Examples of javax.microedition.lcdui.game.TiledLayer
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javax.microedition.lcdui.game.TiledLayer
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 {@link #setStaticTileSet} 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 {@link #createAnimatedTile}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 {@link #setAnimatedTile}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 {@link #setCell} and{@link #fillCells}. 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 usingsetAnimatedTile(-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.
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