Common Java problems when developing with Android

Software Engineering Large Practical

Common Java problems when coding for
Android and advice for dealing with them

Stephen Gilmore

School of Informatics, University of Edinburgh

October 24th, 2012

Stephen Gilmore Software Engineering Large Practical

Java problems

For some, developing for the Android platform might provide their
ﬁrst experience of working with a complex, modern Java API. This
may test your knowledge of the Java programming language,
especially with regard to features such as generics. The Android
APIs make use of generics throughout and so you will have to
know how to create and handle generic classes.


Raw types

Raw types are a backwards compatibility feature which allowed
new generic Java code to use old non-generic libraries and to allow
non-generic Java code to continue to compile and work on modern
Java versions. Raw types are not needed when working with the
Android API and your project should not contain them.


Common Java problems: raw types, 8 warnings


Quick ﬁx: a bad suggestion


Check the constructor documentation


Check the class documentation


What type of array are we adapting?


Type parameter added, 6 warnings


Raw type parameters

Raw types need special treatment in method headers when
instances of generic classes are being passed as parameters to
methods. A special syntax is used to specify when we do not know
the type of the parameter to the generic class.


Raw type in method header, 5 warnings


Consult the Java documentation


Adapter doesn’t work here


Adapter is an interface


T is not a class


Object: the goto class


T extends Adapter doesn’t work


“?” — the wild card parameter, 3 warnings


“Quick ﬁx” would have worked here


Same result


Working with the Java compiler

The Java compiler used Eclipse allows you to tune the level of
checking which your program receives during compilation. This
checking (“static analysis”) evaluates the correctness of your
program without executing it.

The default settings do not apply particularly strict checking. We
recommend tightening the default settings to detect errors in your
Java code which you may otherwise miss.


Setting Java compiler preferences


Changing defaults


Potential programming problems


Tighter checking


Bug found


Remembering and forgetting while developing

Leaving an empty block is a classic “I must remember to do that
later” error. By turning on stricter checking with the static
analysis tools in the Java compiler we get automatic reminders in
the form of Java problems. These will persist in our project until
we do go back and write the remaining code block.


Logging

As we have seen, the Android emulator occupies all of the screen
real estate of our virtual device, in order to allow us to test apps as
they will be used in practice. If we want to log informational
messages for our own purposes then we should use the Android
logging API.


Don’t forget to add logging . . .

ng

Common Java problems when developing with Android

More Related Content

What's hot

Viewers also liked

Similar to Common Java problems when developing with Android

More from Stephen Gilmore

Recently uploaded

Common Java problems when developing with Android