.NET/ASP.NET/C#/VB.NET PDF Document SDK

Qt has widgets for lists, tables, and trees. This chapter is limited to the list widget because Qt has a very powerful approach to lists, tables, and trees using models and views (covered in detail in 5). The list widget is used to present a list of items to the user. You can add widgets to the list using the addItem(const QString&) or addItems(const QStringList&) methods. When the user changes the current item, you can tell by connecting to the currentItemChanged (QListWidgetItem *, QListWidgetItem *) or currentTextChanged(const QString&) signals. Notice that the current item does not always have to be selected it depends on the selection mode. With the selectionMode property, you can enable the user to select only one item, a contiguous range of items, or all items. Whenever the selection is changed, the itemSelectionChanged signal is emitted. The items of the list view can be added to the list from text strings, but they are stored as QListWidgetItem objects. These objects are owned by the list widget and automatically deleted when the list widget is destructed. If you want to remove an item from a list, simply find it by using the currentItem property or the item(int row) method; then delete it.

barcode font excel 2013 free, barcode generator excel 2007 free, print barcode labels in excel 2010, excel barcode add in, barcode activex control for excel 2010 free download, free barcode addin for excel 2007, microsoft excel 2013 barcode font, barcode add in for excel 2013, how to make barcode in excel 2003, random barcode generator excel,

To recap what we ve explored so far, we ve seen how to work with variables to hold information, how to write expressions that perform calculations, how to use selection statements that decide what to do, and how to build iteration statements that can do things repeatedly. There s one more basic C# programming feature we need to look at to cover the most important everyday coding features: methods.

You associate this CheckBox with an Atlas Select control like this: var g_sel = new Sys.UI.Select($('Select1')); The Select control exposes the methods described in Table 4-25. Table 4-25. Select Control Methods

As we saw earlier, a method is a named block of code. We wrote a method already the Main method that runs when our program starts. And we used methods provided by the .NET Framework class library, such as Console.WriteLine and File.ReadAll Lines. But we haven t looked at how and why you would introduce new methods other than Main into your own code. Methods are an essential mechanism for reducing your code s complexity and enhancing its readability. By putting a section of code into its own method with a carefully chosen name that describes what the method does, you can make it much easier for someone looking at the code to work out what your program is meant to do. Also, methods can help avoid repetition if you need to do similar work in multiple places, a method can help you reuse code. In our race car example, there s a job we may need to do multiple times: reading in numeric values from a file. We did this for timing information, but we re going to need to do the same with fuel consumption and distance. Rather than writing three almost identical bits of code, we can put the majority of the code into a single method. The first thing we need to do is declare the method we need to pick a name, define the information that comes into the method, and optionally define the information that comes back out. Let s call the method ReadNumbersFromFile, since that s what it s going to do. Its input will be a text string containing the filename, and it will return an array of double-precision floating-point numbers. The method declaration, which will go inside our Program class, will look like this:

static double[] ReadNumbersFromFile(string fileName)

Listing 3-9 shows an example of how a dialog with list widgets is set up. First, a layout is created along with the widgets two list widgets and two buttons for moving items between the lists. After that, the buttons are connected to slots in the dialog class that perform the actual moving of the items before the list is populated. Figure 3-16 shows the dialog with the lists being used. Listing 3-9. Creating and populating the list widgets ListWidgetDialog::ListWidgetDialog() : QDialog() { QPushButton *left, *right; QGridLayout *layout = new QGridLayout( this ); layout->addWidget( left = new QPushButton( "<<" ), 0, 1 ); layout->addWidget( right = new QPushButton( ">>" ), 1, 1 ); layout->addWidget( leftList = new QListWidget, 0, 0, 3, 1 ); layout->addWidget( rightList = new QListWidget, 0, 2, 3, 1 ); connect( left, SIGNAL(clicked()), this, SLOT(moveLeft()) ); connect( right, SIGNAL(clicked()), this, SLOT(moveRight()) ); QStringList items; items << "Argentine" << "Brazilian" << "South African" << "USA West" << "Monaco" << "Belgian" << "Spanish" << "Swedish" << "French" << "British" << "German" << "Austrian" << "Dutch" << "Italian" << "USA East" << "Canadian"; leftList->addItems( items ); }