Dr. Dobb's Journal - June 2008 - (Page 32) d06espen_p4ds 4/11/08 9:16 AM Page 32 Core Technology QT AND WINDOWS CE continued from page 30 PreviewWindow() : QWidget(), current(1) { ui.setupUi(this); } The PreviewWindow class has the following members: Ui::ImageViewer ui; QStringList imageFileList; QPixmap mainPixmap; int current; UI::ImageViewer ui is an instance of the class generated by Qt Designer. By calling ui.setupUi(this), I initialize my own class (the PreviewWindow class) with the GUI I created in Qt Designer. At this point, I can run the application. While it would look like what I designed in Qt Designer, I also need to connect the widgets with program logic to make the application functional. When you change one widget in GUI programming, you often want another widget to be notified. Generally, you want objects of any kind to be able to communicate with one another. For example, if users click previousButton, you want PreviewWindow’s previousImage() function to be called. Qt’s solution for this is “signals” and “slots” (similar to Delegates/Events in C#): • Signals are emitted when a particular event occurs. Qt’s widgets have many predefined signals, but you can always subclass widgets to add your own signals to them. • Slots are functions called in response to particular signals. Qt’s widgets have many predefined slots, but it is common practice to subclass widgets and add your own slots so that you can handle the signals you’re interested in. For the PreviewWindow class, I’ve added these slots: void void void void void nextImage() { } previousImage() { } changeDirectory() { } toggleStyleSheet() { } setTranslator(QObject *object) { } To connect the signals from the different widgets to these slots, you only need to call the connect() function in the constructor of the widget. Here, I connect the clicked() signals from previousButton and nextButton: Figure 1: Qt Image Viewer with custom style running on Windows Mobile 6.0. 32 Dr. Dobb’s Journal l www.ddj.com l June 2008 http://www.programmingresearch.com http://www.programmingresearch.com http://www.ddj.com
Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - June 2008 Dr. Dobb's Journal - June 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries There Must Be Contest Conversations Building a Test Harness for RTOS QT and Windows CE Software to Hardware Parallelization Performance Portable C++ Effective Concurrency The Agile Edge Swaine's Flames Dr. Dobb's Journal - June 2008 Dr. Dobb's Journal - June 2008 - Dr. Dobb's Journal - June 2008 (Page Cover1) Dr. Dobb's Journal - June 2008 - Dr. Dobb's Journal - June 2008 (Page Cover2) Dr. Dobb's Journal - June 2008 - Dr. Dobb's Journal - June 2008 (Page 1) Dr. Dobb's Journal - June 2008 - Dr. Dobb's Journal - June 2008 (Page 2) Dr. Dobb's Journal - June 2008 - Dr. Dobb's Journal - June 2008 (Page 3) Dr. Dobb's Journal - June 2008 - Contents (Page 4) Dr. Dobb's Journal - June 2008 - Contents (Page 5) Dr. Dobb's Journal - June 2008 - Friday Night Fish Fry (Page 6) Dr. Dobb's Journal - June 2008 - Friday Night Fish Fry (Page 7) Dr. Dobb's Journal - June 2008 - Friday Night Fish Fry (Page 8) Dr. Dobb's Journal - June 2008 - Friday Night Fish Fry (Page 9) Dr. Dobb's Journal - June 2008 - Alia Vox (Page 10) Dr. Dobb's Journal - June 2008 - Alia Vox (Page 11) Dr. Dobb's Journal - June 2008 - Alia Vox (Page 12) Dr. Dobb's Journal - June 2008 - Alia Vox (Page 13) Dr. Dobb's Journal - June 2008 - Developer Diaries (Page 14) Dr. Dobb's Journal - June 2008 - Developer Diaries (Page 15) Dr. Dobb's Journal - June 2008 - There Must Be Contest (Page 16) Dr. Dobb's Journal - June 2008 - There Must Be Contest (Page 17) Dr. Dobb's Journal - June 2008 - There Must Be Contest (Page 18) Dr. Dobb's Journal - June 2008 - There Must Be Contest (Page 19) Dr. Dobb's Journal - June 2008 - Conversations (Page 20) Dr. Dobb's Journal - June 2008 - Conversations (Page 21) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 22) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 23) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 24) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page IBM-1) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page IMB-2) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 25) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 26) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 27) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 28) Dr. Dobb's Journal - June 2008 - Building a Test Harness for RTOS (Page 29) Dr. Dobb's Journal - June 2008 - QT and Windows CE (Page 30) Dr. Dobb's Journal - June 2008 - QT and Windows CE (Page 31) Dr. Dobb's Journal - June 2008 - QT and Windows CE (Page 32) Dr. Dobb's Journal - June 2008 - QT and Windows CE (Page 33) Dr. Dobb's Journal - June 2008 - QT and Windows CE (Page 34) Dr. Dobb's Journal - June 2008 - QT and Windows CE (Page 35) Dr. Dobb's Journal - June 2008 - Software to Hardware Parallelization (Page 36) Dr. Dobb's Journal - June 2008 - Software to Hardware Parallelization (Page 37) Dr. Dobb's Journal - June 2008 - Software to Hardware Parallelization (Page 38) Dr. Dobb's Journal - June 2008 - Software to Hardware Parallelization (Page 39) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 40) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 41) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 42) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 43) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 44) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 45) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 46) Dr. Dobb's Journal - June 2008 - Performance Portable C++ (Page 47) Dr. Dobb's Journal - June 2008 - Effective Concurrency (Page 48) Dr. Dobb's Journal - June 2008 - Effective Concurrency (Page 49) Dr. Dobb's Journal - June 2008 - Effective Concurrency (Page 50) Dr. Dobb's Journal - June 2008 - Effective Concurrency (Page 51) Dr. Dobb's Journal - June 2008 - The Agile Edge (Page 52) Dr. Dobb's Journal - June 2008 - The Agile Edge (Page 53) Dr. Dobb's Journal - June 2008 - The Agile Edge (Page 54) Dr. Dobb's Journal - June 2008 - The Agile Edge (Page 55) Dr. Dobb's Journal - June 2008 - Swaine's Flames (Page 56) Dr. Dobb's Journal - June 2008 - Swaine's Flames (Page Cover3) Dr. Dobb's Journal - June 2008 - Swaine's Flames (Page Cover4)
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