Java Reference
In-Depth Information
greater z-values and indices. Alternatively, we can add a layer at a specific
index using the method:
public void insert(Layer l, int index);
To remove a layer from the list we use the method:
public void remove(Layer l);
We position a layer in the LayerManager 's coordinate system using
the setPosition() method. The contents of LayerManager are not
rendered in their entirety; instead, a view window is rendered using the
paint() method of the LayerManager :
public void paint(Graphics g, int x, int y);
The x and y arguments are used to position the view window on
the displayable object ( Canvas or GameCanvas ) upon which the Lay-
erManager is rendered. The size of the view window is set using this
public void setViewWindow(int x, int y, int width, int height);
The x and y values determine the position of the top left corner of
the rectangular view window in the coordinate system of the Layer-
Manager . The width and height arguments determine the width and
height of the view window and are usually set to a size appropriate for the
device's screen. By varying the x and y coordinates we can pan through
the contents of the LayerManager .
LayerManagerDemo Example
Our LayerManagerDemo example summarizes all Game API concepts
seen so far. It illustrates the use of a Sprite (for animating the hero),
a TiledLayer (for background construction), a LayerManager (for
scrolling the background), and a GameCanvas (for drawing it all). The
source code is too large to be included in this topic, so it is available for
download from the website. We highlight here some parts that show how
to use the Game API components.
In the constructor, we load the image resources used by our Tiled-
Layer and the Sprite (see Figures 2.6 and 2.8, respectively). We
create our game hero, using the Sprite constructor, then set the frame
sequence, which allows us to loop only to the frames that interest us. In
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