j2me文本自动换行

一、Midlet框架
import javax.microedition.lcdui.Display;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

import demo.MainCanvas;


public class AutoAjustMidlet extends MIDlet {

	public MainCanvas m_MainCanvas;
	public AutoAjustMidlet() {
		super();
	}
	protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
		m_MainCanvas.Stop();
	}
	protected void pauseApp() {
		m_MainCanvas.Stop();
	}
	protected void startApp() throws MIDletStateChangeException {
		m_MainCanvas = new MainCanvas();
		Display.getDisplay(this).setCurrent(m_MainCanvas);
	}
}




二、辅助类
package demo;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;


public class TextAjust {
	//功能: 		计算需要换行的位置 
	//str:		需要显示的文字 
	//font：		文字的字体 
	//linewd：	每行的宽度限制 
	static public int ChangLine(String str, Font font, int linewd )
	{ 
		int wd = 0;
		char ch;
		for (int i = 0; i < str.length(); i++) 
		{ 
			ch = str.charAt(i);
			if (ch == '\n')
				return i + 1;
			 
			wd += font.charWidth(ch);
			if (wd > linewd)
				return i;
		}
		return 0;
	}


	//功能: 		分行显示字符串
	//g:		当前显示的缓冲
	//strText:	显示的字符串
	//linewd:	每行的宽度限制
	//x,y:		字符串左上角显示的位置
	//yDis:     显示文字时每行间隔的距离
	static public void AjustDrawString( Graphics g, String strText, 
			int linewd, int x, int y, int yDis )
	{
		String subStr;
		int nPos; //需要换行的位置
		while (true)
		{
			nPos = ChangLine(strText, g.getFont(), linewd );
			if (nPos == 0)
			{
				g.drawString( strText, x, y, 0);
				break;
			}
			else
			{
				if (strText.charAt(nPos - 1) == '\n' )
					subStr = strText.substring(0, nPos - 1);
				else
					subStr = strText.substring(0, nPos);
				g.drawString( subStr, x, y, 0);
				strText = strText.substring(nPos, strText.length());
				y = y + yDis;
			}
		}
	}
}

三、GameCanvas框架：
package demo;
import javax.microedition.lcdui.Font;
import javax.microedition.lcdui.Graphics;
import javax.microedition.lcdui.game.GameCanvas;


public class MainCanvas extends GameCanvas implements Runnable{
	private boolean	m_bRunning;				//控制项目运行
	public int	m_nWidth = 50;					//显示宽度
	public Font m_Font;							//存储字体
	public MainCanvas(){
		super(true);
		//创建字体，如果创建失败，则采用系统默认字体
		try{
			m_Font 	= Font.getFont(Font.FACE_SYSTEM, 
							Font.STYLE_PLAIN, Font.SIZE_LARGE );
		}catch(Exception e){
			m_Font  = Font.getDefaultFont();
		}
		Start();								//启动线程
	}


	public void Start(){
		m_bRunning = true;
		Thread thread = new Thread(this);		//分配新线程
		thread.start();							//线程启动
	}
	public void run() {						//新线程自动调用此方法
		//获得系统当前时间,并将时间换算成毫秒
		long T1 = System.currentTimeMillis();
		long T2 = T1;
		while(m_bRunning){
			T2 = System.currentTimeMillis();
			if( T2 - T1 > 100 ){			//间隔100毫秒
				T1 = T2;
				Input();
				Logic();
				Paint();
			}
		}
	}


	public void Stop(){						//终止游戏
		m_bRunning = false;
	}


	public void Input(){
		int keyStates = getKeyStates();			//获取当前按键状态
		//如果按下方向键的上键，则调整显示宽度		
		if( ( keyStates & GameCanvas.UP_PRESSED ) != 0 )	
			m_nWidth = m_nWidth +10; 		
		//如果按下方向键的下键，则调整显示宽度		
		if( ( keyStates & GameCanvas.DOWN_PRESSED ) != 0 )			
			m_nWidth = m_nWidth -10;
	}


	public void Logic(){
	}


	public void Paint(){
		Graphics g = getGraphics();
		//用黑色清屏
		g.setColor(0x00000000);
		g.fillRect( 0, 0, getWidth(), getHeight() );
		g.setFont(m_Font);
		g.setColor(0x00FFFFFF);
		TextAjust.AjustDrawString(g, 
				"我要自动换行我要自动换行我要自动换行我要自动换行",
				m_nWidth, 20, 20, 15 );
		
		flushGraphics();
	}
}