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

The user interface is implemented in the ImageDialog class. The public part of the class declaration, shown in Listing 13-6, consists of a constructor and a set of slots, where each slot represents a user action. What can the user do Looking at the class declaration and Figure 13-1 you can see a number of possible user actions. The following lists them and their corresponding slots: Move between the images: nextClicked and previousClicked Change the selection in the list of tags: tagsChanged Add a new image: addImageClicked Add a new tag: addTagClicked Add to this list the inherited tasks, such as being able to close the dialog to exit the application. Listing 13-6. Half of the ImageDialog class declaration class ImageDialog : public QDialog { Q_OBJECT public: ImageDialog(); private slots: void nextClicked(); void previousClicked(); void tagsChanged(); void addImageClicked(); void addTagClicked(); ... };

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The overload of GetFiles we re calling takes the directory we d like to search, a filter (in the standard command-line form), and a value from the SearchOption enumeration, which determines whether to recurse down through all the subfolders.

We re using LINQ to Objects to build a list of all the files we require. As you saw in 8, a query with multiple from clauses works in a similar way to nested foreach loops. The code in Example 11-5 will end up calling GetFiles for each directory passed on the command line, and it will effectively concatenate the results of all those calls into a single list of files.

The GetFiles method returns the full path for each file concerned, but when it comes to finding matches, we just want the filename. We can use the Path class to get the filename from the full path.

After reading this chapter, you should have a good grasp of how to start implementing your own data-aware web applications that use Atlas to provide Ajax-style asynchrony In the next chapter, you ll start looking at another client-side library one that provides additional user interface functionality, or glitz, to your applications..

The other half of the class declaration tells you something about how the application works (the source code is shown in Listing 13-7). It starts with four private support methods: selectedTags, updateImages, updateTags, and updateCurrentImage. You will look at each one of them soon. After the methods, the Designer-generated user interface class is included as ui before the member variables used for keeping track of the images. The imageIds list contains the id values for the images that are shown according to the selected tags. The currentImage is an index into the imageIds list that indicates which image is active. Finally, the images variable is an instance of the ImageCollection class that handles the database. Listing 13-7. The private half of the ImageDialog class declaration class ImageDialog : public QDialog { ... private: QStringList selectedTags(); void updateImages(); void updateTags(); void updateCurrentImage(); Ui::ImageDialog ui; QList<int> imageIds; int currentImage; ImageCollection images; };

The Path class provides methods for manipulating strings containing file paths. Imagine we have the path c:\directory1\directory2\MyFile.txt. Table 11-1 shows you how you can slice that with various different Path methods.

c:\directory1\directory2 .txt (note the leading . ) MyFile.txt MyFile c:\directory1\directory2\MyFile.txt c:\

What if we use a network path Table 11-2 shows the results of the same methods when applied to this path:

The ImageDialog was created using Designer, so you can start by having a look at it (Figure 13-3 shows the basic design of the dialog). Apart from the text properties and the names of the different widgets, the only property that was altered is the SelectionMode of the QListWidget; it was set to MultiSelection.

Notice how the path root includes the network hostname and the share name. What happens if we don t use a full path, but one relative to the current directory And what s the current directory anyway

The framework maintains a process-wide idea of the current working directory, which is the root path relative to which any file operations that do not fully qualify the path are made. The Directory class (as you might imagine) gives us the ability to manipulate it. Rather than a static property, there are two static methods to query and set the current value: GetCurrentDirectory and SetCurrentDirectory. Example 11-6 shows a call to the latter.

Directory.SetCurrentDirectory(@"c:\");

Figure 13-3. The design of the image dialog Figure 13-4 shows the object hierarchy of the dialog (you can also see the names of the different widgets). The only thing not apparent is that the layout of the dialog itself is a grid layout.

Table 11-3 shows the results we d get if we passed @"directory2\MyFile.txt" to the various Path methods after having run the code in Example 11-6. As you can see, most of the results reflect the fact that we ve not provided a full path, but there s one exception: GetFullPath uses the current working directory if we provide it with a relative path.