add support for 'android:hasCode="false"' and update "examples/minimal" to use it (#33)

Allow projects to have an AndroidManifest.xml file that has `android:hasCode="false"` as per Android documentation here:
https://developer.android.com/ndk/samples/sample_na

**Changes**
- removes validation rules around requiring Java files
- simplifies the minimal example to no longer require Java
- fixes `src/android/android.zig` to compile on latest Zig nightly

Fixes #32

Author: silbinarywolf

examples/minimal/android/AndroidManifest.xml

@@ -7,6 +7,7 @@
         android:icon="@mipmap/ic_launcher"
         android:label="@string/app_name"
         android:theme="@android:style/Theme.NoTitleBar.Fullscreen"
+        android:hasCode="false"
         tools:targetApi="31">
         <activity
             android:name="android.app.NativeActivity"

examples/minimal/android/src/NativeInvocationHandler.java

@@ -32,7 +32,13 @@ pub fn build(b: *std.Build) void {
         apk.addResourceDirectory(b.path("android/res"));
 
         // Add Java files
-        apk.addJavaSourceFile(.{ .file = b.path("android/src/NativeInvocationHandler.java") });
+        // - If you have 'android:hasCode="false"' in your AndroidManifest.xml then no Java files are required
+        //   see: https://developer.android.com/ndk/samples/sample_na
+        //
+        //   WARNING: If you do not provide Java files AND android:hasCode="false" isn't explicitly set, then you may get the following error on "adb install"
+        //      Scanning Failed.: Package /data/app/base.apk code is missing]
+        //
+        // apk.addJavaSourceFile(.{ .file = b.path("android/src/X.java") });
         break :blk apk;
     };
 

examples/minimal/build.zig

@@ -72,8 +72,16 @@ fn nativeActivityOnCreate(activity: *androidbind.ANativeActivity, savedState: []
     log.debug("Successfully started the app.", .{});
 }
 
+comptime {
+    if (builtin.abi.isAndroid()) {
+        @export(&NativeActivity_onCreate, .{ .name = "ANativeActivity_onCreate" });
+    } else {
+        @compileError("This example cannot run on targets other Android");
+    }
+}
+
 /// Android entry point
-export fn ANativeActivity_onCreate(activity: *androidbind.ANativeActivity, rawSavedState: ?[*]u8, rawSavedStateSize: usize) callconv(.C) void {
+fn NativeActivity_onCreate(activity: *androidbind.ANativeActivity, rawSavedState: ?[*]u8, rawSavedStateSize: usize) callconv(.C) void {
     const savedState: []const u8 = if (rawSavedState) |s|
         s[0..rawSavedStateSize]
     else

examples/minimal/src/minimal.zig

@@ -13,6 +13,9 @@ const android_builtin = struct {
     pub const package_name: [:0]const u8 = ab.package_name;
 };
 
+/// Writes the constant string text to the log, with priority prio and tag tag.
+/// Returns: 1 if the message was written to the log, or -EPERM if it was not; see __android_log_is_loggable().
+/// Source: https://developer.android.com/ndk/reference/group/logging
 extern "log" fn __android_log_write(prio: c_int, tag: [*c]const u8, text: [*c]const u8) c_int;
 
 /// Alternate panic implementation that calls __android_log_write so that you can see the logging via "adb logcat"
@@ -92,7 +95,7 @@ const LogWriter = struct {
     /// logs with the package name.
     ///
     /// To workaround this, we bake the package name into the Zig binaries.
-    var tag: [:0]const u8 = android_builtin.package_name;
+    const tag: [:0]const u8 = android_builtin.package_name;
 
     level: Level,
 
@@ -166,6 +169,8 @@ const Panic = struct {
     threadlocal var panic_stage: usize = 0;
 
     fn panic(message: []const u8, ret_addr: ?usize) noreturn {
+        @branchHint(.cold);
+        if (comptime !builtin.abi.isAndroid()) @compileError("do not use Android panic for non-Android builds");
         const first_trace_addr = ret_addr orelse @returnAddress();
         panicImpl(first_trace_addr, message);
     }
@@ -199,7 +204,12 @@ const Panic = struct {
         // }
         var act = posix.Sigaction{
             .handler = .{ .handler = posix.SIG.DFL },
-            .mask = posix.empty_sigset,
+            .mask = if (builtin.zig_version.major == 0 and builtin.zig_version.minor == 14)
+                // Legacy 0.14.0
+                posix.empty_sigset
+            else
+                // 0.15.0-dev+
+                posix.sigemptyset(),
             .flags = 0,
         };
         // To avoid a double-panic, do nothing if an error happens here.
@@ -236,14 +246,7 @@ const Panic = struct {
     /// - Provide custom "io" namespace so we can easily customize getStdErr() to be our own writer
     /// - Provide other functions from std.debug.*
     fn panicImpl(first_trace_addr: ?usize, msg: []const u8) noreturn {
-        // NOTE(jae): 2024-09-22
-        // Cannot mark this as cold(true) OR setCold() depending on Zig version as we get an invalid builtin function
-        // comptime {
-        //     if (builtin.zig_version.minor == 13)
-        //         @setCold(true)
-        //     else
-        //         @cold(true);
-        // }
+        @branchHint(.cold);
 
         if (enable_segfault_handler) {
             // If a segfault happens while panicking, we want it to actually segfault, not trigger

src/android/android.zig

@@ -203,13 +203,18 @@ fn doInstallApk(apk: *Apk) std.mem.Allocator.Error!*Step.InstallFile {
                 }
             }
         }
-        if (apk.java_files.items.len == 0) {
-            // NOTE(jae): 2024-09-19
-            // We can probably avoid this with a stub or something but for now error so that an "adb install"
-            // doesn't give users:
-            // - Scanning Failed.: Package /data/app/base.apk code is missing]
-            try errors.append(b.fmt("must add at least one Java file to build", .{}));
-        }
+        // NOTE(jae): 2025-05-06
+        // This validation rule has been removed because if you have `android:hasCode="false"` in your AndroidManifest.xml file
+        // then you can have no Java files.
+        //
+        // If you do not provide Java files AND android:hasCode="false" isn't set, then you may get the following error on "adb install"
+        // - Scanning Failed.: Package /data/app/base.apk code is missing]
+        //
+        // Ideally we may want to do something where we can utilize "aapt2 dump X" to determine if "hasCode" is set and if it isn't, throw
+        // an error at compilation time. Similar to how we use it to extract the package name from AndroidManifest.xml below (ie. "aapt2 dump packagename")
+        // if (apk.java_files.items.len == 0) {
+        //     try errors.append(b.fmt("must add at least one Java file to build OR you must setup your AndroidManifest.xml to have 'android:hasCode=false'", .{}));
+        // }
         if (errors.items.len > 0) {
             printErrorsAndExit("misconfigured Android APK", errors.items);
         }