fix multi Activity support

jobjects have to be compared with env->IsSameObject()
and each Activity needs its own Window instance.
The GtkWindow is still shared between all Activities

src/api-impl-jni/app/android_app_Activity.c

@@ -86,10 +86,19 @@ void activity_start(JNIEnv *env, jobject activity_object) {
 }
 
 JNIEXPORT void JNICALL Java_android_app_Activity_nativeFinish(JNIEnv *env, jobject this, jlong window) {
-	activity_backlog = g_list_remove(activity_backlog, this);
+	GList *l;
+	jobject removed_activity = NULL;
+	for (l = activity_backlog; l != NULL; l = l->next) {
+		if ((*env)->IsSameObject(env, this, l->data)) {
+			removed_activity = l->data;
+			activity_backlog = g_list_delete_link(activity_backlog, l);
+			break;
+		}
+	}
 	activity_update_current(env);
 	activity_close(env, this);
-	_UNREF(this);
+	if (removed_activity)
+		_UNREF(removed_activity);
 	if (activity_backlog == NULL)
 		gtk_window_close(GTK_WINDOW(_PTR(window)));
 }

src/api-impl/android/app/Activity.java

@@ -110,6 +110,8 @@ public class Activity extends Context {
 
 	protected void onStart() {
 		System.out.println("- onStart - yay!");
+		if (window.contentView != null)
+			window.setContentView(window.contentView);
 
 		return;
 	}
@@ -232,7 +234,7 @@ public class Activity extends Context {
 				Constructor<? extends Activity> constructor = cls.getConstructor();
 				Activity activity = constructor.newInstance();
 				activity.intent = intent;
-				activity.window = getWindow();
+				activity.getWindow().native_window = getWindow().native_window;
 				nativeStartActivity(activity);
 			} catch (ClassNotFoundException | NoSuchMethodException | SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
 				onActivityResult(requestCode, 0 /*RESULT_CANCELED*/, new Intent()); // RESULT_CANCELED is the only pre-defined return value, so hopefully it works out for us
@@ -250,7 +252,7 @@ public class Activity extends Context {
 			Constructor<? extends Activity> constructor = cls.getConstructor();
 			Activity activity = constructor.newInstance();
 			activity.intent = intent;
-			activity.window = getWindow();
+			activity.getWindow().native_window = getWindow().native_window;
 			nativeStartActivity(activity);
 		} catch (ClassNotFoundException | NoSuchMethodException | SecurityException | InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException e) {
 			e.printStackTrace();

src/api-impl/android/view/Window.java

@@ -20,6 +20,7 @@ public class Window {
 
 	// FIXME private
 	public long native_window;
+	public View contentView;
 
 	private Window.Callback callback;
 
@@ -39,6 +40,7 @@ public class Window {
 	}
 
 	public void setContentView(View view) {
+		contentView = view;
 		set_widget_as_root(native_window, view.widget);
 	}