主要思路：

在QT designer 中繪制QLabel控件

自定義類繼承QLabel類，並提升至控件

提升至

生成隨機數

重寫paintEvent繪制圖形

重寫mousePressEvent刷新驗證碼

註意當窗口大小、焦點發生變化時均可觸發paintEvent函數。

繪制控件

在窗口中添加QLabel控件並布局

自定義驗證碼類

.h文件

 1 #pragma once
 2 #include <QLabel>
 3 #include <QPaintEvent>
 4 #include <QPainter>
 5 #include <QTime>
 6
 
 class VerificationCodeLabel : public QLabel
 7 {
 8 public:
 9     VerificationCodeLabel(QWidget *parent = 0);
10     ~VerificationCodeLabel();
11 protected:
12     //重寫繪制事件,以此來生成驗證碼
13     void paintEvent(QPaintEvent *event);
14     void mousePressEvent(QMouseEvent *ev);
15 private:
16     const int letter_number = 4
 
;//產生字符的數量
17     int noice_point_number;//噪點的數量
18     //生成驗證碼
19     void produceVerificationCode();
20     //產生隨機的字符
21     QChar produceRandomLetter();
22     //產生隨機的顏色
23     void produceRandomColor();
24 
25     QChar *verificationCode;
26     QColor *colorArray;
27 };

.cpp文件

 1 VerificationCodeLabel::VerificationCodeLabel(QWidget *parent): QLabel(parent)
 
 2 {
 3     //生成隨機種子
 4     qsrand(QTime::currentTime().second() * 1000 + QTime::currentTime().msec());
 5     colorArray = new QColor[letter_number];
 6     verificationCode = new QChar[letter_number];
 7     noice_point_number = this->width()*4;
 8 }
 9 
10 VerificationCodeLabel::~VerificationCodeLabel()
11 {
12 
13 }
14 //重寫繪制事件,以此來生成驗證碼
15 void VerificationCodeLabel::paintEvent(QPaintEvent *event)
16 {
17     QPainter painter(this);
18     QPoint p;
19     //產生4個不同的字符
20     produceVerificationCode();
21     //產生4個不同的顏色
22     produceRandomColor();
23     //繪制驗證碼
24     for (int i = 0; i < letter_number; ++i)
25     {
26         p.setX(i*(this->width() / letter_number) + this->width() / 16);
27         p.setY(this->height()/1.5);
28         painter.setPen(colorArray[i]);
29         painter.drawText(p, QString(verificationCode[i]));
30     }
31     //繪制噪點
32     for (int j = 0; j < noice_point_number; ++j)
33     {
34         p.setX(qrand() % this->width());
35         p.setY(qrand() % this->height());
36         painter.setPen(colorArray[j % 4]);
37         painter.drawPoint(p);
38     }
39     return;
40 }
41 //這是一個用來生成驗證碼的函數
42 void VerificationCodeLabel::produceVerificationCode()
43 {
44     for (int i = 0; i < letter_number; ++i)
45         verificationCode[i] = produceRandomLetter();
46     return;
47 }
48 //產生一個隨機的字符
49 QChar VerificationCodeLabel::produceRandomLetter()
50 {
51     QChar c;
52     int flag = qrand() % letter_number;
53     switch (flag)
54     {
55     case 0:
56         c = ‘0‘ + qrand() % 10;
57         break;
58     case 1:
59         c = ‘A‘ + qrand() % 26; 
60         break;
61     case 2:
62         c = ‘a‘ + qrand() % 26; 
63         break;
64     default:
65         c = ‘0‘ + qrand() % 10;
66         break;
67     }
68     return c;
69 }
70 //產生隨機的顏色
71 void VerificationCodeLabel::produceRandomColor()
72 {
73     for (int i = 0; i < letter_number; ++i)
74         colorArray[i] = QColor(qrand() % 255, qrand() % 255, qrand() % 255);
75     return;
76 }
77 
78 void VerificationCodeLabel::mousePressEvent(QMouseEvent *ev)
79 {
80     update();
81 }

自定義類提升至控件

運行結果

參考：

https://blog.csdn.net/wjh_init/article/details/79163275

QT實現簡單驗證碼