grass.java

来自「用Java/C#开发手机程序及移动应用光盘代码。J2ME核心类及MIDlet类；」· Java 代码 · 共 63 行

import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

public class Grass extends TiledLayer {

	static int TILE_WIDTH = 20;
	static int[] FRAME_SEQUENCE = { 2, 3, 2, 4 };

	static int COLUMNS;
	static int CYCLE = 5;
	static int TOP_Y;

	int mySequenceIndex = 0;
	int myAnimatedTileIndex;

	// 计算有多少列
	static int setColumns(int screenWidth) {
		COLUMNS = ((screenWidth / 20) + 1)*3;
		return(COLUMNS);
	}
	/**
	 * 构造方法，其中创建了动态图
	 */
	public Grass() throws Exception {
		super(setColumns(JumpCanvas.DISP_WIDTH), 1, 
			Image.createImage("/icons/grass.png"), 
			TILE_WIDTH, TILE_WIDTH);
		TOP_Y = JumpManager.DISP_HEIGHT - TILE_WIDTH;
		setPosition(0, TOP_Y);
		myAnimatedTileIndex = createAnimatedTile(2);
		for(int i = 0; i < COLUMNS; i++) {
			if((i % CYCLE == 0) || (i % CYCLE == 2)) {
				setCell(i, 0, myAnimatedTileIndex);
			} else {
				setCell(i, 0, 1);
			}
		}
	}

	/**
	 * 重置
	 */
	void reset() {
		setPosition(-(TILE_WIDTH*CYCLE), TOP_Y);
		mySequenceIndex = 0;
		setAnimatedTile(myAnimatedTileIndex, 
			FRAME_SEQUENCE[mySequenceIndex]);
	}

	/**
	 * 步进
	 */
	void advance(int tickCount) {
		if(tickCount % 2 == 0) { // 使其略慢一点
			mySequenceIndex++;
			mySequenceIndex %= 4;
			setAnimatedTile(myAnimatedTileIndex, 
				FRAME_SEQUENCE[mySequenceIndex]);
		}
	}

}