Delphi Mobile Point of Sale Software - Felix John COLIBRI. Using FireBase, FireDac, DataSnap, Rest, Wifi, and FireMonkey

• abstract : Android tablet or smartphone point of sale application using a WIFI connection to a DataSnap REST Server connected with FireDac to a FireBird database
  
• key words : Android, WIFI, point of sale device, REST Client, REST Server, JSON, DataSnap methods, FireDac, FireBird
  
• software used : Windows XP Home, Delphi XE7, Android 4.3
  
• hardware used : Pentium 2.800Mhz, 512 M memory, 140 G hard disc, Samsung Galaxy Nexus, Android 4.3
  
• scope : Delphi Xe6 to Xe8, Delphi Seattle, Delphi Berlin
  
• level : Delphi developer
  
• plan :
  
  • WIFI Point of Sale devices
    
  • The Rest Server
    
  • The Desktop VCL Rest Client
    
  • The Mobile Rest Client
    
  • Download the Sources
    

1 - WIFI Point of Sale devices

Wifi is quite adapted to solve this kind of problem.

From a Delphi point of view, this can be implemented using

• Firemonkey for the Client mobile device (smartphone, tablet, dedicated mobile device)
  
• REST services for communications between the client and the server
  
• to offer those services from the server, FireBase as a database, FireDac for data access, DataSnap as a REST server and Json for packet formatting
  

In this article we will present the structure of such a REST Server / REST clients architecture :

• the Rest Server
  
• a Rest Client on a PC using the VCL
  
• a Rest Client using FireMonkey for the shop workers
  

2 - The Rest Server

2.1 - The choice of the components

To communicate with the Clients, the Server can use any transfer protocol. However this protocol must be compatible with the mobile devices, and, in this case, Rest is a good solution.

To implement Rest services, a Tcp Server could be used. We would have to handle the marshalling / unmarshalling of the objects ourselves. Here comes JSon, which was just created for this very purpose: transfer objets from one place to the other.

And for JSon, FireDac offers an out of the box library.

Finally the Client must be able to request the data. If the data is in the form of objects, DataSnap with methods (function returning objects in our case) can be used.

2.2 - Building the DataSnap Rest Server

	start delphi
	select "Tools | Options" and in "Default Project:", fill the project folder name and click "Ok"

	select "File | New Other"
	Delphi displays all the projects available
	select "DataSnap Server"
	all available servers are displayed
	select "DataSnap Rest Application" and click "Ok"
	Delphi asks what kind of WebBroker Application we want to create
	we prefer to use the Indy Tcp Server. So select "Stand Alone" and click "Next"
	Delphi ask us if we want "Vcl" or "FireMonkey"
	for the Rest Server, keep "Vcl" selected and click "Next"
	Delphi asks about the Port of this Web Server
	when clicking "test port", in our case 8080 was used. So we selected 8081 and click "test port" again:
	the port can be used
	click "Ok" and "Next"
	Delphi asks us which features we want
	in our case, no authentication, and we keep, for this tutorial, the sample DataSnap method (a "reverse string" method). So keep the defaults and click "Next"
	Delphi can add a tDataModule
	select "tDataModule" and click "Next"
	Delphi proposes the project folder
	navigate to your projects folder and click "Finish"
	Delphi builds the necessary files and presents the Server Form

2.3 - The WebBroker Rest Server Units

	click "Save Project"
	save "FormUnit1.Pas" as "u_server_main.pas". This is the tForm that will be displayed on the desktop, allowing the user to start and stop the server
	save "WebModuleUnit1.pas" as "u_web_module.pas"
	save "ServerMethodsUnit1.pas" as "u_server_methods.pas"
	save "Project1.dproj" as "p_12_rest_server.dproj"

• u_server_main.pas will start / stop the server, and can be used to launch a web browser for test purposes
  
  
• u_web_module.pas contains all the components which manage the Rest Server. It contains the basic DataSnap Server components, plus the components used by the Rest type of Server
  
  
• u_server_methods.pas is a tDataModule containing all the methods the Rest Server will offer to its clients. In Our case, the Wizard has prepared two functions, EchoString and ReverseString.

  Unit u_server_methods;   Interface     Uses System.SysUtils, System.Classes, System.Json,         Datasnap.DSServer, Datasnap.DSAuth,         DataSnap.DSProviderDataModuleAdapter;     Type       {$METHODINFO ON}       TServerMethods1 =           Class(TDataModule)             Private             Public               Function EchoString(Value: string): string;             End;       {$METHODINFO OFF}   Implementation     {$R *.dfm}     Uses System.StrUtils;     Function TServerMethods1.EchoString(Value: string): string;       Begin         Result := Value;       End; // EchoString     End.

  Notice

  • the tDataModule ancestor
    
  • the $METHODINFO compiler directive which enables the Server to call our methods
    

So

change all ServerMethodsUnit1 identifiers into u_server_methods (3 occurences)

Eventually unblock the Windows lock :

2.4 - Test the Rest Server

To test "reverse string"

	run the project
	the server form is displayed
	click "Start"
	the Tcp Server is started ("start" and the port are grayed)
	click "Open Browser"
	the default browser is opened with the   http://localhost:8081/ URL
	clicking on "Reverse String" calls the WebBroker default action and reverses the string
	to see the other available functions, click the "Server Functions" hyper link
	two groups of methods are displayed; Admin and ServerMethods
	click ON THE PLUS before "TServerMethods" (yes, it is a pale gray on a pale blue plus button)
	all the available methods are displayed
	to test the "ReverseString" method, click the "+" before "ReverseString" (just as difficult to see as the other "+" on this form)
	an edit for typing the parameter of the function are presented
	type a string, say abcd
	the result of the method are presented

Note

• it would have been hard to better hide the test functions then they did. We did not see the "+" sign, until we read about them in the doc
  
• to stop the server, you cannot use "Ctrl F2". Use the "Stop" button and then close the Server form
  
• the test .HTML pages have been generated by the two tPageProducers which are on the tWebModule.

  

  Those .HTML page also use all the css\, images\ js\ and templates\ displayed in the project manager. Those files would not be necessary for a simple REST server.
  

2.5 - The DataSet transfer Rest method

We chose the Delphi "MastApp" database, and will use

• the CUSTOMER table
  
• the ORDERS table (with a CUSTNO foreign key)
  
• the ITEMS table (with an ORDERNO foreign key)
  

If you select another database, just find 2 or 3 tables with a master / detail relationship. We added the Sql Scripts to allow you to create and fill those tables.

Copy the database near the Server:

	create a _data\ folder
	copy the MASTAPP_25.FDB base there

We will start with a client which will display the CUSTOMER ( CUSTNO, COMPANY ) table.

2.6 - The Firedac components

First we initialize the link to the FireBird driver :

	select the u_server_methods unit
	from the Tool Palette, drop a tFDGUIxWaitCursort on the DataModule
	then drop a tFDPhysIBDriverLink
	double click on the DataModule to create its OnCreate method and initialize the driver's DriverId, VendorHome and VendorLib Properties by code : Procedure TServerMethods1.DataModuleCreate(Sender: TObject);   Begin     With FDPhysIBDriverLink1 Do     Begin       DriverId:= 'FB25';       VendorHome := 'C:\Program Files\Firebird\Firebird_2_5';       VendorLib := 'fbclient.dll';     End; // with ADPhysIBDriverLink1   End; // DataModuleCreate

Please note:

• we hard coded the location of our FireBird 2.5 fbclient.dll location
  
• if you use another version of Firebird, or Firebird was installed in another folder, adjust the code accordingly
  
• we also assume a 32 bit PC. If you use a 64 bit PC, you should change the Firebird Client .DLL also
  
• you could also initialize the FireDac driver using the FdDrivers.Ini file. This has been explained in great detail in the following Delphi FireDac Connection article
  
• of course, if you use another database engine, you should use the matching initialization code
  

drop a tFdConnection on the DataModule

in the DataModuleCreate event, add this code which essential fills the tFdConnection Params property: Procedure TServerMethods1.DataModuleCreate(Sender: TObject)                                      ; //   Begin     // o o o     With FdConnection1 Do     Begin       Close;       With Params Do       Begin         Add('DriverID=IB');         Add('Server=localhost');         Add('Database= C:\prog\delphi_6\2014_xe7\13_mobile_pos\_data\Mastapp_25.fdb');         Add('User_Name=SYSDBA');         Add('Password=masterkey');       End; // with Params do       LoginPrompt:= False;       Open;     End; // with FdConnection1   End; // DataModuleCreate

• the connection cannot be tested, but we will create a Server Method to test it
  

drop a tFdQuery on the DataModule, rename it fd_customer_query, and in it's Sql property type   SELECT custno, company   FROM customer

2.7 - Test of the Database Connection

	in the u_server_methods unit, in the tServerMethods Class add the following definition: Function f_test_connection: string;
	type Shift Ctrl C to create the implementation and fill the body: Function TServerMethods1.f_test_connection: string;   Begin     FDConnection1.Open;     If FDConnection1.Connected       Then Begin           Result:= 'connected';           FdQuery1.Open;           If FDQuery1.Active             Then Result:= Result+ ' fdQuery Open'             Else Result:= Result+ ' *** fdQuery Closed';         End       Else Result:= '*** connection pb';   End;
	run, start the server, open the browser, click on the function invoker link, open the TServerMethod, click on the "+" before f_test_connection, click "EXECUTE"
	the database is connected and the query opened:

2.8 - The Server Method returning a tDataSet

To marshall (send over as a stream) the dataset, we will use the Json formatting. Our CUSTOMER ( CUST_NO, COMPANY ) table will be formatted as :

For the illustration, we indented the JSON text, but usually it does not contain spaces (the punctuation is enough to parse the format)  :

This dataset formatting will be performed by FireDac components :

	select the u_web_module
	from the Tool Palette select a tTFDStanStorageBin and drop it on the module select a tFDStanStorageJSON and drop it on the module

Now we will add the DataSnap Method:

	select the u_server_methods datamodule
	in the tTServerMethods1 Class, add this function : Function f_c_get_customer_name_list: TFDJSONDataSets;
	since the tFDJSONDataSets is unknown (the red wriggles), add the Data.FireDACJSONReflect to the Interface Uses clause:
	with the cursor between Class and End, press Shif Ctrl Click to create the function body, and type this code: Function TServerMethods1.f_c_get_customer_name_list: TFDJSONDataSets;   Begin     // -- Clear active so that query will reexecute.     fd_customer_query.Active := False;     Result := TFDJSONDataSets.Create;     // -- convert the Query Answer Set into a JSON DataSet     TFDJSONDataSetsWriter.ListAdd(Result, fd_customer_query);   End; // f_c_get_customer_name_list

To explain the function content :

• FireDac has a tFDJSONDataSetsWriter Class with a ListAdd Class function.
  
• we can add one or several queries to this Class
  
• when requested, the writer will convert the queries Answer Sets into the tFDJSONDataSet using RTTI (Reflection, in Java parlance).
  

2.9 - Keep the Server running

3 - The Desktop VCL Rest Client

3.1 - The first Client

To build the client

	launch Delphi, and select "File | New | Vcl Application"
	a standard VCL application is created
	save the project and unit in a Client_VCL\ folder under u_client_vcl and p_13_rest_vcl_client
	run the project to make sure everything is ok

3.2 - The Client Rest import unit

	make sure the Rest Server is running. The server will be called by the Delphi IDE to import the classes and method definitions
	add the import units by selecting "File | New | Other | DataSnap Server"
	the Rest components are displayed. Since we are not creating a DataSnap server (we started a standard VCL project), the dialog now presents the DataSnap client units:
	select the "DataSnap Rest Client Module" and click "Ok"
	the wizard asks to select the local or remote server
	for this VCL client located on the same PC, we keep the "Local Server" and click "Next"
	the wizard asks what kind of server to use
	we keep the "DataSnap Stand Alone Server" and click "Next"
	the wizard asks what the connection parameters are :
	we change the port to 8081 and click "test"
	the parameters are correct
	we click "Ok" and "Finish"
	the wizard has created the two import units.

• the ClientClassesUnit1 which generates the DataSnap methods proxies
  
• the ClientModuleUnit1 tDataModule with a TDSRestConnection component which will be uses as a TCP client
  

	change ClientClassesUnit1 into u_client_classes
	add Data.FireDACJSONReflect to the Interface Uses clause
	change ClientModuleUnit1 into u_client_datamodule. In this Unit, replace ClientClassesUnit1 with u_client_classes
	Run the client and close it

	select the u_client_datamodule form
	from the Tool Palette select a tTFDStanStorageBin and drop it on the module select a tFDStanStorageJSON and drop it on the module

3.3 - Fetch the Customer from the Client

• add a tDataSet to the client Form. In this case a memory dataset, since the content will be provided by the Rest Server
  
• call the f_c_get_customer_name_list Function to fill the dataset.
  

	select the u_client_form
	from the Tool Palette, select a tFdMemTable, drop it on the form and rename it fd_customer_list_dataset

	add the u_server_methods to the Implementation Uses clause
	also add the Data.FireDACJSONReflect which contains the TFDJSONDataSets Class
	in the Private section of tForm1 Class, add this Procedure declaration  : Procedure get_customer_name_list;
	create the body (Shift Ctrl C) and type its content: Procedure TForm1.get_customer_name_list;   Var l_c_json_dataset_list: TFDJSONDataSets;   Begin     // -- clear the dataset     fd_customer_list_dataset.Close;     // -- fetch the dataset list from the Rest Server     l_c_json_dataset_list := ClientModule1.ServerMethods1Client.f_c_get_customer_name_list;     // -- read the first dataset of this list into the memory dataset     fd_customer_list_dataset.AppendData(       TFDJSONDataSetsReader.GetListValue(l_c_json_dataset_list, 0));     // -- opent the customer_list dataset     fd_customer_list_dataset.Open;   End; // get_customer_name_list
	compile the project (or

	from the Tool PalEtte drop a tDataSource component and set its DataSet to fd_customer_list_dataset drop a tDbGrid component and set its DataSource property to DataSource1
	drop a tButton, fetch the data and display it in the grid : Procedure TForm1.display_customer_list_Click(Sender: TObject);   Begin     get_customer_name_list;   End; // display_customer_list_Click
	run the Client and click display_customer_list_
	here is the glorious result :

4 - The Mobile Rest Client

4.1 - The SmartPhone DataSnap Rest Client

We will demonstrate the case with an Android Smartphone (Samsung Nexus), but any other Android phone or tablet, or Apple iPhone or tablet would work, thanks to the "single code base" Delphi principle.

4.2 - The Mobile check

However just a couple of reminders

• check your Java pathes. We installed Delphi Xe7 asking to install the Java files. So they were all downloaded and copied into
  • Program Files\ for the Java SDK
    
  • C:\Documents and Settings\All Users\Documents\Embarcadero\Studio\15.0\PlatformSDKs
    for the Android SDK and NDK
    
  You can check that Delphi can use those files with "Tools | Options | Environment Options | SDK Manager", where no combo should display a yellow triangle warning
  
• to deploy the Delphi build ARM code, the smartphone must be linked to the PC using an USB cable. When this cable is plugged into the PC, the phone asks whether you want to use USB debugging, which you should accept
  

4.3 - Testing the Android WIFI and connection

4.3.1 - WIFI connection

Before diving into the FireMonkey code, it is important to test the connection.

Our REST Server and REST client behave in a classical Client / Server mode:

• the Server is started at some known IP, Port
  
• the Client connects to this fixed IP, Port, and sends some request
  
• the Server sends some answer back
  

4.3.2 - Assigning a Fixed IP to the Server

Our server is located on a PC linked to a switch. This switch has a manager which

• displays the WIFI password
  
• contains a DHCP server which allocates the devices IP.
  

So we froze the Server IP, setting its value to 198.168.1.14.

We can check this using IPCONFIG :

The Port of our REST Server application was set when we created this Server with Delphi. It is 8081.

4.3.3 - Adding the Android device to the network

• the switch WIFI manager has a dialog displaying its WIFI parameters. In our case
  • security WPA etc
    
  • password : some value, in our case a 26 byte Hex number, like 439F5 etc
    
• we typed this password on the Android device, by selecting "settings | WIFI", in the WIFI servers in the area, selecting our WIFI network, and then entering the WIFI password
  

4.3.4 - Testing the Android connection

• the Switch displays the IP of all WIFI connected devices. In our case the dynamically assigned IP was 192.168.1.20
  
• we can also display the WIFI information including the device's IP on the smartphone itself. Those WIFI settings can be tested by a Delphi application using JNI (Java Native Interface) Classes. This not obvious, but Stack Overflow and Google allowed us to find the solution. Here is our Delphi Android app displaying the Android IP:

  
  

4.3.5 - Testing the TCP Connection

This test was performed using a tIdTcpClient which tries to Connect.

We used a small FireMonkey project with a tIdTcpClient, 2 edits, a button and a memo. Here is the main FireMonkey form code :

And here is the successful result :

4.4 - The FireMonkey DataSnap REST Client

4.4.1 - The steps

• run the server
  
• create the FireMonkey application
  
• add the DataSnap method import units
  
• write the user code
  

The FireMonkey client application steps are quite similar to the VCL client applications steps, with a couple of differences

• we must assign the Server IP
  
• to display the data, we cannot use a tDbGrid which is Windows VCL specific, but will use FireMonkey controls
  

4.4.2 - The FireMonkey application

	start Delphi
	select "File | New | Multi Device Application"
	the FireUi multi device dialog is presented
	select "Blank Application" and click "Ok"
	the Windows Master page of the multi designer is displayed (both left and right panel have been shrinked to display the central Master / View part)
	select the "Views" combo, display the available formats, and select "
	all available form factors are presented
	select the "Android 4" form factor (or whatever view matching your Android device)
	the phone look is displayed :
	select "File | Save Project As", create a folder client_Firemonkey\  and type u_android_client zz_pos_client We use the "zz_" prefix for our Delphi Android projects to display them at the end of the Android Application pages

	connect the USB cable of your android device to the Delphi PC
	the android device asks you to confirm the debug mode : "Allow Usb Debugging ?"
	touch "ok"
	the status line displays the debugging icon
	brushing the finger down on the status line confirms this debugging mode :
	and the phone is displayed in the windows explorer Delphi can now deploy any FireMonkey to the Android device

	drop a Button on the Form
	select the Android platform. In the project
	run the application (F9)
	the compiler will display "compiling, linking, deploying, stripping symbols, packaging, installing" If the device is active, you will see our page with Button1. If the phone is in sleep mode, pushing "Power" will display the same thing. and the application is at the end of the application pages:

4.4.3 - The REST Client application

	make sure the Rest Server is running. The server will be called by the Delphi IDE to import the classes and method definitions
	add the import units by selecting "File | New | Other | DataSnap Server"
	the Rest components are displayed. Since we are not creating a DataSnap server (we started a standard VCL project), the dialog now presents the DataSnap client units:
	select the "DataSnap Rest Client Module" and click "Ok"
	the wizard asks to select the local or remote server
	for this FireMonkey client connected by WIFI, select the "Remote Server" and click "Next"
	the wizard asks what kind of server to use
	we keep the "DataSnap Stand Alone Server" and click "Next"
	the wizard asks what the connection parameters are :
	we type the 192.168.1.14 IP and change the port to 8081. Then click "test"
	the parameters are correct
	we click "Ok" and "Finish"
	the wizard has created the two import units.

	change ClientClassesUnit1 into u_client_classes
	add Data.FireDACJSONReflect to the Interface Uses clause
	change ClientModuleUnit1 into u_client_datamodule. In this Unit, replace ClientClassesUnit1 with u_client_classes
	compile the client by typing Shift F9 (or "Project | Build")

• the Android cross-compilation and Android deployment is rather lengthy. This is the reason we used "Build" rather than "Run"
  
• even then, the compiling is still longer then the Windows compilation. It is possible to return to the Windows target platform until the project is complete, and then shift back to the Android target platform
  
• as far as the import units are concerned, we could have copied the VCL DataSnap import unit, and changed the DsRestConnection1 host address. We can even test the connection by double clicking on this component :

  
  

4.4.4 - Add the FireDac JSON components

	select the u_client_datamodule form
	from the Tool Palette select a tTFDStanStorageBin and drop it on the module select a tFDStanStorageJSON and drop it on the module

4.5 - Fetch the Customer from the Client

	select the u_android_client_form
	from the Tool Palette, select a tFdMemTable, drop it on the form and rename it fd_customer_list_dataset

	drop a tMemo on the tForm
	write the display global Procedure which simply adds the text to the Form's Memo1 : Procedure display(p_text: String);   Begin     Form1.Memo1.Lines.Add(p_text);   End; // display

	add the u_server_methods to the Implementation Uses clause
	also add the Data.FireDACJSONReflect which contains the TFDJSONDataSets Class
	in the Private section of tForm1 Class, add this Procedure  : Procedure get_customer_name_list;
	create the body (Shift Ctrl C) and type its content: Procedure TForm1.get_customer_name_list;   Var l_c_json_dataset_list: TFDJSONDataSets;   Begin     // -- clear the dataset     fd_customer_list_dataset.Close;     // -- fetch the dataset list from the Rest Server     l_c_json_dataset_list := ClientModule1.ServerMethods1Client.f_c_get_customer_name_list;     // -- read the first dataset of this list into the memory dataset     fd_customer_list_dataset.AppendData(       TFDJSONDataSetsReader.GetListValue(l_c_json_dataset_list, 0));     // -- opent the customer_list dataset     fd_customer_list_dataset.Open;   End; // get_customer_name_list Both the definition and the body can be copied from the VCL u_client_form Unit
	drop a tButton and write the code which fetches the data and displays it in the tMemo : Procedure TForm1.display_customer_list_Click(Sender: TObject);   Begin     get_customer_name_list;     With fd_customer_list_dataset Do       While Not Eof Do       Begin         display(Format('%6s %s',             [ Fields[0].AsString, Fields[1].AsString ] ));         Next;       End; // while not Eof   End; // display_customer_list_Click
	for the first test, change the platform target to "Windows" ("Project Manager | zz_pos_project | Target Platform"
	run the VCL project
	this is the output :

4.6 - Bind the DataSet to Visual Controls

For production applications, we will use FireMonkey controls, and bind them visually to the tFdMemDataSet.

To bind the tFdMemDataSet fields to the columns of the tListView, we must create dataset fields. Creating tFields is difficult at design time, but creating FieldDefs is possible

To create the tFieldDefs

	select the tFdMemDataSet
	in the Object Inspector, select the FieldDefs property and click on the Ellipsis ( ... )
	this is a standard sub-item editor
	add a tFieldDefs by clicking on the top-left yellow icon "Add New"
	a new tFieldDef has been created and is displayed in the Object Inspector
	change the Name property into CUSTNO
	do the same for the second tFieldDef, with name COMPANY
	here is the result :

Now add a tListView and bind it :

	drop a tListView on the form
	select the "Detail" listview, by selecting in the Object Inspector "Listview | ItemAppearance | ListItemRightDetail" The listview will display a .INI kind of two "key-value" columns list
	open the LiveBindings Designer by selecting "View | LiveBindings Designer" (or by selecting the ListView1, selecting it's LiveBindings
	the LiveBindings Designer is opened, displaying all the bindable objects
	bind "Listview Item.Text" to "MemDataSet CUSTNO" (drag the mouse from the Item.Text to the CUSTNO
	bind the Item.Detail to the COMPANY
	this is the current situation :
	run the (VCL) project and click on the Button
	opening the DataSet automatically displays the values in the ListView :

Please note

• in our Delphi XE7 version, the LiveBindings Designer would not display the tFdMemDataSet fieldefs we just created. Closing the app and reloading it did the trick.
  

4.7 - Run on the Android Mobile Device

Therefore

	change the Designer view back to "Android 4 inches"
	change the Target Platform to "Android"
	run the application
	this is the result

Please note

• in our case, the "Run" took between 2 and 3 minutes. This is the reason why we preferred to first run in Windows mode
  
• let's stress again that it is the "single code base" which allowed us to code in Windows Mode and then run in Android mode
  • we also encountered a "F2039" error, because we added an incorrect second "]" in the Format of the fields
    
  • our display is quite primitive, to say the least. For customer applications, we would resize the controls, add shading, more sophisticated controls etc.
    

5 - Remarks

"File | New | Multi Device Application" automatically calls the multi device designer. This wizard works with a "Master View" which contains the common elements of the design, and one or several device specific views. This explains why

• properties like the Name of controls are in the Master View, and to change a Name, we must switch to the Master View
  
• if we move the controls in the Master View, the changes are not propagated to the other Views. Each view manages the graphic properties. Those properties are saved in a separate .DFM, named called in our case "u_android_client_form.NmXhdpiPh.fmx".

  This .DFM obviously contains the delta values :

  Inherited Form1_NmXhdpiPh: TForm1_NmXhdpiPh   ClientHeight = 615   ClientWidth = 400   DesignerMasterStyle = 0   Inherited display_customer_list_: TButton     Size.Width = 225.000000000000000000   End   Inherited customer_memo_: TMemo     Size.Width = 385.000000000000000000     Size.Height = 73.000000000000000000   End   Inherited ListView1: TListView     Size.Width = 385.000000000000000000     Size.Height = 457.000000000000000000   End   Inherited fd_customer_list_dataset: TFDMemTable     Left = 264   End   Inherited BindSourceDB1: TBindSourceDB     Left = 136     Top = 64   End   Inherited BindingsList1: TBindingsList     Left = 36     Top = 61   End End

• we think that this multi-device designer is a good tool for similar size devices, but for building applications targeted to phones, tablets and desktop devices, the design will have to be separated

• for our first Android trials we used the Windows Target Platform because of round trip speed. Of course the resulting FireMonkey Windows layout is not adapted. The goal was NOT to build a desktop application. When the code was working as expected, we switched to the Android Platform.

  This also demonstrate that the Design Views and the Target Platform are two separate concerns. In the end, however, we selected at the same time an Android view and an Android target platform
  

5.1 - What's Next ?

There are many possible extensions and improvements :

• add an "update" function. The user can enter data which is then sent back to the Server
  
• operate on many table : our single table example is quite simplistic. At least we should be able to use Master / Detail relationships
  
• in a multi user environment, we should take care of the threads
  
• finally a Business Object organization can simplify the Business Rules handling.
  

5.2 - What kind of devices / applications

And different devices can be used for different kind of applications

• phones for simple requests / entries with simple screens
  
• tablets for more elaborate reports, computations, advertising or guides
  
• desktop devices for application with richer screen designs : cash register, accounting etc
  

5.3 - The Datasnap Wizards

5.4 - Proxy Generation

• the DataSnap framework generates the units containing the proxies
  
• at run time, the Client works with the proxy, and the REST Client communicates with the REST Server to get information or other objects from the Server.
  
• the code of the proxy was completely handled by the DataSnap framework. All we had to do was call the method to retrieve and instantiate the client proxy.
  

5.5 - The article title

5.6 - References

• the Delphi WIKI contains several tutorials and demos about REST services
  
• Pawel GLOWACKI wrote a series of 11 Delphi Labs: DataSnap code samples, ranging form a simple calculator to authentication and callbacks
  

• we used Jim MCKEETH screen grabber Android Screen View.
  As explained in the "readme", it simply uses the ADB (Android Debug Bridge) to fetch the screen image and display in the grabber's Form.
  

• those tests involve JNI (Java Native Interface). We used two sources
  
  • Brian LONG was the first to post about the topic
    
  • Matthew MEAD posted 3 articles about Using the Java Native Interface with Delphi
    
• Remy LEBEAU wrote about Delphi XE6 and Android Ping
  Whenever we had any Tcp / Ip problem, this is the man who always provided, in Embarcadero's forums or StackOverflow, an answer, usually with a piece of code which solved the problem.
  
• also many thanks to Alexis FRUHINSHOLZ, co founder of SocialCompare, who helped us with the WIFI connection diagnostic tools
  

6 - Download the Sources

• delphi_point_of_sale_software.zip the delphi project group containing the Server, the VCL Client and the Android FireMonkey Client (268K)
  
• firebird_mastap_database_sql_script.zip the Sql Script to rebuild the Mastapp database (6 K)
  
• mastapp_firebird_25.zip the binary of the MastApp demo database, in FireBird 2.5 (88 K)
  

The .ZIP file(s) contain:

• the main program (.DPR, .DOF, .RES), the main form (.PAS, .DFM), and any other auxiliary form
  
• any .TXT for parameters, samples, test data
  
• all units (.PAS) for units
  

• are self-contained: you will not need any other product (unless expressly mentioned).
  
• for Delphi 6 projects, can be used from any folder (the pathes are RELATIVE)
  
• will not modify your PC in any way beyond the path where you placed the .ZIP (no registry changes, no path creation etc).
  

• create or select any folder of your choice
  
• unzip the downloaded file
  
• using Delphi, compile and execute
  

The Pascal code uses the Alsacian notation, which prefixes identifier by program area: K_onstant, T_ype, G_lobal, L_ocal, P_arametre, F_unction, C_lasse etc. This notation is presented in the Alsacian Notation paper.

As usual:

• please tell us at fcolibri@felix-colibri.com if you found some errors, mistakes, bugs, broken links or had some problem downloading the file. Resulting corrections will be helpful for other readers
  
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7 - The author