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author | Morten Engvoldsen <morten.engvoldsen@nokia.com> | 2009-11-09 12:02:51 (GMT) |
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committer | Morten Engvoldsen <morten.engvoldsen@nokia.com> | 2009-11-09 12:02:51 (GMT) |
commit | a7577f8c3ae3a025384d8d19fdf3575ef141a70b (patch) | |
tree | 9c2f7c74f7aabedcef46e435aa8ada3f3708fb10 /doc | |
parent | d9c5a6828e0f5c846aeef214f2fe0a9de48072dc (diff) | |
download | Qt-a7577f8c3ae3a025384d8d19fdf3575ef141a70b.zip Qt-a7577f8c3ae3a025384d8d19fdf3575ef141a70b.tar.gz Qt-a7577f8c3ae3a025384d8d19fdf3575ef141a70b.tar.bz2 |
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Diffstat (limited to 'doc')
-rw-r--r-- | doc/src/examples/googlesuggest.qdoc | 148 | ||||
-rw-r--r-- | doc/src/images/googlesuggest-example.png | bin | 18809 -> 9006 bytes |
2 files changed, 145 insertions, 3 deletions
diff --git a/doc/src/examples/googlesuggest.qdoc b/doc/src/examples/googlesuggest.qdoc index bec242d..f3693e9 100644 --- a/doc/src/examples/googlesuggest.qdoc +++ b/doc/src/examples/googlesuggest.qdoc @@ -43,10 +43,152 @@ \example network/googlesuggest \title Google Suggest Example - The Google Suggest example shows how to use the network access manager - to get the list of suggested search terms from Google. + The Google Suggest example demonstrates how to use the QNetworkAccessManager + class to obtain a list of suggestions from the Google search engine as the + user types into a QLineEdit. \image googlesuggest-example.png - \note The Google Suggest suggestion service is a registered trademark of Google Inc. + The application makes use of the \c get function in +QNetworkAccessManager to post a request and obtain the result of the search +query sent to the Google search engine. The results returned are listed as +clickable links appearing below the search box as a drop-down menu. + +The widget is built up by a QLineEdit as the search box, and a QTreeView +used as a popup menu below the search box. + +\section1 GSuggestCompletion Class Declaration + +This class implements an event filter and a number of functions to display +the search results and to determent when and how to perform the search. + +\snippet examples/network/googlesuggest/googlesuggest.h 1 + +The class connects to a QLineEdit and uses a QTreeWidget to display the +results. A QTimer controls the start of the network requests that are +executed using a QNetworkAccessManager. + +\section1 GSuggestCompletion Class Implementation + +We start by defining a constant containing the URL to be used in the Google +queries. This is the basis for the query. The letters typed into the search +box will be added to the query to perform the search itself. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 1 + +In the constructor, we set the parent of this GSuggestCompletion instance +to be the QLineEdit passed in. For simplicity, the QLineEdit is also stored +in the explicit \c editor member variable. + +We then create a QTreeWidget as a toplevel widget and configure the various +properties to give it the look of a popup widget. + +The popup will be populated by the results returned from Google. We set +the number of columns to be two, since we want to display both the +suggested search term and the number of hits it will trigger in the search +engine. + +Furthermore, we install the GSuggestCompletion instance as an event filter +on the QTreeWidget, and connect the \c itemClicked() signal with the \c +doneCompletion() slot. + +A single-shot QTimer is used to start the request when the user has stopped +typing for 500 ms. + +Finally, we connect the networkManagers \c finished() signal with the \c +handleNetworkData() slot to handle the incoming data. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 2 + +Since the QTreeWidget popup has been instantiated as a toplevel widget, the +destructor has to delete it explicitly from memory to avoid a memory leak. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 3 + +The event filter handles mouse press and key press events that are +delivered to the popup. For mouse press events we just hide the popup and +return focus to the editor widget, and then return true to prevent further +event processing. + +Key event handling is implemented so that Enter and Return execute the +selected link, while the Escape key hides the popup. Sine we want to be +able to navigate the list of suggestions using the different navigation +keys on the keyboard we let Qt continue regular event processing for those +by returning false from the eventFilter reimplementation. + +For all other keys, the event will be passed on to the editor widget and the +popup is hidden. This way the user's typing will not be interrupted by the +popping up of the completion list. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 4 + +The \c showCompletion() function populates the QTreeWidget with the results +returned from the query. It takes two QStringLists, one with the suggested +search terms and the other with the corresponding number of hits. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 5 + +A QTreeWidgetItem is created for each index in the list and inserted into +the QTreeWidget. Finally, we adjust position and size of the popup to make +sure that it pops up in the correct position below the editor, and show it. + +The \c doneCompletion() function, which is called by the event filter when +either Enter or Return keys are pressed, stops the timer to prevent further +requests and passes the text of the selected item to the editor. We then +make the \c editor QLineEdit emit the returnPressed() signal, to which the +application can connect to open the respective web page. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 6 + +The \c autoSuggest() slot is called when the timer times out, and uses the +text in the editor to build the complete search query. The query is then +passed to the QNetworkAccessManager's \c get() function to start the +request. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 7 + +The function \c preventSuggest() stops the timer to prevent further +requests from being started. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 8 + +When the network request is finished, the QNetworkAccessManager delivers the +data received from the server through the networkReply object. + +\snippet examples/network/googlesuggest/googlesuggest.cpp 9 + +To extract the data from the reply we use the \c readAll() function, which +is inherited from QIODevice and returns a QByteArray. Since this data is +encoded in XML we can use a QXmlStreamReader to traverse the data and +extract the search result as QStrings, which we can stream into two +QStringLists used to populate the popup. + +Finally, we schedule the QNetworkReply object for deletion using the \c +deleteLater function. + +\section1 SearchBox Class Declaration + +The SearchBox class inherits QLineEdit and adds the protected slot \c +doSearch(). + +A \c GSuggestCompletion member provides the SearchBox with the request +functionality and the suggestions returned from the Google search engine. + +\snippet examples/network/googlesuggest/searchbox.h 1 + +\section1 SearchBox Class Implementation + +The search box constructor instantiates the GSuggestCompletion object and +connects the returnPressed() signal to the doSearch() slot. + +\snippet examples/network/googlesuggest/searchbox.cpp 1 + +The function \c doSearch() stops the completer from sending any further +queries to the search engine. + +Further, the function extracts the selected search phrase and opens it in +the default web browser using QDesktopServices. + +\snippet examples/network/googlesuggest/searchbox.cpp 2 + */ diff --git a/doc/src/images/googlesuggest-example.png b/doc/src/images/googlesuggest-example.png Binary files differindex 4ef072a..477d444 100644 --- a/doc/src/images/googlesuggest-example.png +++ b/doc/src/images/googlesuggest-example.png |