Java Reference
In-Depth Information
In Listing 7-4 we see that
ImageSequenceView
extends
Group
, and it takes a single
imageSequence
when
created. The
init
function creates an
ImageView
for each
Image
in the
ImageSequence
. Each
ImageView
is
translated so its center is at 0.0 of the
ImageSequenceView
and set to be invisible. The
ImageViews
are
centered for two reasons: First, I used this class in a game, and knowing the center is more convenient in
terms of game logic. Second, if the
Images
are not all the same size, I want them aligned by their centers.
The
ImageViews
are set to invisible (
visible: false
) because only one image will be visible at a time, so it
makes sense to start them all invisible. Each
ImageView
is then inserted into the
content
of the
ImageSequenceView
.
The last thing
init
does is call the function
updateImage
. Note that
updateImage
is also called when
the variable
currentImage
is changed. The function
updateImage
coordinates which
ImageView
in the
content
is visible. This is done by finding the last
ImageView
that was visible, setting it to invisible, and
then setting the
ImageView
at the index of
currentImage
to visible.
Figure 7-8 shows a graph diagram for an
ImageSequenceView
.
Figure 7-8.
Node graph of an ImageSequenceView
The circle is the
ImageSequenceView
itself. The big squares are the
ImageViews
that are contained in
the
content
of the
ImageSequenceView
, which extends
Group
. The third big square from the left, shown in
a darker color, is the currently displayed
ImageView
.
Further Considerations
In this chapter,
ImageSequenceViews
are used to represent cyclical animations, but this is not their only
function. They could also be used to store all of the different images that comprise a sprite in a game, for
example. Consider a character from a side-scrolling game: The character will require five or six images to
represent the sprite when it is walking, at least one to represent it when it is just standing still, and
perhaps three or four more for each action it performs. An
ImageSequenceView
could be used to store all
of these images, and changing how the sprite looks would be as simple as setting
currentImage
to the
correct value.
