Develop Reference

What are the criteria to select the appropriate resolution to build a 2D game?

I'd like to know, how can I select the best resolution to build a 2D game in android?

You can go with 1920*1080 - this will give you a clear output on most current devices - and use FitViewPort or ExtendViewPort as you wish.

I'm rendering my graphics in 2K resolution (i.e. in 3040 x 1,40 - aiming most popular high-end phones of today, i.e. Samsung S10) so it will definitely look well on screens with higher resolution. And then I'm using camera zoom to display it properly on current screen resolution. It does take a bit more space for graphics and it's probably loosing some frame per second but on today's devices it's acceptable loss. My games run smooth even on older devices, so I don't think it's an issue at all.

Android 2d game engine that supports multi screen resolution

I'm looking for an android 2d game engine, where you can create your game at the resolution you want, and the game will work the same on every phone, no matter the resolution, maybe by auto creating thoose black rectangles.
I was working with libGDX, but i could not find any ways to do that, just some viewport scalling methods, that will make the game graphics quality crappy.
I also used to work with the android sdk using surfaceview, and i had to code everything by a ratio, and also scale the bitmaps by a ratio, but i don't really think that that is a good way to do it.
Are there any android game engines that support every device resolutions?

You are asking for something you won't get. I doubt that there's a tool or engine released to the public that will automagically fix all resolutions possible to fit your needs. This is something that developers has to tackle, and it's a nice thing to handle independently.
Now when working in LibGdx, did you even try to use Texture filters? Linear filtering will smoothen your images when enlarged. They may get some blur but I've released a commercial game using this method.
All in all, i really think you should give it another shot. LibGdx will spare you a large amount of troubles and in my opinion; The request of yours ain't that hard to overtake.

Building Android Apps using Adobe AIR

I am building an android application with Adobe Flash cs6 and Adobe AIR for the first time. Initially it looked good but later I faced a lot of problems. What I have till now is more of movieclip and less as3 coding. My app scales automatically according to different screen sizes. However since there are more movieclips my app somewhat lags in Kindle Fire. My question:
1. Do I need to convert my movie clips to Bitmaps or something? How is that done?
2. While converting to bitmap, do I need to specify width and height of the movieclips? Doesnt it get scaled automatically acc. to screen size?
Well, I am new to actionscript, AIR and stuff... so any help would be appreciated.

All display objects have 'cacheAsBitmap' and 'cacheAsBitmapMatrix' propertiues that help with performance, but only for certain class of objects (primarily those not frequently changed).
More info: Caching display objects
Also, make sure you have HW acceleration turned on for maximum benefit, especially on mobile: HW acceleration

Android devices GL_MAX_TEXTURE_SIZE limitation, safe texture size

I am working with AndEngine and OpenGL ES 2.0. I keep reading about GL_MAX_TEXTURE_SIZE and how I should keep my texures under 1024x1024. I started wrong before and while using tilesets in TMX extension (doesn't really matter what it is, if you don't know AndEngine) I get to a tileset that makes a texture wider than 1024px. I am thinking of splitting the tileset into two, making them "safe". But I can't find any device released in last couple of years that has this limit set under 2048x2048. Is there any list or website I can use to filter devices by GL_MAX_TEXTURE_SIZE?
I read the following questions:
Minimum required Texture Size for compliance with OpenGL-ES 2.0 on Android?
Is there any Android device with screen size greater than GL_MAX_TEXTURE_SIZE?
And I used this site to search for devices. But I can't search by/filter by GL_MAX_TEXTURE_SIZE, which makes the search tedious. I am asking mostly because I started wrong, it's a hobby project and the amount of work might be too large compared to the number of possible devices that will be enabled (I expect 0).

1024x1024 is about the safest you can go on any device, especially on older ones. Newer devices shouldn't have any problem, although I've seen recent devices (I recall a Galaxy Nexus, the newest ICS update fixed that though) render white quads with texture sizes of size 2048x1024.
If you're targeting new devices and want to keep older ones compatible, it shouldn't hurt to split your tilesets. After all, you aren't likely to do too many context switches if you use two or three spritesheets for background, etc.

If you still have the individual image files, breaking them into small sized Atlases or custom sized atlases is easy if you use the TexturePacker2 tool from the LibGdx library.
I don't know the exact limitation of devices, but it's always better to take into consideration the lowest end of device you want to support and build upward from there. Using the LibGdx tool, you can easily change your mind later, so it's the most flexible solution.
Look at:
LibGdx TexturePacker

OpenGL Android App works on most phones but textures come up white on Xoom

My Android app has been out for several months and works fine on any number of WVGA phones like the Droid, Droid 2, Galaxy, etc.
On the Motorola Xoom, however, a small portion of the textures load with white boxes where the images should be.
Researching online the most usual cause for this appears to be not using power of two textures. This seems an unlikely explanation since they work fine on so many other devices. Also, I am using power of two textures. The one caveat there is that I'm loading a bunch of bitmaps into a 1024 by 1024 texture dynamically. The code I'm using is from a now defunct library called Rokon, the relevant texture atlas code is here: http://code.google.com/p/rokon/source/browse/trunk/src/com/stickycoding/rokon/TextureAtlas.java?r=260 -- Like I said, I'm skeptical this could be the cause since it works on so many other devices AND many of the textures I am loading this way do work fine.
But I'm not sure what else could be causing it. A memory issue seems unlikely given that amount of memory available on the Xoom compared to the other devices the app works on.
Right now I don't own a zoom, but I can replicate the issue via DeviceAnywhere (where I see white backgrounds).
Nothing of interest shows up in LogCat either.
I know this isn't much to go on, but I'm at a loss here, what kinds of potential causes should I be looking at here? Thanks in advance for any ideas.

Try using glGetError() to see if OpenGL throws any errors

Is your application 2D or 3D? When you're drawing your sprites on the screen; which method are you using?
If your texture is white during onDrawFrame that probably depends on:
An untextured quad (using VBO:s or standard Vertex Arrays) - probably not, because it works on other devices
Xoom lacks support of the draw_texture extension - if you're using 2D
Xoom lacks support of VBO:s (Vertex Buffer Objects) - probably not, almost every Android device out there supports VBO:s
Do you have any sort of texture compression implemented that Xoom doesn't support?
At runtime, use this code to get the extensions and check if they're available:
String extensions = gl.glGetString(GL10.GL_EXTENSIONS);
boolean supportsDrawTexture = extensions.contains("GL_OES_draw_texture");
// Continue here and sooner or later you should see where Xoom lacks support
// where other devices doesn't.

Is it possible that you're falling foul of Android's automatically-resize-bitmaps behaviour? Print out the bitmap sizes as they are loaded to check, or move them to res/drawable-nodpi to avoid the behaviour entirely.

Is it possible that your texture exceeds 2048 pixels width or height? That's the maximum allowed texture size on XOOM.