Qt开发笔记

Qt - Windodw识别设备插拔事件

Winodws系统消息结构：#include <qt_windows.h>

LRESULT CALLBACK WindowProc(
  HWND   hwnd,     // handle to window 
  UINT   uMsg,     // WM_DEVICECHANGE
  WPARAM wParam,   // device-change event
  LPARAM lParam ); // event-specific data

设备插入/拔出：#include <Dbt.h> msg->wParam

Value	Meaning
DBT_DEVICEARRIVAL	A device or piece of media has been inserted and is now available.
DBT_DEVICEREMOVECOMPLETE	A device or piece of media has been removed.

设备接入类型：msg->lParam 强制转换

Value	Meaning
DBT_DEVTYP_DEVICEINTERFACE 0x00000005	Class of devices. This structure is a DEV_BROADCAST_DEVICEINTERFACE structure.
DBT_DEVTYP_HANDLE 0x00000006	File system handle. This structure is a DEV_BROADCAST_HANDLE structure.
DBT_DEVTYP_OEM 0x00000000	OEM- or IHV-defined device type. This structure is a DEV_BROADCAST_OEM structure.
DBT_DEVTYP_PORT 0x00000003	Port device (serial or parallel). This structure is a DEV_BROADCAST_PORT structure.
DBT_DEVTYP_VOLUME 0x00000002	Logical volume. This structure is a DEV_BROADCAST_VOLUME structure.

CyAPI：官方lib使用MinGW编译，无法使用MSVC编译调用。

QString

https://doc.qt.io/qt-5/qstring.html

QString hex to unsigned char

Hexadecimal QString representation to Unsigned char array

unsigned char myBuffer[2];
Qstring hexStr = "0x1234";
bool ok = false;
myBuffer[0] = (unsigned char)hexstr.midRef(2,2).toUShort(&ok, 16)
myBuffer[1] = (unsigned char)hexstr.midRef(4,2).toUShort(&ok, 16)

QString 基本操作

在Qt5中，right()/left()/mid()是深拷贝，返回一个字符串中的n个字符的字符串。rightRef()/leftRef()/midRef()则是返回对其的引用。

n > str.length : return null string / reference
n < str.length : starting at the given position
n = -1(default): return all string / reference

QString str = "hello-world!";
int idx = str.lastIndexOf("-");
str.replace("h", "H");
str.right(idx-1);
str.left(idx);
str.mid(idx, 5); //mid(star_pos, size)

QCharts

https://www.jianshu.com/p/b3bdd88f490c

改变画笔颜色/宽度

How to change QLineSeries width?

单独指定画笔颜色+宽度

QPen pen = series->pen();
pen.setWidth(1);
pen.setBrush(QBrush("red")); // or just pen.setColor("red");
series->setPen(pen);

继承系统默认颜色，在chart->addSeries(series);之后设置画笔

QChart *chart = new QChart();
chart->addSeries(series); // addSeries must be called first

QPen pen = series->pen();
pen.setWidth(1);
series->setPen(pen);

QSpinBox

按位数补齐0：重载QSpinBox - textFromValue

#ifndef PADDINGZEROSPINBOX_H
#define PADDINGZEROSPINBOX_H
#include <QSpinBox>

class Padding4ZeroSpinBox: public QSpinBox
{
    Q_OBJECT
public:
    Padding4ZeroSpinBox();
    explicit Padding4ZeroSpinBox(QWidget *parent = nullptr){};

protected:
    virtual QString textFromValue(int val) const{
      //set padding str '0' and size 4
      QString val_str = QStringLiteral("%1").arg(val, 4, 16, QChar('0'));
      return val_str.left(4);
    }
};
#endif // PADDINGZEROSPINBOX_H

设置前缀/后缀/当前值

1 2	ui->my_spinbox->setPrefix("0x"); ui->my_spinbox->setValue("0xFF");

QTabWidget

改变背景色

How to set only QTabWidget background color stylesheet

QtDesigner -> TabWidget ->styleSheet属性中设置：在样式表中用’#’指定对象，子对象将不会继承样式表

1	#objectName {background-color: rgb(240,240,240);}

Qt打包程序

打包程序的一些已知问题：https://cloud.tencent.com/developer/article/1516768

无法定位程序输入点?xxx@Qxxx@@xxxx@@@xxxxx于动态链接库xx.exe上

调整系统环境变量该编译环境的环境变量顺序靠前即可。

eg.Qt有MinGW+MSVC2015的两个环境编辑：如果用MSVC2015编译打包的环境，则将MSVC2015的环境变量的顺序置于MinGW之前(必要的时候，越靠前越好)