Box2D | simulating rigid bodies | Build Tool library

From my understanding, in Box2d, objects will collide with another object if the other object's category is in the mask.

I have set up a really simple scene where I have a square that should fall through the floor. For testing purposes I have made it so the mask and the category are completely different on the square and floor like below

I'm trying to program a simulation for my physics paper. I saw Box2d as an option. My question is, are physics game engines like Box2d accurate for this kind of purposes?

I am trying to make a portable framework library that works between Linux and Windows, however whenever I compile my code on Linux I keep running into an error:

For a Box2D composition, I need this code to avoid unintentional clicks:

I work with this, and realized that links always get fired if you drag them. I would like to avoid that, and coded this:

I'm facing a problem with an http request done in HTTP.java.

On desktop all works fine (that request is not performed because it's necessary only on Android).

In Android all works without that http request.

After that that http request is made, all others fail after timeout with UnknownHostException error, as if they no longer have access to the internet connection, even if it is active. Also after minutes and after the onResume all http requests fail. Although the app cannot get an http response, the AdMob ad appears in my App, so I think that probably the connection works (or does the AdMob library cache some ads and show them when needed?).

Often, in these cases sometimes it works again:

• uninstalling and reinstalling the App from Android Studio
• closing the App, waiting some minutes and reopening it
• clearing App data from the device
• waiting an undefined amount of time

❗ After several attempts I discovered that as soon as the problem occurs, almost every time, if I activate the airplane mode and then disable it, the data connection is deactivated and then reactivated, and the App can immediately execute all subsequent http requests without having to do anything else on your device and without even having to reopen the application.

• tested with wifi on a 1GB fibra network: same error
• I checked the connection: it is stable, in wifi and also with SIM
• in the manifest there is the permission for using internet (otherwise it would never have worked)
• at the same time, the same App on desktop works perfectly and at the best speed, receiving http responses in less than 1 second, so the server isn't the problem
• I tested also with the url https://www.google.it: same error, the same url is reachable in the device via browser in less than 1 second
• as in the line .timeout(10000) I'm using a timeout of 10 seconds, the server has timeout set to 60 seconds
• checked the server SSL "quality" at https://www.ssllabs.com/ssltest: got "A" in "Overall Rating"
• done the SIM "reboot" directly with a Vodafone operator

I'm testing on a real device with a flat 4G connection and with wifi, with "NetGuard - no-root firewall" VPN App installed.

This VPN works very well with all the other apps and probably mine too, but I can't rule out that it's the problem, although I hardly think it is (I use it since years without problems).

There is something wrong in my code? Or at least, how can I know the exact cause of this error?

Thanks.

AndroidLauncher.java:

I am making a game in Kotlin.Using Libgdx and Box2d

1.function creates bodies via Box2d and adds these bodies in bodyArrayList:ArrayList

2.function creates textures and adds these textures in textureArrayList

3.function is matching items of bodyArrayList with items of textureArrayList. The function has for loop.

4.function is removing bodies when crash a wall.

5.function is removing textures when crash a wall.

All functions are working in update() method. All these are working perfectly. However because I cannot remove items of te ArrayLists while for loop works on these ArrayLists, items of ArrayList is increasing and the game is starting slowing downn 1 hour later. The ArrayLists' size is going up as you guess. If I try to remove items of ArrayLists I am taking exceptions in matching() function as you guess.

My question is how can I remove these items from ArrayLists while "for loop" is working in a safe manner.

1.function creates bodies

I am trying to render the bodies that I made in the open-source tool using ShapeRenderer. It seems to work for simple shapes like a square by simply retrieving the vertices and giving them back to the ShapeRenderer. However, when it comes to complex Bodies with about 9 polygons (the one I'm trying to render) I've tried rendering the polygons one by one, but it looks like it's giving me the same polygon over and over again, no matter how I initialize or go through my list of Vector2[]. I've been stuck on this for a while now, and any insight would help. (I'm using the BodyEditorLoader class to get the vertices)

BodyEditorLoader Class where I get my vertices from. (Gotten from open source library)

This is quite bizarre in my opinion. I create fixtures based on a fixtureDef. I use the libGDX version of Box2D. This is my code: