Develop Reference

Convert Spritekit Game to Android?

Are there any new options for converting a spritekit game to android? It seems the only options are to recode everything in Java or to use Cocos2D, LibGDX, etc.

Unfortunately ... no :{
And the cross-platform SpriteBuilder with the Apportable service that let you convert a Swift Cocos project to Android is no longer available (they got bought out by Google I believe).
SpriteBuilder is still available on GitHub but it's not active afaik and is abandoned.
So... what to do?
I would focus on iOS... you can make your game "cross platform" by converting to macOS and tvOS... This is where all of the money is in the market... Apple products...
If your goal however is cross platform, then you can look at Xamarin.forms alongside CocosSharp which will give you write once run everywhere games in C#
You also have regular Xamarin available to write gameplay code in C#, and share it across Android and SpriteKit wrappers written in C# as well.
Another thing to look at is Silver which has Swift wrappers for Android.. thus letting you port Gameplay code almost directly...
In all scenarios you will have to find another game engine for whatever Android solution you use..
IMO, developing with Swift for Apple is much easier and more fun than anything I've ever done with Android dev, even though I prefer Android devices (go figure), and since the revenue is higher it is sort of a no-brainer for starting up.

There are no easy options for supporting Android with a SpriteKit game, but with a little bit of work and not too much difficulty you can recode your game to use Cocos2d-x. I just completed such a project for my game. It took me about four months working half time. I've posted some tips here: http://doffen.org/porting-spritekit-to-cocos2d-x.

I would suggest to have a look here: http://processing.org/
and here : http://www.ricardmarxer.com/fisica/
Fisica is a wrapper of jBox2D for Processing and is quite easy to use. There are a few tweaks for android but nothing too hard.
I did it in the opposite direction (converting my fisica-based game to SpriteKit) and it was quite easy to create regex replacement to easily migrate to swift syntax.

iOS + Android 2D Game Engine

I already found some answers to this question here but they were all two years old or more.
Can anyone suggest me a cross platform (iOS+Android) mobile 2D game engine (Java or C++)?
I'd go with AndEngine but it supports Android only.
Thank you.

I recommend libGDX. As you may have read from a few of the other threads in StackOverflow, it is one of the popular ones and there is sufficient material provided to assist you to get familiar with.
Here is their Github page, which has loads of information to get you started (see external tutorials in the wiki). I would also like to recommend dermetfan's libGDX channel for a basic introduction that I have found useful with certain components (search dermetfan libGDX in youtube, would provide link but I'm restricted to two links).
Personally, I have used libGDX as a mobile 2D game engine for a work project, and I've found it really nice. Hope this helps!

Which AR (Augmented Reality) framework (Android & iOS) is suitable for my situation

My Situation
I want to build an Application that can recognize an Image to produce a corresponding model.
i.e. I focus the camera to show a printed image on the card that is designed by myself ( apple logo ) , then it will show a 3D model(.md2) on the screen which is also designed by myself.
I have googled many framework that worked on both Android & iOS, but the documentations are very limited and the trial version does not support me to test it.
for example,
http://www.metaio.com/sdk/
But their demo is not comprehensive enough to suite my situation
My Question
1.Would anyone can share their experience of developing with AR framework (not the AR core) on Android & iOS?
2.Is there any framework that support me to add a image as a key then it will map to my model with just a couples line of codes?
3.if Q2 is not possible, is there any approaches of some framework can also archive the some goal but more complex ?
//Logic flow
String key = "APPLE";
sdk.putKeyImage(key,apple.png);
...
if (sdk.identifiedAs(key)){
//Do something
//Example
sdk.showApple3DModel();
play(showSnakeEatApple.mp4);
}

I'm an android app developer. So according to my experince for android, you can go for
Vuforia (https://developer.vuforia.com/resources/sdk/android)
Wikitude (http://www.wikitude.com/developer/documentation/android)
These above 2 are enough good to implement AR app in android.
Vuforia is having well documented, also they have more libraries & mainly those are free. & Wikitude is best for making apps faster. I recommend you to use any of these for your AR app development in android.

I guess you should compare several AR frameworks to find a proper solution for your problem. Many different AR tools come to my mind. For example, Vuforia, LayAR, Kudan AR. To take a deeper look at the variety of possible options read the comprehensive comparison of the most popular frameworks: http://cases.azoft.com/top-5-tools-creating-augmented-reality-apps/

yes i did work on it not much but little bit i did research on augmented reality and after research i found one open source and cross platform well known sdk its name is
VUFORIA SDK
there are various SDK you find on google but trust me VUFORIA is best and flexible who gives lots of option
for that you need to install NDK in eclipse cause it have core cpp code who compile by NDK in eclipse
video tutorial click here
sdk and documentation click here
steps click here
hope it will be helpful for you thank you happy coding

andengine vs no framework development

I am trying to learn to create 2D games on android, and I have heard that andengine is one of the best tools for that. I tried using it, but unfortunately there I have encountered numerous issues with andengine having little documentation, and no stable place where I can learn things. So my question is that what would you recommend to a completely newbie developer? Should I try learning andengine, or learn things the hard way? And can you please provide some good links to learn? So far a lot of links I found were quite old and would not work properly all the time.
Thanks to anyone for their help.
Also just to clarify, I am middle skilled in 2D game development (especially in java and C++), so I know the basic structure, my main issue is making things run on an android since I am completely new to android itself.

With andengine, your best bet is to download, compile and run the sample games and examples. From reading through and understanding the source code for those, you'll learn how to use it. The examples in particular are effectively documentation, they're very good!

Open GL 3D library for iOS (and Android)?

Is there some free and easy to use 3D library for iOS (and Android) that simplifies Open GL ES framework. Just like there is cool WebGL library: ThreeJS for javascript.
So far I saw Unity but it's not free and I would like something simplified.
My usage would be setting the scene, meshes, camera, rotating the camera etc...

For Android you can use AndEngine which supports GL ES1 and GL ES2. For IOS you can use Cocos2D.

I decided to go with Cocos3D because it has all the features I need and is similar to JS libraries. It is free and you don't have to use any special engines with it.

Well, there is Sparrow for iOS, and as for Android you can consider AndEngine
(easier) or LibGDX (faster).

One option I believe is SiO2.. And Oolong too.. I once played with blender and SiO2 and it went well..If you are only interested in 2D games only then Cocos2D is best bet for iphone..
For android AndEngine is good,and I believe SiO2 works for android too..

Ahh, Unity did give away the iOS/Android versions back in March/April this year - maybe if you asked them nicely?
OpenSceneGraph has a large and active following in the Vis/Sim community, and is starting to creep into games, here's a couple iOS/game related topics from their forums:
http://forum.openscenegraph.org/viewtopic.php?t=10291
http://forum.openscenegraph.org/viewtopic.php?t=10308 (p.2 of this thread has links to a couple osg-based games in the iTunes store)

For Leaning very basic of open GL for iOs I would suggest to have a look at this http://antonholmquist.com/blog/opengl-es-2-0-ios-tutorial-getting-started/. This gives the basic idea of vertex and fragment shaders. After going through this a beginner can go through other tutorials which explains the detailed concepts of openGL.
I have gone through so many links but this one explains the basic really well.