Develop Reference

How to create a system app for custom ROM

We have a custom ROM for a device we are making and what I want to do is make our own custom Settings app to replace the settings app that comes already built in android.
I cant really find any documentation on how to even create a system app. It does not appear you can create it in Android Studio, I tried looking on the AOSP site and didnt find anything there related to creating system apps. The few things I did find were on here where you would put android:sharedUserId="android.uid.system" in your manifest and then has to be signed with the same key as the ROM but after that I cant find anything.
The settings app I want to create would need access to the framework.jar to be able to use the hidden framework API's.
Does anyone have any information or know where I can find this information on how to go about actually creating a system app?

You may want to research how to make a Device Tree Overlay (dto). Basically it is your code, reformatting the base code, into what you want. https://source.android.com/devices/architecture/dto?hl=en

Since you said you use Gradle, you should put first build you apk and put them in you vender folder, and next important thing is to create a mk/bp file to tell the Android build system how to deal with this pre-built apk.
P.S. If you system app highly depends on Android hidden api, make sure you have the right version of framework.jar in you Android Studio project, or, as what I alway did, create apps directly in AOSP, in this case, you can just check the code structure of the original Settings app in AOSP
this tutorial may help you.

Any way to see all the methods that don't work at once? Android Studio

I have to estimate the time it takes to update a specific application made for Android 4.4 to Android 10 and I need to see all the methods that are deprecated or not working. Is there any way to see the methods without going file by file? (I'm using Android Studio with Java)
When I build the application I only get one or two types of error at a time, when I correct them I get another one and so on.
Thanks and best regards.
P.S: How long does it take you to update something like that? I'm a junior and I'm a little lost doing this.

Here, go to Analyze -> Inspect code. After inspecting check maturity there you will have depreciated methods. (Don't forget to change minSdk)
After you will do that it give you method with a warning and you can filter it by having API not support warning

Android - 'Checking/Inspecting' Android Application Code

I've tried a number of searches but can't find anything applicable, it may be because I'm just not asking the right question! So please feel free to redirect me if this has been covered elsewhere.
I'm new to Android and to development, but have an idea to use an Application to check other simple apps on the device for potential security holes (this is to design a prototype as part of a course of study).
Before I go any further, is it feasible to use an application to check through/parse/inspect the source code of another app, searching for instances of text/commands/permissions etc (similar to a grep in Linux for example)? Any starting points would be greatly appreciated, things like inter-app communication, converting code into text, searching through that text and reporting and the like.
I think the key might be using an app to inspect a Manifest file of another for permissions settings etc. I've learnt that Dalvik compiled code has big differences to the original Android 'Java'. Is it even possible to use an app to read the Manifest file of another app?

If u use Android Studio try 'code inspect' , 'code analyze'.

how to setup details about an android app?

i have used eclipse, android sdk and phonegap to create a small application. I give it a test and create a test.apk package.
What i ma wondering is where can i set up some details about this app, like who made it, the app name, the version, an icon maybe, any other things i might need to setup.
I have a AndroidManifest.xml file and when i open it i get a nice gui but i don't know what to modify there
Im not sure what i need to set up and even if i need to.
A good tutorial is much appreciated. Thanks

You can set most of those things in the manifest file. If you want to include this information in your code, add license headers in all your classes, use java-doc etc.
If you want this information to be accessible in your app like from 'About' button, you have to handle it yourself.
Take a look at this example.

This details are to be filled when you upload it to android market. I dont think you set them in AndroidManifest.xml ! you can see the xml code , by clicking on the "source code" tab just below the UI .

Here's a tutorial that describes managing AndroidManifest.xml, the app name and icons from our AppLaud Eclipse plugin for PhoneGap Android.

How do I see the core Android classes?

I am trying to look inside a couple of Android core classes to see about overriding some methods. I have looked into getting the Android source code, but the process described on the Android dev site is all about installing and setting up some kind of development environment. This is not necessary to me. I just want to open a class or two in a text editor and look at its contents. Does anyone know if this is possible without going through the multitude of steps described on the Android dev forums?

The easiest way is to use Google Code Search. You just have to try a search like Activity.java android and you can see the source code of that class. It even has an outline inspector:

You can download the entire source with git our just look it up as a reference on the git site. Here is a link to the sdk code:
https://android.googlesource.com/platform/frameworks/base

Another option is to use http://grepcode.com/ and perform a search such as "android ViewGroup". I've really enjoyed the style of using grepcode.