What your mother didn't tell you about Custom Views

Who I am?

Raimon Rfols@rrafols+RaimonRafolsMontanehttp://blog.rafols.org

Software Engineering ManagerImagination Technologies

@ImaginationPRimgtec.com

Custom ViewsMotivation

Why?

Advantages?

Benefits?

Should we use them on all kind of projects?

Or should we prioritise the use of standard components only?

Isn't it too much effort?

DesignProgrammingTesting

Let's build one Custom View!

Is that all?

What's the result?

Layout parameters

MATCH_PARENT

WRAP_CONTENT

SPECIFIC SIZE

MeasureSpec.AT_MOST

MeasureSpec.EXACTLY

MeasureSpec.UNSPECIFIED

What's the mapping between these values?

WIDTH: EXACTLYHEIGHT: EXACTLY

WIDTH: EXACTLYHEIGHT: AT_MOST

WIDTH: EXACTLYHEIGHT: UNSPECIFIED

Parametrise

Define parameters ina xml resource fileattrs.xml

Be nice - Always recycle!

Tips

Don't create Paint objects on onDraw. As a rule of thumb don't allocate memory on draw methods.

API support & limitations

What could be done?

Detect version on runtime and adapt dynamically

?

http://developer.android.com/guide/topics/graphics/hardware-accel.html

@rrafolshttp://blog.rafols.org