مساعدة بكتابة كود يحسب فاتورة ويظهر بياناتها

In this exercise you will write two applications, CreateTextFile (to save invoice

data) and ReadTextFile (to display invoice data saved in the file).

CreateTextFile displays a frame with four labels and four text fields for

entering invoice data: part number, description, quantity, price per item (grid

layout for this panel is ok). At the bottom of the frame there are three buttons,

"Save To File," "Cancel Item," "Exit." When the first button is clicked, the

values of invoice data are validated, written to file "invoices.txt" and the text

fields are cleared to accept a next set of data. When the second button is

clicked, the text fields are simply cleared. A click on the third button displays a

confirmation dialog that asks the user "Do you really want to exit?" If the user

clicks the No button, the dialog is removed and the user continues entering

invoice data. If the user clicks the Yes button, the application terminates.

When the user clicks the closing icon at the right-top corner of the frame, the

application ends without asking questions.

To support this functionality, CreateTextFile program includes three other

classes GUIframe, SaveHandler, and OutputFile. The frame constructor puts

the labels and text fields for entering invoice data on the top panel, and the

control buttons on the bottom panel. The labels should use a 14 pts bold

Helvetica font. Make sure that the frame cannot be resized, and experiment

with frame dimensions so that it looks nicely. Concentrate everything related

to the GUI appearance in the frame constructor, not in main. Other GUIframe

methods are setUpHandlers, clearTextFields, getTextFields.

Method setUpHandlers creates a SaveHandler object and makes it a listener

to the four text fields and to the Save button. Also, setUpHandlers adds an

anonymous listener to the Cancel button (it calls clearTextFields) and another

anonymous listener to the Exit button (it calls method closeFile of class

OutputFile). Method clearTextFields sets all four text fields to empty strings.

Method getTextFields gets (and trims) the text from four text fields and

combines it into an array of strings for further validation.

Method getTextFields is called from class SaveHandler. If any of the text

fields is empty, SaveHandler shows a message dialog saying "Please enter

data into each field" and returns so that the user can correct error(s). If the

quantity integer is invalid, it shows a message dialog that echoes the user

input and says, e.g., "Illegal integer 1.0. Try again." If quantity is not positive,

in shows a message dialog saying "Integer should be positive. Try again." If

the price per item is invalid, it shows a message dialog that says, e.g., "Illegal

value 25.O. Try again." If the price per item is not positive, SaveHandler

shows a message dialog that says "Value should be positive. Try again."

If user input passes these validation tests, a confirmation dialog displays the

invoice data for inspection and says "Please confirm writing to file." If the user

clicks the Yes button, SaveHandler calls saveToFile (it writes data to file) and

the text fields are cleared. If the answer is No, the user can further edit invoice

values in the text fields. To support these operations, SaveHandler should

receive the GUIframe and OutputFile references in its constructor (it is trivial

for GUIframe; for OutputFile, pass it to the GUIframe constructor and from

that constructor to setUpHandlers and then to SaveHandler).

Class OutputFile has a constructor and methods saveToFile and closeFile.

The constructor creates a Formatter object for the file name passed as an

argument. If the text file cannot be opened, the constructor displays a

message dialog that says, e.g., "Error creating the file invoices.txt" and after

that calls exit to end the program. Method saveToFile calls method format to

save strings (5 and 20 positions) and numeric values (8 and 12 positions) in

the text file. If the operation fails, it shows a message dialog that says "Cannot

write to file" and aborts. Method closeFile shows a confirmation dialog asking

"Do you really want to exit?" If the answer is No, only the dialog is removed

and the user can continue input. If the user clicks the Yes button, the

Formatter is closed and the exit method is called to end the program.

The main method simply creates an OutputFile and passes it to a GUIframe

object.

The second application, ReadTextFile, displays a frame with a text area (with

vertical scrollbars) at the top of the frame and the Exit button at the bottom.

When started, it opens the text file "invoices.txt" (if the operation fails, it shows

a message dialog and calls exit) and displays a header and the file data (one

invoice per line) in the text area.

To support this functionality, ReadTextFile cooperates with classes

GUIframe1 and InputFile. The GUIframe1 constructor puts visual components

on the frame and sets an anonymous listener to the Exit button to call the

closeFile method of class InputFile. Similar to CreateTextFile, make sure that

all visual elements and handled by the GUIframe1 constructor so that main

only creates the frame and the file objects. This application also should not

allow the user to change the size of the frame.

The InputFile constructor opens the text file by creating a Scanner object for

file name passed to is as at argument (make sure you use a proper Scanner

constructor). If this fails, show the message dialog that says, e.g., "Error

creating the file invoices.txt" and abort the program. The InputFile method

readFile adds to the text area the column headers for part number,

description, etc (for output, use a 14 pt bold Monospace font). In a loop,

readFile checks whether the next file record is available, reads four values

from the file (two strings, an integer, and a double) and adds them to the text

area. If anything goes wrong, a message dialog is displayed that says, e.g.,

"File invoices.txt is corrupted", the file is closed and the program ends.

Method closeFile shows a confirmation dialog that asks "Do you really want to

exit?" If the answer is No, the dialog window is simply removed. If the user

clicks on the Yes button, the Scanner is closed and the exit method is called

to terminate the program. The main method simply creates a file and a frame

object and calls readFile.

You see that class GUIframe1 needs to know about InputFile (to call

closeFile), and class InputFile needs to know about GUIframe1 (to write to the

text area). One way to make it happen is to (a) add a method getTextArea to

GUIframe1, (B) pass the InputFile object to the GUIframe1 constructor, and

© pass the GUIframe1 object to method readFile. Another way is to add a

method displayLine to GUIframe1.

Use the same naming, formatting, commenting and coding conventions as

before. Make static, final, local and private everything that can be made static,

final, local or private. Define variables to minimize their visibility. Minimize the

length of code segments in try blocks, include only statements that can throw

an exception. Consult Java documentation (and tutorials) all the time. Test

both applications.

Turn in the source code and the results of execution (crop the windows if you

use the Print Screen command). In the memo, discuss the following issues:

a) Explain how your GUI changes when you change the resolution of your

monitor.

B) Compare data validation techniques for traditional interactive input/output

and for graphical user interface. When is data validation easier to program?

When is it easier to make more complete and effective?

c) Discuss whether anonymous classes are convenient for these programs

and why.

d) Describe techniques that you used for communications between the frame

and file classes for each application.

e) Why do you think that your testing is complete?