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Lecture 3 Programming on Palm OS

Mobile and Handheld Applications 1

Programming of Mobile and Handheld Devices

Lecture 3: Programming for Palm OS

Rob Pooley

[email protected]



Programming conventions

• Each application has a PilotMain() function • Palm OS applications are largely event-driven

and so contain an event loop; – this event loop is only started in response to

the normal launch code. – Your application may

• perform work outside the event loop in response to other launch codes or

• define a different event loop for other codes.



Typical PilotMain

UInt32 PilotMain (UInt16 cmd, void *cmdPBP, UInt16 launchFlags)

{ UInt32 error = StartQuizApp(); if(error) return error; QuizAppEventLoop(); EndQuizApp(); return errNone; }



Simple Start Application

static UInt16 StartQuizApp(void)

{

UInt16 error = 0;

FrmGotoForm(MainForm);

return errNone;

}



Event loop

static void QuizAppEventLoop(void){ Err error; EventType event; do { EvtGetEvent(&event, evtWaitForever); if (! SysHandleEvent(&event)) if (! MenuHandleEvent(0, &event, &error)) if (! AppHandleEvent(&event)) FrmDispatchEvent(&event); } while (event.eType != appStopEvent);



EndQuizApp

static void EndQuizApp(void)

{

FrmCloseAllForms( );

}



Event handlers and related functions

• An application should define and attach event handlers to any resources which require them. In this example there is an event handler for each form which is used.

• When AppHandleEvent is called it can detect events which request the loading of a new form and set the appropriate event handler for that form.

• An event handler is a function which is automatically called, by FrmDispatchEvent, when a particular form is active.

• In this way we set up some of the logic of our application. • In our application there are several types of form, each created

using the Resource Editor tool in the Developer Suite and each with its own buttons.

• We make the Id of each form distinct. It is not strictly necessary for resources of different types to have different Ids.



Typical AppHandleEvent

static Boolean AppHandleEvent(EventPtr event){ UInt16 formId; FormPtr form; if (event->eType == frmLoadEvent) { // Load the form resource. formId = event->data.frmLoad.formID; form = FrmInitForm(formId); ErrFatalDisplayIf(!form, "Can't initialize form"); FrmSetActiveForm(form); switch (formId) { case MainForm: FrmSetEventHandler(form,

MainFormHandleEvent); break; case HistoryForm: FrmSetEventHandler(form,

HistoryFormHandleEvent); break;

case MathsForm: FrmSetEventHandler(form,

MathsFormHandleEvent); break; case WrongForm: FrmSetEventHandler(form,

WrongFormHandleEvent); break; case CorrectForm: FrmSetEventHandler(form,

CorrectFormHandleEvent); break; default: ErrFatalDisplay("Invalid Form Load Event"); break; } return true; } else return false;}



FrmDispatchEvent - pseudocode

Boolean FrmDispatchEvent(EventType *event)

{

Boolean handled = result of calling Form's event handler;

if (handled) return true;

else return FrmHandleEvent(event);

}

• FrmDispatchEvent is written to allow the application to interpret events such as button presses if they are meaningful to this application.

• This is done by calling an event handler which is installed within the current form.

• If that fails, it passes these on to the system’s FrmHandleEvent.



Example of an event handler

Boolean WrongFormHandleEvent(EventPtr event)

{ Boolean handled = false; FormPtr form; switch (event->eType) { case frmOpenEvent:

form = FrmGetActiveForm(); FrmDrawForm(form); handled = true; break;

case ctlSelectEvent:

switch (event->data.ctlSelect.controlID) { case TryAgainButton: FrmGotoForm(MainForm); handled = true; break;

default: ErrFatalDisplay("Mysterious Wrong Form

Button Event"); handled = false; break; }

break;

case frmCloseEvent: MainFormDeinit(FrmGetActiveForm()); handled = false; break;

default: } return handled;}



More on conventions

• Most Palm OS applications contain a user interface made up of forms, which are analogous to windows in a desktop application

• Only one form is normally visible at a time

• The Palm OS approach is to • define the elements of the user interface

separately and • merge these with the application code when

compiling and linking the final application



More conventions

• All applications should use the memory and data management facilities provided by the system.

• Applications employ operating system services by calling Palm OS functions.

• “managers,” are groups of functions that work together to implement a feature usually defined by a type of resource which they “manage”.

• Managers are available, for example, to generate sounds, send alarms, perform network communication, and beam information through an infrared port.



Compatibility with Palm OS

• Integrate with the system software as follows:• Handle sysAppLaunchCmdNormalLaunch• Handle or ignore other application launch codes as

appropriate• In the stop routine, tidy up and return memory

– an application should first flush all active records, then close the application's database, and finally save those aspects of the current state needed for startup.

• Be sure your application uses the system preferences for numeric formats, date, time, and start day of week.

• Don’t obscure shift indicators.



Writing Robust Code

• Check assumptions.• Avoid continual polling.• Avoid reading and writing to NULL (or low

memory). • Check result codes when allocating memory. • Avoid making assumptions about the screen. • Built-in applications can change.



Uniquely Identifying Your Palm OS Application

• Each Palm OS application (in fact each Palm OS database) is uniquely identified by a combination of its name and a four-byte creator ID.

• Each database on the Palm Powered device has a type as well as a creator ID. – The database type allows applications and the OS to

distinguish among multiple databases with the same creator ID.

• Types and creator IDs are case-sensitive and are composed of four ASCII characters in the range 32-126 . – Types and creator IDs consisting of all lowercase

letters are reserved for use by PalmSource, so any type or creator ID that you choose must contain at least one uppercase letter, digit, or symbol



Header files and resources

#include <PalmOS.h>#include "AppDefs.h"

• PalmOS.h is the Palm OS API include file and is always needed. – As a system library header it is enclosed in angle brackets

when it is included.• The other file here is one which you create and place into the src

subdirectory (subfolder) of your project. – It contains all the resource identifiers you will use to link to the

resource definition file and defines a unique symbolic name for each of them.

– I have used the name AppDefs.h for this file, but you can choose your own name.

– As a programmer defined header file, it is enclosed in double quotes when it is included.



The files in a project



AppDefs.h#define MainForm 1000#define MainGotoHistoryFormButton 1000#define MainGotoMathsFormButton 1001#define MainLabel1 1002#define MainLabel2 1003#define MainOKButton 1004#define HistoryForm 1100#define HistoryCorrectButton 1100#define HistoryWrongButton 1101#define HistoryLabel 1102#define HistoryTextField 1103#define MathsForm 1200#define MathsCorrectButton 1200#define MathsWrongButton 1201#define MathsLabel 1202#define MathsTextField 1203#define WrongForm 1400#define TryAgainButton 1402#define CorrectForm 1300#define AcceptCorrectButton 1302



Excerpt from GuessALot.xrd<?xml version="1.0" encoding="UTF-8" standalone="yes"?><PALMOS_RESOURCE_FILE>

<FORM_RESOURCE RESOURCE_ID="1000"><COMMENT_TEXT> "Welcome to Guess a Lot." </COMMENT_TEXT><FORM_ID> 1000 </FORM_ID><BOUNDS>

<LEFT> 2 </LEFT><TOP> 2 </TOP><WIDTH> 156 </WIDTH><HEIGHT> 156 </HEIGHT>

</BOUNDS><USABLE> TRUE </USABLE><MODAL> TRUE </MODAL><SAVE_BEHIND> TRUE </SAVE_BEHIND><HELP_ID> 0 </HELP_ID><MENU_ID> 0 </MENU_ID><DEFAULT_BUTTON> 0 </DEFAULT_BUTTON><FORM_OBJECTS>

<FORM_TITLE><TEXT> "Guess a Lot" </TEXT>

</FORM_TITLE><FORM_BUTTON>

<ID> 1000 </ID><BOUNDS>

<LEFT> 93 </LEFT><TOP> 97 </TOP><WIDTH> 58 </WIDTH><HEIGHT> 12 </HEIGHT>

</BOUNDS><USABLE> TRUE </USABLE><ENABLED> TRUE </ENABLED><TEXT> "History" </TEXT><LEFT_ANCHOR> FALSE </LEFT_ANCHOR><FONT_ID> STD_FONT </FONT_ID><BUTTON_FRAME> STANDARD_BUTTON_FRAME </BUTTON_FRAME>

</FORM_BUTTON>



Palm OS makefile ## -----------------------------------------------------------------------# Palm OS Generic Makefile for Eclipse v1.0.0# PalmOS4/68K## Fill in this file to specify your project and the source that you want# to build, and the settings involved in the build. The makefile-engine.mk# will then do the hard work of the makefile and dependency handling.## After starting a new project, please remember the following steps...# 1. Add all sources and resources in SOURCES and RESOURCES# 2. Review the other settings as needed.### -----------------------------------------------------------------------SHELL = /bin/sh## -----------------------------------------------------------------------# Set up the artifact name, which is the root name of your project's output# without the extension.## The PRC and/or static library name, the database name, and other file names # are based on the artifact name## -----------------------------------------------------------------------ARTIFACT_NAME =GuessaLotMoreEMPTY =SPACE =$(EMPTY) $(EMPTY)ESCAPED_ARTIFACT_NAME = $(subst $(SPACE),\ ,$(ARTIFACT_NAME))PRC_NAME = $(ESCAPED_ARTIFACT_NAME).prcLIB_NAME = $(ESCAPED_ARTIFACT_NAME).a## -----------------------------------------------------------------------# Sources and Resources# List all the sources (.c/.cpp) and resources (.xrd) in your project# Use project relative path names with forward slashes (src/code.cpp).# Please do not use spaces in directory names.# A note about XRD resource files: If you have existing .rsrc or .rcp files, # refer to the documentation for the GenerateXRD tool to convert them into # XRD files for use with all Palm OS SDKs.## -----------------------------------------------------------------------# TODO: Update all sources and resourcesSOURCES = src/AppMain.cRESOURCES = rsc/GuessaLot.xrdSLIB_DEF_FILE =



Palm UI and other Resources

• Palm OS applications are built using two main input files and a software development environment which combines and links the outputs from these.– See

www.palmos.com/dev/support/docs/dev_suite/PalmOSDevSuite/Tools_Overview.html

• We have seen the first of these input files – the source code, written in C or C++.

• The second defines the structures available in the application, such as GUI screens and buttons. It is written as an XRD resource file, which is structured as an XML file.



Process for Building Palm OS 68K Applications

PalmOS.h AppResources.h

C source file

Application

Resource description file

app.xrd



Building Palm OS 68K applications

• Palm OS Developer Suite includes PRC-Tools. • PRC-Tools includes patched versions of the GNU packages

gcc, binutils, gdb, and various post-linker tools. • Create a 68K C/C++ Project for your source code.

• You can choose either a standard make project or a managed make project.

• Create your C/C++ source files using the C/C++ editor provided.

• Create your application's XML resource definition (XRD) files either by using Palm OS Resource Editor or by editing the XML file using a text editor.

• Build your project. • From Developer Suite, select Build Project or Rebuild

Project to build your 68K application.



Testing and running

• Test your application by running it on Palm OS Emulator, Palm OS Simulator, or a Palm Powered™ device.

• From Palm OS Developer Suite, select Run > Run to open the Run dialog box, and

• use the Target tab to select the run target for your application.

• Debug your application, using the debugger integrated with Palm OS Developer Suite.

• From Palm OS Developer Suite, select Run > Debug to open the Debug dialog box, and

• use the Target tab to select the debug target for your application.



Creating resource (XRD) files

• The following sequence takes you through the steps required to create the XRD file

• It starts from the Palm OS project environment• It creates a new XRD file using the Palm OS

graphical resource builder• Remember that this does not create the

corresponding C header file automatically• You have to edit a suitable .h file with the correct

#define directives



Opening the resource editor









Select new resource from the edit menu







