embedded linux QT Development (III.)--GUI principle Analysis First,
command-line programs
command-line programs are process-oriented programming.
Features of the command-line program:
A. Execution based on sequential structure
B, the program execution process does not need to interact with the user
C, program execution end gives the final running result
Command-line Application occasions:
A, single-task occasions
B, no interaction, simple interaction occasions
C, server applications
Second,
GUI Program
Features of GUI programs:
A, a message-driven model-based program
B, program execution relies on user interaction process
C, real-time response to user actions during program execution
D, the general program will not be actively exited after implementation
GUI program for the occasion:
A, multi-tasking occasions
B, strong user interaction occasions
C, non-professional computer users
GUI program run mode:
650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M02/88/49/wKioL1ft7r2iDH26AABpkgB3ps4387.png "title=" Picture 1.png "alt=" Wkiol1ft7r2idh26aabpkgb3ps4387.png "/>
GUI program Message processing model:
650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M00/88/4C/wKiom1ft7tuRz6KpAABxeDFvUoE344.png "title=" Picture 2.png "alt=" Wkiom1ft7turz6kpaabxedfvuoe344.png "/>
First,
GUI Program Development principle
modern operating systems are supported GUI program development, features are as follows:
A, the operating system provides native SDK support GUI program development
B, GUI program development is the mainstream technology of modern operating system
C, the same principle of GUI development on different operating systems
D. Different GUI SDKs on different operating systems
GUI Program Development principle:
A, the GUI program creates a message queue at run time
B, The system kernel translates user actions into corresponding program messages
C, The program needs to process messages in the message queue in real time during Operation
D, The program is stuck when there is no message in the queue
GUI Program development process:
A, create window, window element GUI interface
B, in the message processing function according to the program message to make different corresponding
Iv. The nature of QT
1. Object-oriented GUI programming
The operating system provides the functions required to create interface elements, and in turn calls functions of different functions to create interface elements, but the native functions provided by the operating system cannot be directly mapped to interface elements. Based on object-oriented programming, the interface elements are abstracted into classes, andthe process of creating GUI interfaces is the process of combining different interface elements.
2.
The nature of QT
QT is a set of GUI component libraries developed using object-oriented programming, QT encapsulates the GUI details of different operating systems in the class, and provides a set of cross-platform classes for GUI program development.
QT follows the classic GUI program development model.
Five,
QT Instance 1.
Example Source
#include <QApplication>
#include <QMainWindow>
#include <QPushButton>
int main (int argc, char* argv[])
{
Qapplication A (argc, argv);
Qmainwindow W;
Qpushbutton b (&w);
B.settext ("Hello qt!");
W.show ();
return A.exec ();
}
2.
QT Development Environment Command-line compilation
A. Enter the QT development environment command line
650) this.width=650; "src=" Http://s4.51cto.com/wyfs02/M01/88/4C/wKiom1ft7wLQCgFHAABBriUAdQs869.png "title=" Picture 3.png "alt=" Wkiom1ft7wlqcgfhaabbriuadqs869.png "/>
Click qt 4.7.4 command prompt into the QT development environment.
B. Enter the directory where the source program is located
C. Generate engineering documents according to source code
Qmake-project
build process file Xxxxx.pro
D. Generate makefile Files according to engineering documents
Qmake
Build Makefile, Makefile.debug, makefile.release files and release, Debug directories
E, compiling
Make
compile and build the executable file Xxx.exe
3.
QT IDE development environment
Qt Creator is a visual integrated development environment for QT.
How to debug the QT creator environment:
A, Log Debug Method
Add a certain print statement to the code to print out the program state and the value of the key variable
Log printing needs to add # include <QDebug>
Qdebug () << "Hello";
B, breakpoint Debugging method
in the QT Creator Development environment when you open a project, you can set a breakpoint on the appropriate line of code, and when the program runs to a breakpoint, it pauses to run, and when the conditional breakpoint is set, the program pauses to run when the condition is met.
This article from "Life is endless, struggle not only" blog, declined reprint!
Embedded Linux QT Development (iii)--gui principle analysis