| java.lang.Object
 javax.microedition.lcdui.game.LayerManager
| LayerManager | | public class LayerManager (Code) | | The LayerManager manages a series of Layers. The LayerManager simplifies
the process of rendering the Layers that have been added to it by
automatically rendering the correct regions of each Layer in the
appropriate order.
The LayerManager maintains an ordered list to which Layers can be appended,
inserted and removed. A Layer's index correlates to its z-order; the layer
at index 0 is closest to the user while a the Layer with the highest index
is furthest away from the user. The indices are always contiguous; that
is, if a Layer is removed, the indices of subsequent Layers will be
adjusted to maintain continuity.
The LayerManager class provides several features that control how the
game's Layers are rendered on the screen.
The view window controls the size of the visible region and its
position relative to the LayerManager's coordinate system. Changing the
position of the view window enables effects such as scrolling or panning
the user's view. For example, to scroll to the right, simply move the view
window's location to the right. The size of the view window controls how
large the user's view will be, and is usually fixed at a size that is
appropriate for the device's screen.
In this example, the view window is set to 85 x 85 pixels and is located at
(52, 11) in the LayerManager's coordinate system. The Layers appear at
their respective positions relative to the LayerManager's origin.
The
LayerManager.paint(Graphics,int,int) method includes an (x,y) location
that controls where the view window is rendered relative to the screen.
Changing these parameters does not change the contents of the view window,
it simply changes the location where the view window is drawn. Note that
this location is relative to the origin of the Graphics object, and thus
it is subject to the translation attributes of the Graphics object.
For example, if a game uses the top of the screen to display the current
score, the view window may be rendered at (17, 17) to provide enough space
for the score.
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| Constructor Summary | |
| public | LayerManager()
Creates a new LayerManager. |
| Method Summary | |
| public void | append(Layer l)
Appends a Layer to this LayerManager. | | public Layer | getLayerAt(int index)
Gets the Layer with the specified index. | | public int | getSize()
Gets the number of Layers in this LayerManager. | | public void | insert(Layer l, int index)
Inserts a new Layer in this LayerManager at the specified index. | | public void | paint(Graphics g, int x, int y)
Renders the LayerManager's current view window at the specified
location.
The LayerManager renders each of its layers in order of descending
index, thereby implementing the correct z-order. | | public void | remove(Layer l)
Removes the specified Layer from this LayerManager. | | public void | setViewWindow(int x, int y, int width, int height)
Sets the view window on the LayerManager.
The view window specifies the region that the LayerManager draws when
its
LayerManager.paint method is called. |
| LayerManager | | public LayerManager()(Code) | | Creates a new LayerManager.
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| append | | public void append(Layer l)(Code) | | Appends a Layer to this LayerManager. The Layer is appended to the
list of existing Layers such that it has the highest index (i.e. it
is furthest away from the user). The Layer is first removed
from this LayerManager if it has already been added.
See Also: LayerManager.insert(Layer,int)
See Also: LayerManager.remove(Layer)
Parameters:
l - the Layer to be added
throws:
NullPointerException - if the Layer isnull |
| getLayerAt | | public Layer getLayerAt(int index)(Code) | | Gets the Layer with the specified index.
Parameters:
index - the index of the desired Layer the Layer that has the specified index
throws:
IndexOutOfBoundsException - if the specifiedindex is less thanzero, or if it is equal to or greater than the number of Layers addedto the this LayerManager |
| getSize | | public int getSize()(Code) | | Gets the number of Layers in this LayerManager.
the number of Layers |
| insert | | public void insert(Layer l, int index)(Code) | | Inserts a new Layer in this LayerManager at the specified index.
The Layer is first removed from this LayerManager if it has already
been added.
See Also: LayerManager.append(Layer)
See Also: LayerManager.remove(Layer)
Parameters:
l - the Layer to be inserted
Parameters:
index - the index at which the new Layer isto be inserted
throws:
NullPointerException - if the Layer isnull
throws:
IndexOutOfBoundsException - if the index is less than0 orgreater than the number of Layers already added to the this orif the index is greater than the number of Layers already addedto this LayerManager minus one and the Layer has already been addedto this LayerManagerLayerManager |
| paint | | public void paint(Graphics g, int x, int y)(Code) | | Renders the LayerManager's current view window at the specified
location.
The LayerManager renders each of its layers in order of descending
index, thereby implementing the correct z-order. Layers that are
completely outside of the view window are not rendered.
The coordinates passed to this method determine where the
LayerManager's view window will be rendered relative to the origin
of the Graphics object. For example, a game may use the top of the
screen to display the current score, so to render the game's layers
below that area, the view window might be rendered at (0, 20). The
location is relative to the Graphics object's origin, so translating
the Graphics object will change where the view window is rendered on
the screen.
The clip region of the Graphics object is intersected with a region
having the same dimensions as the view window and located at (x,y).
The LayerManager then translates the graphics object such that the
point (x,y) corresponds to the location of the viewWindow in the
coordinate system of the LayerManager. The Layers are then rendered
in the appropriate order. The translation and clip region of the
Graphics object are restored to their prior values before this method
returns.
Rendering is subject to the clip region and translation of the Graphics
object. Thus, only part of the specified view window may be rendered
if the clip region is not large enough.
For performance reasons, this method may ignore Layers that are
invisible or that would be rendered entirely outside of the Graphics
object's clip region. The attributes of the Graphics object are not
restored to a known state between calls to the Layers' paint methods.
The clip region may extend beyond the bounds of a Layer; it is the
responsibility of the Layer to ensure that rendering operations are
performed within its bounds.
See Also: LayerManager.setViewWindow
Parameters:
g - the graphics instance with which to draw the LayerManager
Parameters:
x - the horizontal location at which to render the view window,relative to the Graphics' translated origin
Parameters:
y - the vertical location at which to render the view window,relative to the Graphics' translated origin
throws:
NullPointerException - if g is null |
| setViewWindow | | public void setViewWindow(int x, int y, int width, int height)(Code) | | Sets the view window on the LayerManager.
The view window specifies the region that the LayerManager draws when
its
LayerManager.paint method is called. It allows the developer to
control the size of the visible region, as well as the location of the
view window relative to the LayerManager's coordinate system.
The view window stays in effect until it is modified by another call
to this method. By default, the view window is located at (0,0) in
the LayerManager's coordinate system and its width and height are both
set to Integer.MAX_VALUE.
Parameters:
x - the horizontal location of the view window relative to theLayerManager's origin
Parameters:
y - the vertical location of the view window relative to theLayerManager's origin
Parameters:
width - the width of the view window
Parameters:
height - the height of the view window
throws:
IllegalArgumentException - if the width orheight is less than 0 |
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