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Forms

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 Objective

To design, write, compile and test forms and the piece of code that handles user interaction.

 Concepts

Creating labelz, buttonz, fieldz...

If you're used to developing windowed apps for PC, Mac or any other platform, then designing your first Palm form shouldn't be a problem. PilRC User Manual is the doc to refer to, should you need more details. Basically, you will "write" the .rcp file using your favorite text editor, compile it, link it to the compiled source code of your app, and get a beautiful .prc file that you can hotsync to your device or run on POSE.

Positioning items on a form may use either absolute values (like 50, 100) or relative values (like CENTER, PREVBOTTOM+2). I'd suggest that relative mode be used as much as possible because it's more flexible and makes updates easier.

Writing the .rcp file

Here's the big picture.

Define all the IDs of your controls, buttons, etc in a .h file, which will be #included in both your .rcp and .c files. This .h makes sure that the app and the form(s) use the same resource IDs

In your editor, create the .rcp file, include the .h, and give your form the following structure:

FORM ID Form1 AT (2 2 156 156) USABLE MODAL HELPID Help1
BEGIN
  TITLE "Forms 1/4 (Modal)"

  LABEL "This is a label" AUTOID AT (CENTER 20) FONT 1
  BUTTON "Next" ID Next AT (CENTER PREVBOTTOM+10 AUTO AUTO) FRAME
  BUTTON "Exit" ID Exit AT (CENTER@120 PREVTOP AUTO AUTO)
END

This says that we want a form with just one label, a Next button and Exit button. Labels do not communicate with the app, so we don't assign them any ID, neither do we mention them in the .h file. On the other hand, buttons may send events to our app, or our app may want to change a button's setting. That's why buttons, controls, etc. will be assigned IDs in our .h file.

Writing code that handles form and control events

Here's the overview of who can send what event, and what should be done. Variable "e" is our event.

Sender Event Meaning Action
Form manager frmLoadEvent Form has been loaded FrmSetActiveForm(FrmInitForm(e.data.frmLoad.formID))
Form manager frmOpenEvent Form has been opened FrmDrawForm(...)
Control ctlSelectEvent User tapped control if (e.data.ctlSelect.controlID == Next)
...
if (e.data.ctlSelect.controlID == Exit)
...
Control ctlRepeatEvent User tapped control and maintained stylus on control if (e.data.ctlRepeat.controlID == Form3Minus)
...
if (e.data.ctlRepeat.controlID == Form3Plus)
...

This handler is part of the "endless" loop started in PilotMain.

 Exercise

Download the ZIP file.

In this app, not all controls will generate event. For the sake of simplicity, those controls will not have IDs.

In forms.h:

  • add ID Next (value 9001)
  • add ID Exit (value 9002)

In forms.rcp:

  • in Form1, assign value Forms 1/4 (Modal) to TITLE
  • give a position of CENTER 20 to the first label
  • give a position of CENTER@50 PREVBOTTOM+10 and a size of AUTO AUTO to "Next" button
  • define Exit button as follows: BUTTON "Exit" ID Exit AT (CENTER@120 PREVTOP AUTO AUTO)
  • in Form2, add a PUSHBUTTON "2nd" ID 2012 AT (CENTER@80 PREVTOP AUTO AUTO) GROUP 1
  • add the first checkbox: CHECKBOX "Unchecked" ID 2021 AT (CENTER@50 PREVBOTTOM+2 AUTO AUTO)
  • in Form3, add a POPUPTRIGGER "Continent" ID 2040 AT (CENTER@40 PREVBOTTOM+2 AUTO AUTO)
  • add a popup list like this: LIST "Europe" "America" "Asia" "Africa" "Oceania" ID 2041 AT (PREVLEFT PREVTOP 52 1) VISIBLEITEMS 3 NONUSABLE
  • link this popuptrigger to its list: POPUPLIST ID 2040 2041
  • add a list like LIST "English" "Spanish" "German" "French" ID 2042 AT (CENTER@120 PREVTOP 52 1) VISIBLEITEMS 2
  • add a REPEATBUTTON "-" ID Form3Minus AT (CENTER@50 PREVBOTTOM+2 AUTO AUTO) that the user will use to decrement a value
  • add a field to hold the value: FIELD ID Form3Count AT (CENTER@80 PREVTOP 24 AUTO) NONEDITABLE UNDERLINED MAXCHARS 4
  • insert a superb image: FORMBITMAP AT (80-(32/2) PREVBOTTOM+2) BITMAP Bitmap
  • in Form4, add a TABLE Table AT (CENTER PREVBOTTOM+4 80 90) ROWS 8 COLUMNS 2 COLUMNWIDTHS 20 60
  • lastly, in Alert1, add a MESSAGE "Nothin' special :)\n"

In forms.c:

  • include the .h
  • in UpdateCount, add this block of code to update and refresh the counter:
    frm = FrmGetActiveForm();
    obj = FrmGetObjectIndex(frm, Form3Count);
    fld = (FieldPtr)FrmGetObjectPtr(FrmGetActiveForm(), obj);
    h = (VoidHand)FldGetTextHandle(fld);
    if( h == NULL )
    {
      h = MemHandleNew (FldGetMaxChars(fld)+10);
      ErrFatalDisplayIf( !h, "No Memory");
    }

    p = (CharPtr) MemHandleLock (h);
    StrIToA(p, cnt);
    MemHandleUnlock (h);

    FldSetTextHandle (fld, (Handle)h);
    FldDrawField(fld);
  • in UpdateTable, add TblSetRowUsable(table, i, true);
  • in PilotMain, handle the "Next" event with this code:
    if (e.data.ctlSelect.controlID == Next)
    {
      if (f < FormLast)
         FrmGotoForm(++f);
    }
  • handle "+" button as follows:
    if (e.data.ctlRepeat.controlID == Form3Plus)
    {
      if (cnt < MAX_COUNT)
         UpdateCount(+1);
    }
  • set active form with a call to FrmSetActiveForm(FrmInitForm(e.data.frmLoad.formID));
  • draw it: FrmDrawForm(pfrm);
  • close the forms when you leave the app: FrmCloseAllForms();
Make the app and test it!

 Solution

Here's the ZIP file.

And here's how the app should like:

Palm Tutorial Palm Tutorial
Palm Tutorial Palm Tutorial

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