HelloWorld:(

[rainver]

谁能给个HelloWorld程序啊？
这个编译通过了但是在模拟器里显示有问题，点launch时抛出null Exception
java.lang.NullPointer Exception
我用的是jdk1.4.2和wkt1.0.4运行示例程序没有问题，不会是配置错了吧？？

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class HelloWorld extends MIDlet implements CommandListener
{
private Display display;
private Form props;

private Command exitCommand = new Command("Exit", Command.EXIT, 1);

public HelloWorld()
{
display = Display.getDisplay(this);
}

public void startApp()
{
props = new Form("Hello World");
props.append("Hello World!\n");

props.addCommand(exitCommand);
props.setCommandListener(this);
display.setCurrent(props);
}

public void commandAction(Command c, Displayable s)
{
if (c == exitCommand)
{
destroyApp(false);
notifyDestroyed();
}
}

public void destroyApp(boolean unconditional)
{
}

public void pauseApp()
{
display.setCurrent(null);
props = null;
}

}
各位帮帮忙，谢谢了先：）

[realmon]

初级

[snomile]

我运行没问题， 呵呵。
你试试把
public HelloWorld()
{
display = Display.getDisplay(this);
}

里面的display = Display.getDisplay(this); 移动到startApps那里，我想可能是因为类构造函数没有执行完的时候是不允许使用Display.getDisplay(this)的

[mercuryking]

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

public class HelloMIDlet extends MIDlet implements CommandListener
{
private Command exitCommand;
private Display display;
public HelloMIDlet()
{
display = Display.getDisplay(this);
exitCommand = new Command("Exit", Command.SCREEN, 2);
}
public void startApp()
{
TextBox t = new TextBox("Hello MIDlet", "Test string", 256, 0);
t.addCommand(exitCommand);
t.setCommandListener(this);
display.setCurrent(t);
}
public void pauseApp()
{
}
public void destroyApp(boolean unconditional)
{
}
public void commandAction(Command c, Displayable s)
{
if (c == exitCommand)
{
destroyApp(false);
notifyDestroyed();
}
}
}