Advice for developing apps

Well if you known Eclipse IDE at all you should just be able to get it working like this:

http://developer.android.com/sdk/installing/installing-adt.html

If you have the ability to run OSX you can get xcode up and running then you have the ability to configure development for iOS apps...
https://developer.apple.com/library/ios/#referencelibrary/GettingStarted/RoadMapiOS/chapters/Introduction.html

From my personal experience I found that with a background in C/C++ Java..etc...that Android development seemed to be easier and less constricting than developing for iOS with their xcode-only development and using Objective C to me seemed like taking C++ and adding a lot of extra symbols that make it difficult to go from the Java / C++ way of substantiation of objects...etc. The syntax is really confusing.

Also with the lock down of xcode to OSX only, if you don't have a Mac or don't see yourself ever buying one, it will become difficult to develop iOS.

I would say Android also isn't without its flaws of fragmentation that causes developers a lot of hair-pulling. The deal is you lock down your app to a range of versions of Android however that might not support all hardware or target audience intended.

here is more about ios vs. android development:
http://mobiledevices.about.com/od/kindattentiondevelopers/tp/Android-Os-Vs-Apple-Ios-Which-Is-Better-For-Developers.htm

Well I would say if you know Java well enough to get a basic app done I would say studying how GUI's work with event-driven driver. Meaning you press a button and something happens and then press another button and something else happens. On any mobile device a GUI is required for an application. Having a good design of how you want them to look and feel might take time, experience, and feedback. However, you can learn XML to help to rapidly develop GUI's for Android.

Android allows you to use XML to easily develop the GUI. Now what is great is the Android Development Tools (ADT) plugin for Eclipse IDE allows you to create a very fast GUI. However the drag and drop approach only gets you so far. A lot of what you need to learn is through learning XML, and learning design architecture such as Model-View-Controller (MVC) Arch. The idea is that when you have a GUI and your model changes your GUI or "View" should reflect said changes. Also when you input data into text boxes or press buttons on the GUI "View" your Model should have the respective data modified to reflect changes required.

Another thing is from the ground up make sure you can make your code extensible. Meaning modular and have the ability to be fluid and dynamic in the ability to change in the never ending uphill battle of the developer, and the changing API and feedback of the end-users. The power of Java is in its ability to, if utilized correctly and planned out, create extensible code that for the most part can stand the changes of the times. The best thing you can do is to plan ahead by allowing your application to only require modular additions to existing code for extra functionality requested by the end-users, or to change just the data structure when new API is released that allows for better performance. With the approach of extensible design of your code your project can have the ability to put all your eggs into one basket knowing that when the basket gets old you can transport the existing placement and structure of the eggs into a new basket, or when you need to add another egg to the basket.

Resources:

Model-View-Controller: http://en.wikipedia.org/wiki/Model%E2%80%93view%E2%80%93controller

Here is Android's Best Practices: http://developer.android.com/guide/practices/index.html

XML Android GUI: http://developer.android.com/guide/topics/ui/declaring-layout.html

Useful Resource for Best Practices in Java: http://www.javapractices.com/home/HomeAction.do
Edited by adramalech707 - 11/8/12 at 2:44pm

If you want to do Java/android start here. I find google documentation is always well written and they have tonnes of example code.

GL