相關資料：

https://blog.csdn.net/weixin_30608131/article/details/95468028?utm_medium=distribute.pc_relevant.none-task-blog-searchFromBaidu-1.control&depth_1-utm_source=distribute.pc_relevant.none-task-blog-searchFromBaidu-1.control

mainwindow.cpp

 1 #include "mainwindow.h"
 2 #include "ui_mainwindow.h"
 3
 
 
 4 MainWindow::MainWindow(QWidget *parent)
 5     : QMainWindow(parent)
 6     , ui(new Ui::MainWindow)
 7 {
 8     ui->setupUi(this);
 9 
10     // 設定垂直滾動條基本樣式
11     ui->scrollArea->setStyleSheet("QScrollBar:vertical"
12                                                        "{"
13                                                        "
 
width:8px;"
14                                                        "background:rgba(255,0,0,0%);"
15                                                        "margin:0px,0px,0px,0px;"
16 //                                                       "padding-top:9px;"// 留出9px給上面和下面的箭頭
17 //                                                       "padding-bottom:9px;"
 

18                                                        "}"
19                                                        "QScrollBar::handle:vertical"
20                                                        "{"
21                                                        "width:8px;"
22                                                        "background:rgba(255,0,0,25%);"
23                                                        " border-radius:4px;"// 滾動條兩端變成橢圓
24                                                        "min-height:20;"
25                                                        "}"
26                                                        "QScrollBar::handle:vertical:hover"
27                                                        "{"
28                                                        "width:8px;"
29                                                        "background:rgba(255,0,0,50%);"// 滑鼠放到滾動條上的時候，顏色變深
30                                                        " border-radius:4px;"
31                                                        "min-height:20;"
32                                                        "}"
33                                                        "QScrollBar::add-line:vertical"
34                                                        "{"
35                                                        "height:9px;width:8px;"
36                                                        "border-image:url(:/images/a/3.png);"// 這個應該是設定下箭頭的，3.png就是箭頭
37                                                        "subcontrol-position:bottom;"
38                                                        "}"
39                                                        "QScrollBar::sub-line:vertical"
40                                                        "{"
41                                                        "height:9px;width:8px;"
42                                                        "border-image:url(:/images/a/1.png);" // 設定上箭頭
43                                                        "subcontrol-position:top;"
44                                                        "}"
45                                                        "QScrollBar::add-line:vertical:hover"
46                                                        "{"
47                                                        "height:9px;width:8px;"
48                                                        "border-image:url(:/images/a/4.png);"// 當滑鼠放到下箭頭上的時候
49                                                        "subcontrol-position:bottom;"
50                                                        "}"
51                                                        "QScrollBar::sub-line:vertical:hover"
52                                                        "{"
53                                                        "height:9px;width:8px;"
54                                                        "border-image:url(:/images/a/2.png);"// 當滑鼠放到下箭頭上的時候
55                                                        "subcontrol-position:top;"
56                                                        "}"
57                                                        "QScrollBar::add-page:vertical,QScrollBar::sub-page:vertical"// 當滾動條滾動的時候，上面的部分和下面的部分
58                                                        "{"
59                                                        "background:rgba(255,0,0,10%);"
60                                                        "border-radius:4px;"
61                                                        "}"
62                                                        );
63 }
64 
65 MainWindow::~MainWindow()
66 {
67     delete ui;
68 }