Develop Reference

Can I fetch the data being given to an app by its host and store it locally?

I would like to preface my query by saying that I am an absolute beginner when it comes to programming but I really want to realise this project so every little help is deeply appreciated.
I am trying to build an app that needs accurate train data for it to work and from my current research as there is not central government API for railway data , the only accurate data source for train location that I can find is in an other app that uses crowd sourcing to pinpoint the location.
I wanted to know if it is possible to fetch that train data from that app and then use it on my own as it would make my app a lot more reliable and accurate.
The issue currently is that the app only shows graphical representation of the data thats being fed to it from its servers , so I wanted to know if there is a way to access the actual data being sent to the app.
Thank you.

Let me clarify, this is a very broad question and hence will have a very broad answer too.
As far as I can understand from your question is that you want to show TRUE location on a map.
For this, you will have to understand the complete Tracking scenario. Let me explain it to you step-wise below:
There is an app, installed on a device (user) which fetches the GPS location (REAL) data and keeps sending it to a server (backend).
This GPS data is the Lattitude-Longitude coordinates of the device (user).
The server stores this information in their database for queries.
There is another user, different than the one currently sending the location data, who wants to know the location of the first user. The app which he is using will request the server (backend) to send the location data for the device. Which, in turn, will send the latest location data (LatLng coordinates) to the current app. This app will then show the location data over a map.
Now, usually, this process is followed to show one-to-one location data. However, in scenarios like Train Location etc, servers usually collect pool of location data, being received from several users, to cross-verify the actual location (average out, mean, location optimization algorithms etc.) and then display that information over a map.
As per your requirement, which I can understand, you want to get this REAL data directly from either another app or from the server. If you want to get the location data from the server, you will need an API, which serves as a Request-Response platform. However, if you are looking to get the data from another app, it would rather be simpler to get the location data directly, as your APP will also be installed on the device itself.
I would suggest you to kindly read about getting and processing location data, communication with servers over API etc for better understanding and implementation of your requirements.

Making a Android chat app and finding people nearby

Hi everyone I'm in trouble one of my friends asked for a chating Android app which it could find "People Nearby" using this app and first I said yes I can make it but now I'm unable to do.
so It's my very first app that I'm making it for someone I wanted to know if "People Nearby" is simple function for an app or it's complicated and hard to make it
I've seen this kind of apps like swarm that shows you people nearby
but unfortunately I can't find any help or source or tutorial for it the only thing I could find was Google's Nearby Messages which I'm not sure that's what I'm looking for
so I would be very happy if you could help me or at least tell me where I can find a help.

Server side:
(You can use python flask for this kind of simple requirement If you do not have experience in server side scripting)
Your API's must have.
/register -> Registering user profile (unique id, name, location etc) and save it in database.
/receive_location -> Receive location (lat lang values), update in the user profile and check with all records in your database who is in the radius(defined by you or get this as from user) and return the list of user details to client.
Client side:
Have an IntentService which will post location of the client to the server at certain intervals returns the list of users who are in the radius you define.
User googleApiClient to get the location and server .
http://developer.android.com/training/location/retrieve-current.html
Use recycler view to show this result. Send a local broadcast from intent service to tell the activity containing recycler view to update it.

Basic requirement for this is you must have server where all user data is stored.
You must have all users updated latitude and longitude.
To get updated latitude and longitude you must call your api at periodic times.
If you want nearby people search you must call api with your current latitude and longitude, then from server and your api must filter all users location and gives you nearby people.

How can i insert location into mysql database in android

Hi im developing android app based on location. anyone know is it possible to record live location and insert into MySQL database, so whenever user search it should show the map where he or she went with real time. if anyone knows please give an example

Of course it's possible. You would need to listen for location changes through Android's LocationManager service.
One your app is registered as a listener to the service, you will be given periodical updates about the device's latitude and longitude position. These values are what you should persist in a database.
Obviously, your app would need to ask for a few permissions in order to enable GPS tracking. If you're interested in showing the points aswell, you also need to setup a GoogleMap and request an API key for it to work.
As an addition, Android do not natively support direct writing into a MySql database. Your best bet wpuld be to implement a REST API to act as a middle man between your app and the database (hosted online) and post a write request through said API.
Here's some useful links for you to get started:
Official docs for location strategy
Official docs for LocationManager API
p.s., If my answer sounds too broad to you, it is because the thing you asked demands a broad anwer. Do some research and try to recreate an already existing example. Next time you're posting a question, try to narrow down to the very specific thing you'd want to know.

first you need to get current location location.getlatitude() ,location.getlongitude() then save in variable these variable pass the volley library just simple is that volley network method to save value in mysql database.
if you want to change value in database when user change location you should pass declare the method in locationChanged lisner.

There is no direct way to write into a MySQL database. You need to do a interface e.g. with an REST API.
The simplest way that will fit your need is to write some PHP files that are able to perform writes and reads from the database and POST/GET your data.
I found a pretty good example here:
http://www.androidhive.info/2012/05/how-to-connect-android-with-php-mysql/

How to retrieve the location of another android device?

First of all I would like to mention that this would be done with the consent of all users!
That being said, what I am trying to create is an application where the users would see their location and the location of all the other connected users (latitude and longitude).
I am pretty sure the best way to do that would be to send data to a server and then have each device retrieve that data but I would like to know if there exist other ways of doing this. Or perhaps someone could point me in the right direction on how to create such a system with a server retrieving and sending data to android devices ?

GPS coordinates will do for you. You can get the coordinates and save in server then all the coordinates of a particular device can be retrieved by any connected device.
We have Location and LocationManager in android which shall do the job for you. Read more about these in the Android Developers

How to get the name of the nearest city

I have some app that sends some information to the internet from time to time let say ones at day. And I can easily send some coordinates (using the gps position) but I do not want that. The android phone is always connected to the internet via wifi or mobile network. But not always enabled the gps. So is it possible to get the location with wifi or mobile network ? I google this thing and I end up with finding location by gps, I do not want to do that.
Can you give me some ideas what can I do this. I have seen web sites that when I open them they know where am I, so I guess it is possible to find the nearest name of the city just by making a internet request and reading the response or maybe use some service . . .
Thanks

http://developer.android.com/reference/android/location/package-summary.html
http://developer.android.com/reference/android/location/Address.html#getAddressLine(int)
getLocality looks like it may do what you want?
For websites that know where you are, they either use your source IP and look that up (which isn't very reliable for a lot of things), or they use the javascript geolocation APIs as described here:
http://merged.ca/iphone/html5-geolocation
In fact, here's a stack overflow answer on using google API to get to the city name:
Get city name using geolocation