scrollmidlet.java

来自「example2 众多JAVA实例源码...学习java基础的好帮手」· Java 代码 · 共 142 行

package opusmicro.demos.scalllist;

import java.util.Vector;

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

public class ScrollMIDlet extends MIDlet {
	public ScrollMIDlet() {}
	protected void destroyApp(boolean arg0) throws MIDletStateChangeException {}
	protected void pauseApp() {}
	protected void startApp() throws MIDletStateChangeException {
		ScrollCanvas sc = new ScrollCanvas();
		for(int i=0;i<25;i++){
			Item si = new Item("ITEM "+i);
//			si.height = 30 + i*2;
			sc.addChild(si);
		}
		Display.getDisplay(this).setCurrent(sc);
	}
}
class Item {
	private String text;
	int height=26;
	public Item(String text){
		this.text = text;
	}
	public void paint(Graphics g, int x, int y, int w, int h, boolean focus){
		if(focus){
			g.setColor(0xffff);
		}else{
			g.setColor(0x10ff);
		}
//		g.fillRect(x, y, w, height);
		g.fillRect(x, y, w, h);
		if(text!=null){
			g.setColor(0);
			g.drawString(text, x+5, (y+Font.getDefaultFont().getHeight()/2), g.LEFT|g.TOP);
		}
	}
}
class ScrollCanvas extends Canvas{

	private int position = 0;
	Vector children = new Vector();
	private int start = 0;
	private int width, height;
	private Item item;
	private int scrollbarwidth = 6;
	private boolean positionchange;
	public ScrollCanvas(){
		width = getWidth();
		height = getHeight();
	}
	public void addChild(Item item){
		if(!children.contains(item)){
			children.addElement(item);
		}
	}
	void preposition(){
		if(position>0){
			position--;
		}
		positionchange = true;
		repaint();
		serviceRepaints();
	}
	void nextposition(){
		if(position<children.size()-1){
			position++;
		}
		positionchange = true;
		repaint();
		serviceRepaints();
	}
	public void keyPressed(int keyCode){
		int action = getGameAction(keyCode);
		switch(action){
			case Canvas.UP:
				preposition();
				break;
			case Canvas.DOWN:
				nextposition();
				break;
		}
	}
	public void keyRepeated(int keyCode){
		keyPressed(keyCode);
	}
	public void moveStart(){
		if ( positionchange) {
			positionchange = false;
			int positionStart = 0;
			int positionEnd = 0;
			for ( int i = start, stop = children.size() ; i < stop && i < position ; i++) {
				positionStart += ((Item) children.elementAt(i)).height;
			}
System.out.println("start "+start);			
System.out.println("position "+position);
System.out.println("positionStart "+positionStart);
			positionEnd = positionStart + ((Item) children.elementAt(position)).height;
			if ( positionStart <= 0) {
				start = position;
			}
			else if ( positionEnd > height) {
				for ( int i = start ; i <= position && i < children.size() && positionEnd > height ; i++) {
					start++;
					positionEnd -= ((Item) children.elementAt(i)).height;
				}
			}
		}
	}
	protected void paint(Graphics g) {
		int x=0, y=0;
		g.setColor(0x00aa12);
		g.fillRect(0, 0, width, height);
		int[] clip = {g.getClipX(),g.getClipY(),g.getClipWidth(),g.getClipHeight()};
		g.setClip(x, y, width, height);
		
		if(!children.isEmpty()){
			moveStart();
			for(int i=start;i<children.size()&&y<height;i++){
				item = ((Item)children.elementAt(i));
				item.paint(g, x, y, width-scrollbarwidth, 23, i==position);
				y += item.height;
				
			}
			if(start>0 || y>height){
				double scrollbarheight = Math.floor((height+.5)/children.size());
				int scrollbary = (int) Math.floor(scrollbarheight*position+.5);
				g.setColor(0);
				g.fillRect(width-scrollbarwidth, scrollbary, scrollbarwidth, (int)scrollbarheight);
			}
		}
		g.setClip(clip[0], clip[1], clip[2], clip[3]);
	}
	
}