J2ME转换器程序不接受用户输入

Question

I am having problems with my converter program not accepting the value the user inputs. Everything seems so right but the result is always as if the user entered nothing. If anyone can just point me in the right direction I would greatly appreciate it!

my project consists of 2 files (1 midlet and 1 class).

code was too long to post on this forum so I uploaded the zip.

Edit hosted here now should be cleaner: removed I can't really narrow it down to a small piece of code because it could be any number of things which I have already tried. I know its asking quite a bit but the code isn't insanely long. I'd be extremely grateful if anyone could take a look.

edit 2: the file seems to be trying to download an image... here is the code in another forum i posted in but got no answers.: http://www.codingforums.com/showthread.php?p=1024059#post1024059

edit 3: here is where I think the problem lies in the code:` public double customForm (String fName) { ui_form = new Form(fName);

    ui_form.addCommand(Convert);
    ui_form.addCommand(Back);

    display.setCurrent(ui_form);

num = new TextField("Enter the number of units you would like to convert", "", MAX_CHARS, TextField.ANY);
    ui_form.append(num);
    ui_form.setCommandListener(this);

    /***********************/
    /* THIS IS NOT WORKING*/
   // str = num.getString();
    str = "The number is: " + num.getString();
    try
    {
    numUnits = Double.parseDouble(str);
    }
    catch (NumberFormatException nfe)
    {
    }
    finally
    {
        return numUnits;
    }

    //return str;
}

`

but you will probably need to look at the rest of the code to see where the problem lies. this is just the root i think

Answer 1

You cannot read the text field right after it has been added to a form. It looks like you assumed the num.getString() method to block until there's user input - this is not the case. User input is provided asynchronously , ie you should read the text field's content in response to a user command, somewhere in the commandAction() method (in your case when the Convert command has been issued by the user).

Handling user events asynchronously is a core pattern in GUI development. In this regard I recommend to read some example code for command handling in JavaME, for instance this or this .