多个canvas切换时，屏幕显示问题

[lalio77]

写了类似这样的结构：
{

public class myj2me extends MIDlet {
         Display display.....//初始化过程略去
         //构造函数中
	canvas1 can1 = new canvas1(this);
	canvas2 can1 = new canvas2(this);
         public void startApp(){display.setCurrent(can1);}
         public void setcanvas1(){display.setCurrent(can1);}
         public void setcanvas2(){display.setCurrent(can2);}
}
class canvas1 extends Canvas implements CommandListener {
	myj2me j2me;
	public canvas1(myj2me my_j2me) {
		j2me = my_j2me;
	}
	public void commandAction(Command cmd,Displayable dis){
			if(cmd==...){
			         j2me.setcanvas2();
			}
		}
}
class canvas2 extends Canvas implements CommandListener {
	myj2me j2me;

	public canvas2(myj2me my_j2me) {
		j2me = my_j2me;
	}
	public void commandAction(Command cmd,Displayable dis){
			if(cmd==...){
			         j2me.setcanvas3();
			}
		}
}

}

初学j2me，想当然的就这样写了，果然有问题，若先显示can1,从can1通过调用setcanvans2()切换到can2的时候屏幕不会刷新，也就是can1的界面还在。

请教一下要如何才能刷新屏幕呢？

[lalio77]

setcanvas()有贴出来，在myj2me类中；
paint函数只是一些简单的drawstring，本来就是用来测试的，每个canvas都有自己的paint，在不同的地方写字符串

[lalio77]

嗯。。网上都说用多个canvas不好。。

[softice_]

setcanvans代码贴出来看看

[softice_]

还有paint()代码

[sandeel]

是你的Canvas2的对象错了：

canvas1 can1 = new canvas1(this);
canvas2 can1 = new canvas2(this); ----------------这一行

修改为：
canvas1 can1 = new canvas1(this);
canvas2 can2 = new canvas2(this);

就可以了

[sandeel]

import javax.microedition.lcdui.Canvas;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Graphics;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;



public class Canvas123 extends MIDlet {
Display display;
Command cmdChange = new Command("change",Command.SCREEN,1);
//初始化过程略去
//构造函数中
canvas1 can1 = new canvas1(this);
canvas2 can2 = new canvas2(this);
public void startApp(){
display = Display.getDisplay(this);
display.setCurrent(can1);
}
public void setcanvas1(){display.setCurrent(can1);}
public void setcanvas2(){display.setCurrent(can2);}
protected void destroyApp(boolean arg0)
throws MIDletStateChangeException {
// TODO Auto-generated method stub

}
protected void pauseApp() {
// TODO Auto-generated method stub

}
}

class canvas1 extends Canvas implements CommandListener {
Canvas123 j2me;
Command cmdChange = new Command("change",Command.SCREEN,1);

public canvas1(Canvas123 my_j2me) {
j2me = my_j2me;
addCommand(cmdChange);
setCommandListener(this);
}
public void commandAction(Command cmd,Displayable dis){
if(cmd==cmdChange){
j2me.setcanvas2();
}
}
protected void paint(Graphics g) {
// TODO Auto-generated method stub
g.setColor(255, 255, 255);
g.drawString("Hello1", 0, 0, Graphics.LEFT|Graphics.TOP);
}
}
class canvas2 extends Canvas implements CommandListener {
Canvas123 j2me;
Command cmdChange = new Command("change",Command.SCREEN,1);
public canvas2(Canvas123 my_j2me) {
j2me = my_j2me;
addCommand(cmdChange);
setCommandListener(this);
}
public void commandAction(Command cmd,Displayable dis){
if(cmd==cmdChange){
j2me.setcanvas1();

}
}
protected void paint(Graphics g) {
// TODO Auto-generated method stub
g.setColor(255, 255, 255);
g.drawString("Hello2", 0, 0, Graphics.LEFT|Graphics.TOP);

}
}