Copyright © 2004-2013 - Curt Hill Common Dialogs Easily Obtaining File Names in DevC++ Windows...

Copyright © 2004-2013 - Curt Hill

Common Dialogs

Easily Obtaining File Names in DevC++ Windows Programs

Programs that Use Files• Some programs use exactly the

same file each time– Usually an initialization file in the

same place every time• Most programs can use any file of

the proper format• Typing the file name into a text

box is awkward and error prone• Let Windows show us where it is

with a common dialog boxCopyright © 2004-2013 - Curt Hill

Common File Dialog Box• What is it?

– This is the Windows standard way to select a file name

– There are two flavors: open existing or create new one

• Where: Dialogs tab• There are two of importance today:

– wxOpenFileDialog and wxSaveFileDialog

• Neither will open a file– But they will obtain a file name


What you can do• A common dialog box allows the

user to avoid typing and• Change directory or disk• Choose a file• Change the filter• Accept the chosen file or cancel


Example from PowerPoint


General• Unlike most components they are

non-visual• They can be seen on the form

during design time• Invisible at execution time• They are not seen until executed


DevC++ Design Time


After Drop


Using• Once put on form we still have to

use it• General process is:• Display box• Determine if open or cancel was

done• If Open get the file name • Convert this file to a C style string

pass it to the file


Modal Dialog Boxes• In Windows there are two styles of

dialog box:– Modal– Non-modal

• A non-modal may be displayed, but it does not interfere with the parent window

• A Modal dialog box prevents any input to the parent– It must be dismissed before the parent

is usableCopyright © 2004-2013 - Curt Hill

ShowModal Method• The ShowModal method takes no

parameters and shows the dialog• ShowModal returns an integer that

tells what happened• If this is equal to wxID_OK then the

user approved the file name– Otherwise they cancelled– All file processing should be done only

if a wxID_OK was returned


Design Properties• Message – The contents of the title

bar when Common dialog is displayed

• Name – The name of the component– This will always be referenced from

code• Most other things need to be

referenced using methods


GetPath Method• This is used to obtain the filename

– It also contains the entire directory path– GetFilename only gives the file name

without the path• It returns a wxString• ifstreams and ofstreams need a C

style string• This needs to be converted in order

to pass to a constructor or open method

• How?Copyright © 2004-2013 - Curt Hill

String Conversion• This is relatively easy• Use the wxString method: c_str()

– ifstream inf( OpenDialog1-> GetPath ().c_str());

• You may do in two steps:– wxString name = OpenDialog->GetPath();

– ifstream inf(name.c_str());


Sample Code• Suppose that OpenDial is the object• The following code will open a file: int ret = OpenDialog->ShowModal();if(ret == wxID_OK){

• ifstream inf( OpenDial->GetPath() .c_str()); while(inf) { … } } // end of if


Executed


Filters• By default a common dialog box

will show every file in the current directory– The directory may be changed

• Often we are not interested in every kind of file– A filter allows us to only observe the

files of interest• DevC++ does not allow the filter

to be set at design time– Done with SetWildcard method


Filter Pairs• Each pair consists of two pieces

– A name to be displayed– An expression that describes what to

show• The two are separated by a

vertical bar• The expression may include ? or *

– ? any one character– * any number of any characters


Format• Thus we set:• OpenDialog1->SetWildcard( "Data|*.dat|All|*.* ");

• The odd entries are display• The even entries are the actual filters• See next screen for image


Show Filters


Last Thoughts• There are many other options

– Most of these we do not need• The FileName is persistent• It will show as the last one used in

subsequent executions


Date post:	19-Jan-2018
Category:	Documents
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Copyright © 2004-2013 - Curt Hill Common Dialogs Easily Obtaining File Names in DevC++ Windows...

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