>/dev/null; then
-    echo "ERROR: Go is not installed. Install from https://go.dev/dl/"
+    echo "ERROR: Go is not installed. Install from https://go.dev/dl/ or: brew install go"
     exit 1
 fi
 
+# 2. Java — required for gomobile bind (jar/javac)
+if ! command -v java &>/dev/null; then
+    echo "ERROR: Java is not installed."
+    echo "  Install JDK 17: brew install --cask temurin@17"
+    exit 1
+fi
+
+JAVA_VER=$(java -version 2>&1 | head -1 | sed 's/.*"\([0-9]*\).*/\1/')
+if [[ "$JAVA_VER" -gt 21 ]]; then
+    # Try to find JDK 17 automatically
+    if /usr/libexec/java_home -v 17 &>/dev/null; then
+        export JAVA_HOME=$(/usr/libexec/java_home -v 17)
+        echo "  JAVA_HOME=$JAVA_HOME (auto-selected JDK 17; JDK $JAVA_VER is too new)"
+    else
+        echo "ERROR: JDK $JAVA_VER is too new for Android tooling (max 21)."
+        echo "  Install JDK 17: brew install --cask temurin@17"
+        exit 1
+    fi
+fi
+
+# 3. Android SDK
 if [ -z "${ANDROID_HOME:-}" ]; then
     # Try common locations
     for dir in "$HOME/Library/Android/sdk" "$HOME/Android/Sdk" /opt/android-sdk; do
@@ -19,13 +41,15 @@ if [ -z "${ANDROID_HOME:-}" ]; then
         fi
     done
     if [ -z "${ANDROID_HOME:-}" ]; then
-        echo "ERROR: ANDROID_HOME not set and Android SDK not found"
+        echo "ERROR: ANDROID_HOME not set and Android SDK not found."
+        echo "  Install Android Studio: brew install --cask android-studio"
+        echo "  Then open it once to complete the SDK setup wizard."
         exit 1
     fi
 fi
 echo "  ANDROID_HOME=$ANDROID_HOME"
 
-# Find NDK
+# 4. Android NDK
 if [ -z "${ANDROID_NDK_HOME:-}" ]; then
     NDK_DIR="$ANDROID_HOME/ndk"
     if [ -d "$NDK_DIR" ]; then
@@ -35,15 +59,36 @@ if [ -z "${ANDROID_NDK_HOME:-}" ]; then
     fi
 fi
 if [ -z "${ANDROID_NDK_HOME:-}" ]; then
-    echo "ERROR: Android NDK not found. Install via: sdkmanager --install 'ndk;27.0.12077973'"
+    echo "ERROR: Android NDK not found."
+    echo "  Install via: sdkmanager --sdk_root=\"\$ANDROID_HOME\" --install 'ndk;27.0.12077973'"
     exit 1
 fi
 echo "  ANDROID_NDK_HOME=$ANDROID_NDK_HOME"
 
+# 5. Android SDK platform (API 26 required by gomobile)
+if [ ! -d "$ANDROID_HOME/platforms/android-26" ]; then
+    echo "  Android SDK platform 26 not found — installing..."
+    if command -v sdkmanager &>/dev/null; then
+        sdkmanager --sdk_root="$ANDROID_HOME" --install 'platforms;android-26' || {
+            echo "ERROR: Failed to install SDK platform 26."
+            echo "  Install manually: sdkmanager --sdk_root=\"\$ANDROID_HOME\" --install 'platforms;android-26'"
+            exit 1
+        }
+    else
+        echo "ERROR: Android SDK platform 26 not found and sdkmanager not available."
+        echo "  Install command-line tools: brew install --cask android-commandlinetools"
+        echo "  Then: sdkmanager --sdk_root=\"\$ANDROID_HOME\" --install 'platforms;android-26'"
+        exit 1
+    fi
+fi
+
 echo "==> Installing gomobile..."
 go install golang.org/x/mobile/cmd/gomobile@latest
 go install golang.org/x/mobile/cmd/gobind@latest
 
+# Ensure GOPATH/bin is in PATH
+export PATH="$(go env GOPATH)/bin:$PATH"
+
 echo "==> Initializing gomobile..."
 gomobile init