I wanted to make an android application where I can send a photo and everyone who has this app has access to this photo and can evaluate it with a wanted note, my doubt is what I should study to be able to make an app like this .Thank you
ps: I already made an application for android, a matrix calculator.
I'll give you an example of a possible way to do it, so you have an idea of what you need to learn (in addition to the basics of Java and Android):
Photos and their notes need to be stored somewhere. Usually in tables of a database (MySQL or PostgreSQL, to name two of the most popular and free). This involves learning the basics of SQL .
(Instead of directly saving the binary data representing the photo in a BLOB-type field, you can alternatively save those photos to files and save the paths of those files to the database table. p>
The database typically resides on a remote machine that is connected to the Internet and is called server . You could access the tables directly from the cell phone but this is not the correct way to do it; the most correct is the cell call Web Services, which are basically URLs that when being called execute code on the server that accesses the database and return this data in the Web Service response itself. Then there are a few more things to study: Web Services (and also the basics of the HTTP protocol if you want to know how they work underneath the wipes) to write these Web Services, which can be Java itself, in case you do not want to study PHP, Javascript or some other.
(Some additional details: These Web Services run in an environment called an application server , which in the case of Java might be Tomcat . As we live in cloud times, there are several free services that allow you to create a remote (virtual) machine where you can run an application server and I do not have a lot of experience in creating them with tools, I think people often use something called JAX-RS . of the Web Service to communicate with the bank, will be used JDBC .And, to transmit small data organizations through the Web Service, for example the notes of a photo, you should study the data format < strong> JSON ).
On Android, to call Web Services, you will need to study AsyncTasks , so your application does not crash the screen while calling the Web Service, which in turn can be called using a library such as to OkHttp from Square. And if your cell phone takes too big pictures that take up too much memory (RAM, not storage memory) and also reduce the amount of data to transmit, you'll have to learn how to reduce the size of Bitmaps that contain the photos before transmitting them.
