Pro Android Media: Developing Graphics, Music, Video, and Rich Media Apps for Smartphones and Tablets

Canvas Drawing

We know from the last chapter that we can draw Bitmap images on a Canvas object. That's not it for the Canvas class in Android, though. It also supports vector and text drawing. We can use a Canvas object either with Bitmap objects, as we did in the last chapter, or with Views. To start, we'll use a Canvas to create or alter a Bitmap and then move on to doing some very simple Canvas-based animation using a View.

Bitmap Creation

In the same manner we used previously, we can construct a Canvas object from a mutable Bitmap. To create a mutable Bitmap, a Bitmap that can be modified, we have to supply a width, a height, and a configuration. The configuration is generally a constant value defined in the Bitmap.Config class.

The following ...