javax.microedition.lcdui.game
Class TiledLayer

java.lang.Object
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  +--javax.microedition.lcdui.game.Layer
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        +--javax.microedition.lcdui.game.TiledLayer

public class TiledLayer

extends Layer

A TiledLayer is a visual element composed of a grid of cells that can be filled with a set of tile images. This class allows large virtual layers to be created without the need for an extremely large Image. This technique is commonly used in 2D gaming platforms to create very large scrolling backgrounds,

Tiles

The tiles used to fill the TiledLayer's cells are provided in a single Image object which may be mutable or immutable. The Image is broken up into a series of equally-sized tiles; the tile size is specified along with the Image. As shown in the figure below, the same tile set can be stored in several different arrangements depending on what is the most convenient for the game developer.

Each tile is assigned a unique index number. The tile located in the upper-left corner of the Image is assigned an index of 1. The remaining tiles are then numbered consecutively in row-major order (indices are assigned across the first row, then the second row, and so on). These tiles are regarded as static tiles because there is a fixed link between the tile and the image data associated with it.

A static tile set is created when the TiledLayer is instantiated; it can also be updated at any time using the setStaticTileSet(javax.microedition.lcdui.Image, int, int) method.

In addition to the static tile set, the developer can also define several animated tiles. An animated tile is a virtual tile that is dynamically associated with a static tile; the appearance of an animated tile will be that of the static tile that it is currently associated with.

Animated tiles allow the developer to change the appearance of a group of cells very easily. With the group of cells all filled with the animated tile, the appearance of the entire group can be changed by simply changing the static tile associated with the animated tile. This technique is very useful for animating large repeating areas without having to explicitly change the contents of numerous cells.

Animated tiles are created using the createAnimatedTile(int) method, which returns the index to be used for the new animated tile. The animated tile indices are always negative and consecutive, beginning with -1. Once created, the static tile associated with an animated tile can be changed using the setAnimatedTile(int, int) method.

Cells

The TiledLayer's grid is made up of equally sized cells; the number of rows and columns in the grid are specified in the constructor, and the physical size of the cells is defined by the size of the tiles.

The contents of each cell is specified by means of a tile index; a positive tile index refers to a static tile, and a negative tile index refers to an animated tile. A tile index of 0 indicates that the cell is empty; an empty cell is fully transparent and nothing is drawn in that area by the TiledLayer. By default, all cells contain tile index 0.

The contents of cells may be changed using setCell(int, int, int) and fillCells(int, int, int, int, int). Several cells may contain the same tile; however, a single cell cannot contain more than one tile. The following example illustrates how a simple background can be created using a TiledLayer.

In this example, the area of water is filled with an animated tile having an index of -1, which is initially associated with static tile 5. The entire area of water may be animated by simply changing the associated static tile using setAnimatedTile(-1, 7).

Rendering a TiledLayer

A TiledLayer can be rendered by manually calling its paint method; it can also be rendered automatically using a LayerManager object.

The paint method will attempt to render the entire TiledLayer subject to the clip region of the Graphics object; the upper left corner of the TiledLayer is rendered at its current (x,y) position relative to the Graphics object's origin. The rendered region may be controlled by setting the clip region of the Graphics object accordingly.

Since:

MIDP 2.0

Constructor Summary

TiledLayer(int columns, int rows, Image image, int tileWidth, int tileHeight)
Creates a new TiledLayer.

Method Summary

int	createAnimatedTile(int staticTileIndex) Creates a new animated tile and returns the index that refers to the new animated tile.
void	fillCells(int col, int row, int numCols, int numRows, int tileIndex) Fills a region cells with the specific tile.
int	getAnimatedTile(int animatedTileIndex) Gets the tile referenced by an animated tile.
int	getCell(int col, int row) Gets the contents of a cell.
int	getCellHeight() Gets the height of a single cell, in pixels.
int	getCellWidth() Gets the width of a single cell, in pixels.
int	getColumns() Gets the number of columns in the TiledLayer grid.
int	getRows() Gets the number of rows in the TiledLayer grid.
void	paint(Graphics g) Draws the TiledLayer.
void	setAnimatedTile(int animatedTileIndex, int staticTileIndex) Associates an animated tile with the specified static tile.
void	setCell(int col, int row, int tileIndex) Sets the contents of a cell.
void	setStaticTileSet(Image image, int tileWidth, int tileHeight) Change the static tile set.

Methods inherited from class javax.microedition.lcdui.game.Layer

getHeight, getWidth, getX, getY, isVisible, move, setPosition, setVisible

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TiledLayer

public TiledLayer(int columns,
                  int rows,
                  Image image,
                  int tileWidth,
                  int tileHeight)

Creates a new TiledLayer.

The TiledLayer's grid will be rows cells high and columns cells wide. All cells in the grid are initially empty (i.e. they contain tile index 0). The contents of the grid may be modified through the use of setCell(int, int, int) and fillCells(int, int, int, int, int).

The static tile set for the TiledLayer is created from the specified Image with each tile having the dimensions of tileWidth x tileHeight. The width of the source image must be an integer multiple of the tile width, and the height of the source image must be an integer multiple of the tile height; otherwise, an IllegalArgumentException is thrown;

The entire static tile set can be changed using setStaticTileSet(Image, int, int). These methods should be used sparingly since they are both memory and time consuming. Where possible, animated tiles should be used instead to animate tile appearance.

Parameters:

columns - the width of the TiledLayer, expressed as a number of cells

rows - the height of the TiledLayer, expressed as a number of cells

image - the Image to use for creating the static tile set

tileWidth - the width in pixels of a single tile

tileHeight - the height in pixels of a single tile

Throws:

NullPointerException - if image is null

IllegalArgumentException - if the number of rows or columns is less than 1

IllegalArgumentException - if tileHeight or tileWidth is less than 1

IllegalArgumentException - if the image width is not an integer multiple of the tileWidth

IllegalArgumentException - if the image height is not an integer multiple of the tileHeight

Method Detail

createAnimatedTile

public int createAnimatedTile(int staticTileIndex)

Creates a new animated tile and returns the index that refers to the new animated tile. It is initially associated with the specified tile index (either a static tile or 0).

The indices for animated tiles are always negative. The first animated tile shall have the index -1, the second, -2, etc.

Parameters:

staticTileIndex - the index of the associated tile (must be 0 or a valid static tile index)

Returns:

the index of newly created animated tile

Throws:

IndexOutOfBoundsException - if the staticTileIndex is invalid

setAnimatedTile

public void setAnimatedTile(int animatedTileIndex,
                            int staticTileIndex)

Associates an animated tile with the specified static tile.

Parameters:

animatedTileIndex - the index of the animated tile

staticTileIndex - the index of the associated tile (must be 0 or a valid static tile index)

Throws:

IndexOutOfBoundsException - if the staticTileIndex is invalid

IndexOutOfBoundsException - if the animated tile index is invalid

See Also:

getAnimatedTile(int)

getAnimatedTile

public int getAnimatedTile(int animatedTileIndex)

Gets the tile referenced by an animated tile.

Returns the tile index currently associated with the animated tile.

Parameters:

animatedTileIndex - the index of the animated tile

Returns:

the index of the tile reference by the animated tile

Throws:

IndexOutOfBoundsException - if the animated tile index is invalid

See Also:

setAnimatedTile(int, int)

setCell

public void setCell(int col,
                    int row,
                    int tileIndex)

Sets the contents of a cell.

The contents may be set to a static tile index, an animated tile index, or it may be left empty (index 0)

Parameters:

col - the column of cell to set

row - the row of cell to set

tileIndex - the index of tile to place in cell

Throws:

IndexOutOfBoundsException - if there is no tile with index tileIndex

IndexOutOfBoundsException - if row or col is outside the bounds of the TiledLayer grid

See Also:

getCell(int, int), fillCells(int, int, int, int, int)

getCell

public int getCell(int col,
                   int row)

Gets the contents of a cell.

Gets the index of the static or animated tile currently displayed in a cell. The returned index will be 0 if the cell is empty.

Parameters:

col - the column of cell to check

row - the row of cell to check

Returns:

the index of tile in cell

Throws:

IndexOutOfBoundsException - if row or col is outside the bounds of the TiledLayer grid

See Also:

setCell(int, int, int), fillCells(int, int, int, int, int)

fillCells

public void fillCells(int col,
                      int row,
                      int numCols,
                      int numRows,
                      int tileIndex)

Fills a region cells with the specific tile. The cells may be filled with a static tile index, an animated tile index, or they may be left empty (index 0).

Parameters:

col - the column of top-left cell in the region

row - the row of top-left cell in the region

numCols - the number of columns in the region

numRows - the number of rows in the region

tileIndex - the Index of the tile to place in all cells in the specified region

Throws:

IndexOutOfBoundsException - if the rectangular region defined by the parameters extends beyond the bounds of the TiledLayer grid

IllegalArgumentException - if numCols is less than zero

IllegalArgumentException - if numRows is less than zero

IndexOutOfBoundsException - if there is no tile with index tileIndex

See Also:

setCell(int, int, int), getCell(int, int)

getCellWidth

public final int getCellWidth()

Gets the width of a single cell, in pixels.

Returns:

the width in pixels of a single cell in the TiledLayer grid

getCellHeight

public final int getCellHeight()

Gets the height of a single cell, in pixels.

Returns:

the height in pixels of a single cell in the TiledLayer grid

getColumns

public final int getColumns()

Gets the number of columns in the TiledLayer grid. The overall width of the TiledLayer, in pixels, may be obtained by calling Layer.getWidth().

Returns:

the width in columns of the TiledLayer grid

getRows

public final int getRows()

Gets the number of rows in the TiledLayer grid. The overall height of the TiledLayer, in pixels, may be obtained by calling Layer.getHeight().

Returns:

the height in rows of the TiledLayer grid

setStaticTileSet

public void setStaticTileSet(Image image,
                             int tileWidth,
                             int tileHeight)

Change the static tile set.

Replaces the current static tile set with a new static tile set. See the constructor TiledLayer(int, int, Image, int, int) for information on how the tiles are created from the image.

If the new static tile set has as many or more tiles than the previous static tile set, the the animated tiles and cell contents will be preserve. If not, the contents of the grid will be cleared (all cells will contain index 0) and all animated tiles will be deleted.

Parameters:

image - the Image to use for creating the static tile set

tileWidth - the width in pixels of a single tile

tileHeight - the height in pixels of a single tile

Throws:

NullPointerException - if image is null

IllegalArgumentException - if tileHeight or tileWidth is less than 1

IllegalArgumentException - if the image width is not an integer multiple of the tileWidth

IllegalArgumentException - if the image height is not an integer multiple of the tileHeight

paint

public final void paint(Graphics g)

Draws the TiledLayer. The entire TiledLayer is rendered subject to the clip region of the Graphics object. The TiledLayer's upper left corner is rendered at the TiledLayer's current position relative to the origin of the Graphics object. The current position of the TiledLayer's upper-left corner can be retrieved by calling Layer.getX() and Layer.getY(). The appropriate use of a clip region and/or translation allows an arbitrary region of the TiledLayer to be rendered.

If the TiledLayer's Image is mutable, the TiledLayer is rendered using the current contents of the Image.

Overrides:

paint in class Layer

Parameters:

g - the graphics object to draw the TiledLayer

Throws:

NullPointerException - if g is null