Core Concepts of Mobile Development.pdf

Core Concepts of Mobile Development
© Codename One 2017 all rights reserved

Core Concepts of Mobile Development
✦These are universal concepts & will serve you
whether you use Codename One or don’t
✦I will highlight the Codename One solution for
some of these as we go thru them
✦The goal of this presentation is to familiarize you
with what can/can’t be done on mobile devices
and why that’s the case

Density &
Resolution

Density vs. Resolution
✦Density: also known as DPI (Dots Per Inch) or PPI
(pixels or points per inch)
✦Density is confusing, unintuitive & might collide
with common sense
✦E.g. an iPhone 7+ has 1080x1920 pixel
resolution and a PPI of 401 for a 5 inch screen 
An iPad 4 has 1536x2048 pixels with a PPI of
264 on a 9.7 inch screen
✦Smaller devices can have higher resolutions!

✦Diﬀerences in density can be extreme a second
generation iPad has 132 PPI where modern
phones have PPI that crosses the 600 mark!
✦Low resolution images on high PPI devices will
look either small or pixelated
✦High resolution images on low PPI devices will
look huge, overscaled (artifacts) and will consume
too much memory

✦The first solution is multi-images, all OS’s support
the ability to define diﬀerent images for various
densities
✦We support multi-images directly in the designer
tool and CSS. This automatically scales the image
using a high quality desktop scaling algorithm so
the right sized images are available on the device
✦The second approach is vector graphics which
can take several forms

Vector Graphics
✦Fonts (text) is eﬀectively vector graphics. We can
use that text as icons using icon fonts.
Codename One has builtin support for icon fonts
as well as the material design icon font
✦Vector files - the most popular format in this area
is SVG but it has spotty on device performance.
Android provides a tool to convert SVG to vector
code, we might oﬀer something similar in the
future

Certificates &
Provisioning

Signing & Certificates
✦All mobile OS’s only accept signed content but
their philosophy on the matter diﬀers
✦Apple provides a certificate indicating that you are
approved by them as a developer
✦Google & Microsoft let anyone sign the app. They
verify your identity in the store signup. The
signature is used to make sure someone else
can’t push updates to your app

✦If you lose your Google certificate you won’t be
able to upload a new version of the app. This isn’t
something Google can fix easily as it is blocked
on the devices!
✦E.g. if you try to install an Android app on a device
where an app with the same package exists with
a diﬀerent certificate this will fail!
✦This problem is irrelevant for iOS, you can revoke
and generate a new certificate without a problem

✦iOS has two certificate types: Development &
Distribution
✦You use the development certificate only during
development and you can install an app built with the
development certificate
✦Distribution certificates only allow upload to the store,
you can’t install such an app on your phone
✦The app becomes valid after Apple signs it too (after
the verification process) and places it into iTunes

Provisioning (iOS)
✦iOS has two separate provisioning profiles to
match the two separate certificates
✦The provisioning profile includes data about the
certificate (so they are bound together) and
information about the app
✦The debug version includes the list of devices on
which the app can be installed
✦Both provisioning profiles include details about the
services used by the app e.g. iCloud, push etc.

Push Certificates (iOS)
✦Push notification allows us to send a message to
a device even when the app isn’t running
✦In order to communicate with the ipns push server
we need two separate certificates (production &
sandbox)
✦These are used at runtime from our server push
code and aren’t involved in the signing process

Sandbox &
Permissions

Application Sandbox
✦Apps installed on the device are “sandboxed” to a
specific area so they won’t harm the device or its
functionality
✦This means that some features require a
“permission” prompt and in some cases require
special flags in system files
✦The filesystem of mobile applications is restricted
so one application can’t access the files of
another application

Application Sandbox
✦Things that we would assume as intuitive such as
“file picker” or accessing the image folder don’t
work on devices!
✦Apps can communicate by requesting a URL or
using special API’s for inter-application
communication - those approaches are only
partially portable

Permission Systems
✦Apps need to request permission to use sensitive
capabilities e.g. Camera, Contacts etc.
✦Historically Android developers declared required
permissions & a user was asked about them on install.
Android 6 adopted an iOS like approach
✦iOS prompts the user for permission when accessing a
feature. Once the user makes a decision he can flip
the switch in the application setting page

Background
Processes

Background Processes
✦When iOS launched it didn’t have multi-tasking
✦Android allowed arbitrary code to run in the
background
✦iOS later added support for background
processes which don’t allow arbitrary code. An
app can declare a use case e.g.: track location,
download file, play music etc. then perform that
task alone in the background with heavy
restrictions!

Background Processes
✦Android 6 improved battery life considerably by
placing heavy restrictions on arbitrary background
code in a similar way to iOS
✦With Codename One we support many of the
various background mode use cases

What did we learn?
✦A better sense of some less intuitive aspects of
mobile development
✦Apps require a major shift in thinking when
compared to desktop or server development
✦Deployment is a challenge on iOS
✦Don’t lose the Android or Windows keys!

Thank You

Core Concepts of Mobile Development.pdf

Recommended

Recommended

More Related Content

Similar to Core Concepts of Mobile Development.pdf

Similar to Core Concepts of Mobile Development.pdf (20)

More from ShaiAlmog1

More from ShaiAlmog1 (20)

Recently uploaded

Recently uploaded (20)

Core Concepts of Mobile Development.pdf