.NET/Java PDF, Tiff, Barcode SDK Library

Qt offers three different default views: a tree, a list, and a table. In the 2 phone book example you encountered the list view by way of the QListWidget. The QListWidget class is a specialized version of QListView, but QListWidget contains the data shown in the list, whereas QListView accesses its data from a model. The QListWidget is sometimes referred to as a convenience class because it is less flexible, but is more convenient in less complex situations when compared with using the QListView and a model. In the same way that the list widget relates to the list view, the QTreeWidget-QTreeView and QTableWidget-QTableView pairs relate. Let s start with an example showing how to create a model, populate it, and show it using all three views. To keep matters simple, it is created from a single main function. The first thing to do is to create the widgets. In Listing 5-1, you can see that the QTreeView, QListView, and QTableView are created and put into a QSplitter. A splitter is a widget that puts movable bars between its children. This means that the user can divide the space between the tree, list, and table freely. You can see the splitter in action in Figure 5-3. Listing 5-1. Creating the views and putting them in a splitter QTreeView *tree = new QTreeView; QListView *list = new QListView; QTableView *table = new QTableView; QSplitter splitter; splitter.addWidget( tree ); splitter.addWidget( list ); splitter.addWidget( table );

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This produces:

2895729

Another one for integer types, hexadecimal formatting, shown in Example 10-11, represents numbers as a string of hex digits (0 9, A F).

Figure 5-3. The tree, list, and table can be resized by using the splitter. The top window is the default starting state, whereas the splitter bars have been moved in the lower window. When the widgets are created, you have to create and populate a model. To get started, the QStandardItemModel is used, which is one of the standard models shipped with Qt. Listing 5-2 shows how the model is populated. The population process consists of three loops: rows (r), columns (c), and items (i). The loops create five rows of two columns, in which the first column has three items as children. Listing 5-2. Creating and populating the model QStandardItemModel model( 5, 2 ); for( int r=0; r<5; r++ ) for( int c=0; c<2; c++) { QStandardItem *item = new QStandardItem( QString("Row:%1, Column:%2").arg(r).arg(c) ); if( c == 0 ) for( int i=0; i<3; i++ ) item->appendRow( new QStandardItem( QString("Item %1").arg(i) ) ); model.setItem(r, c, item); }

int amount = 256; string text = amount.ToString("X");

You can embed the arguments {0}, {1}, and so on, in this string and have the relevant properties assigned at runtime In this case, you have bound to the value of the checkbox, and this value is transformed into a string This then gets inserted into the string at the position of the argument So, the string Checkbox is {0} will become Checkbox is True or Checkbox is False The underlying Boolean value of the checkbox is transformed into the string True or False..

This produces the output:

As with the decimal format string, you can specify a number to indicate the total number of digits to which to pad the number, as shown in Example 10-12.

int amount = 256; string text = amount.ToString("X4");

Let s have a close look at how the population is made. First, QStandardItemModel is created, and the constructor is told to make it five rows by two columns. Then a pair of loops for the rows and columns is run where a QStandardItem is created for each position. This item is put in the model by using the setItem(int, int, QStandardItem*) method. For all items in the first column, where c equals 0, three new QStandardItem objects are created and put as children to the item using the appendRow(QStandardItem*) method. Figure 5-4 shows how the model looks in a tree view. The items for each column and row position are shown as a table. In the table, the second row has been expanded, revealing the three child items.

This produces the output:

Notice that the method doesn t prepend a 0x or similar; so there is nothing to distinguish this as a hex string, if you happen to hit a value that does not include the digits A F. (The convention of preceding hexadecimal values with 0x is common in C family languages, which is why C# supports it for numeric constants, but it s not universal. VB.NET uses the prefix &H, for example. All .NET languages share the same numeric types and formatting services, so if they printed hex numbers with a C# prefix, that would be annoying for users of other languages. If you want a prefix, you have to add it yourself.)

WPF and Silverlight are related technologies for building user interfaces in NET Although they are aimed at two significantly different scenarios, they share so many concepts and features that it makes sense to discuss both of them at the same time almost everything in this chapter applies to both WPF and Silverlight As its name suggests, the Windows Presentation Foundation (WPF) is for building interactive applications that run on Windows WPF applications typically run as standalone applications, requiring an installation step to get them onto the target machine, as they may need prerequisites to be installed first (WPF is NET-based, so it requires the NET Framework to be installed) This means they are deployed like old-school Windows desktop applications However, WPF makes it easy for applications to exploit the graphical potential of modern computers in a way that is extremely hard to achieve with more traditional Windows UI technologies.