A simple QT drawing program under Ubuntu

Tag: Call false. com source file creat setw PAC vector BSP

Original: http://www.linuxidc.com/Linux/2011-08/41220.htm

When I was learning MFC, the most classic example of getting started is the drawing program, which acts as the Hello World under the console application.

Now to start QT, can not help but nostalgia, so also wrote a drawing program, although simple, but also a prerequisite for the entry ah.

Environment

Os:ubuntu 11.04

IDE:QT Creator 2.2.1

qt:4.7.4 (32bit)

complier:gcc

1. Create a blank QT project

Files--New project or project--other projects--empty QT Project

For example, named Qt_instance_example.

2. Add a C + + source file

For example, named Main.cpp.

Add the following code

2. #include <qapplication>
4. #include <mypainterwidget.h>
8. int main (int argc,char** argv)
10. {
12. Qapplication A (ARGC,ARGV);
16. Mypainterwidget W (0);
18. W.show ();
20. return A.exec ();
22. }

The Mypainterwidget class here is a subclass of the Qwidget class we write ourselves to implement the drawing widgets.

Let's add this class and write its code.

3. Add a C + + class named Mypainterwidget

The. h file is as follows

2. #ifndef Mypainterwidget_h
4. #define MYPAINTERWIDGET_H
8. #include <QWidget>
10. #include <QPoint>
12. #include <vector>
16. using namespace std;
22. //Segment
24. typedef struct myline{
26. Qpoint Startpnt;
28. Qpoint Endpnt;
30. }myline;
34. class Mypainterwidget: public Qwidget
36. {
38. Public:
40. Mypainterwidget (qwidget* parent);
42. ~mypainterwidget ();
46. //Inheritance
48. void paintevent (qpaintevent* p);
50. void mousepressevent (qmouseevent *e);
52. void mousemoveevent (qmouseevent *e);
54. void mousereleaseevent (qmouseevent *e);
58. Qpoint Startpnt; //Starting point
60. Qpoint Endpnt; //End point
62. bool ispressed; //The mouse is pressed
66. Vector<myline*> lines; //Store all the segments www.linuxidc.com
68. };
72. #endif//Mypainterwidget_h

The. cpp file is as follows

2. #include "mypainterwidget.h"
4. #include <QString>
6. #include <QMessageBox>
8. #include <QPainter>
10. #include <QPen>
12. #include <QMouseEvent>
18. Mypainterwidget::mypainterwidget (qwidget* parent)
20. : Qwidget (parent) {
22. Setminimumsize (240,120);
24. Setmaximumsize (480,240);
26. This->setmousetracking (true);
28. This->ispressed = false;
30. }
34. Mypainterwidget::~mypainterwidget () {
38. }
42. void Mypainterwidget::p aintevent (qpaintevent*p) {
44. qpainter painter (this);
46. Qpen pen; //Create a brush
48. Pen.setcolor (Qt::d Arkcyan);
50. Pen.setwidth (5);
52. Painter.setpen (pen);
56. for (int i = 0;i<lines.size (); i++) {
58. myline* pLine = lines[i];
60. Painter.drawline (PLINE->STARTPNT,PLINE->ENDPNT);
62. }
64. }
68. void Mypainterwidget::mousepressevent (Qmouseevent *e) {
70. SetCursor (Qt::P ointinghandcursor);
72. STARTPNT = E->pos ();
74. ENDPNT = E->pos ();
76. This->ispressed = true;
78. //qstring msg = "(" +qstring::number (E->x ()) + "," +qstring::number (E->y ()) + ")";
80. //qmessagebox::warning (this,tr ("Warning"), Msg,qmessagebox::ok);
82. }
86. void Mypainterwidget::mousemoveevent (Qmouseevent *e) {
88. if (this->ispressed) {
90. ENDPNT = E->pos ();
94. myline* line = new myline; //put the new line into vector
96. LINE->STARTPNT = STARTPNT;
98. LINE->ENDPNT = ENDPNT;
100. this->lines.push_back (line);
104. Update (); //repainter,call paintevent
106. STARTPNT = ENDPNT;
108. }
110. }
114. void Mypainterwidget::mousereleaseevent (Qmouseevent *e) {
116. SetCursor (Qt::arrowcursor);
118. This->ispressed = false;
120. }

3. The results of the operation are as follows

A simple QT drawing program under Ubuntu