app/internal/headless: [Android] expose Java initialization method

Android apps may want to run Go code independent of the Gio Android Activity.
Expose a Gio.init Java method public for early loading and initialization of
the Go library.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

app/internal/window/Gio.java

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: Unlicense OR MIT
+
+package org.gioui;
+
+import android.content.Context;
+
+import java.io.UnsupportedEncodingException;
+
+public class Gio {
+	private final static Object initLock = new Object();
+	private static boolean jniLoaded;
+
+	/**
+	 * init loads and initializes the Go native library and runs
+	 * the Go main function.
+	 *
+	 * It is exported for use by Android apps that need to run Go code
+	 * outside the lifecycle of the Gio activity.
+	 */
+	public static synchronized void init(Context appCtx) {
+		synchronized (initLock) {
+			if (jniLoaded) {
+				return;
+			}
+			String dataDir = appCtx.getFilesDir().getAbsolutePath();
+			byte[] dataDirUTF8;
+			try {
+				dataDirUTF8 = dataDir.getBytes("UTF-8");
+			} catch (UnsupportedEncodingException e) {
+				throw new RuntimeException(e);
+			}
+			System.loadLibrary("gio");
+			runGoMain(dataDirUTF8, appCtx);
+			jniLoaded = true;
+		}
+	}
+
+	static private native void runGoMain(byte[] dataDir, Context context);
+}

app/internal/window/GioView.java

@@ -42,24 +42,6 @@ public class GioView extends SurfaceView implements Choreographer.FrameCallback
 	private final Handler handler;
 	private long nhandle;
 
-	private static synchronized void initialize(Context appCtx) {
-		synchronized (initLock) {
-			if (jniLoaded) {
-				return;
-			}
-			String dataDir = appCtx.getFilesDir().getAbsolutePath();
-			byte[] dataDirUTF8;
-			try {
-				dataDirUTF8 = dataDir.getBytes("UTF-8");
-			} catch (UnsupportedEncodingException e) {
-				throw new RuntimeException(e);
-			}
-			System.loadLibrary("gio");
-			runGoMain(dataDirUTF8, appCtx);
-			jniLoaded = true;
-		}
-	}
-
 	public GioView(Context context) {
 		this(context, null);
 	}
@@ -69,7 +51,7 @@ public class GioView extends SurfaceView implements Choreographer.FrameCallback
 
 		handler = new Handler();
 		// Late initialization of the Go runtime to wait for a valid context.
-		initialize(context.getApplicationContext());
+		Gio.init(context.getApplicationContext());
 
 		nhandle = onCreateView(this);
 		imm = (InputMethodManager)context.getSystemService(Context.INPUT_METHOD_SERVICE);
@@ -260,7 +242,6 @@ public class GioView extends SurfaceView implements Choreographer.FrameCallback
 	static private native void onFrameCallback(long handle, long nanos);
 	static private native boolean onBack(long handle);
 	static private native void onFocusChange(long handle, boolean focus);
-	static private native void runGoMain(byte[] dataDir, Context context);
 
 	private static class InputConnection extends BaseInputConnection {
 		private final Editable editable;

app/internal/window/os_android.go

@@ -86,8 +86,8 @@ func jniGetStaticMethodID(env *C.JNIEnv, class C.jclass, method, sig string) C.j
 	return C.gio_jni_GetStaticMethodID(env, class, m, s)
 }
 
-//export Java_org_gioui_GioView_runGoMain
-func Java_org_gioui_GioView_runGoMain(env *C.JNIEnv, class C.jclass, jdataDir C.jbyteArray, context C.jobject) {
+//export Java_org_gioui_Gio_runGoMain
+func Java_org_gioui_Gio_runGoMain(env *C.JNIEnv, class C.jclass, jdataDir C.jbyteArray, context C.jobject) {
 	if res := C.gio_jni_GetJavaVM(env, &theJVM); res != 0 {
 		panic("gio: GetJavaVM failed")
 	}