QT Development (10) - Some Skills Summary in the C++/Qt Development Process

From time to time, I will summarize some of the tips I have discovered, so that even if I forget it, I can find it back by flipping through the blog, which is also excellent.

1. C++

1. Modification of variables

auto: belongs to one-time storage, and its storage space can be repeatedly overwritten by several variables
register: stored in a general-purpose register
extern: can be referenced in all functions and program sections
static: stored at a fixed address in memory, valid during the entire program running

2. Display the conversion operator

static_case
dynameic_cast
const_cast
reinterpret_cast

3. The default value of bool

true=1
false=0

4. Binary output

    //进制输出
    int a = 1000;
    cout << "十进制："<< dec << a << endl;
    cout << "八进制：" << oct << a << endl;
    cout << "十六进制：" << hex << a << endl;

5. Ninety-nine multiplication table

    //九九乘法表
    for (int i = 1; i <= 9; i++)
    {
        for (int j = 1;j<=i;j++)
        {
            cout << i << " * " << j << " = " << i * j << " ";
        }
        cout << endl;
    }

6. Preprocessing commands

#define
#error
#if
#else
#elif
#endif  
#ifdef
#ifndef
#undef
#line
#pragma

7. Array length

C++ does not directly provide the length method of the array, we can calculate it like this

int main()
{
    int arr[] = { 1,5,9,10,9,2 };

    //方法一
    cout << "数组的长度:" << (end(arr) - begin(arr))<< endl;
    //方法二
    cout << "数组的长度:" << (sizeof(arr) / sizeof(arr[0])) << endl;

    system("pause");
    return 0;
}

2. QT

1.LineEdit

1. Enter the password

this->ui->lineEdit->setEchoMode(QLineEdit::Password);

2. Smart Tips

    //可以设置匹配模式
    QStringList list;
    list << "1" << "12" << "123"<< "1234"<< "12345";
    QCompleter * completer = new QCompleter(list,this);
    this->ui->lineEdit->setCompleter(completer);

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2. Control movement

//动态移动
setGeometry(30,30,3,0)

3. Start the program

QProcess *myProcess = new QProcess();
//获取到输入框输入的内容启动，类似cmd
myProcess->start(this->ui->cmd_line->text().trimmed());

4.Notepad

Tips accumulated recently in notepad

1. Open the file

void MainWindow::on_action_O_triggered()
{
    //打开窗口获取到文件绝对路径
    QString filePath = QFileDialog::getOpenFileName(this,"Open File",QDir::currentPath());
    if(!filePath.isEmpty())
    {
        //裁剪路径
        QStringList list = filePath.split("/");
        //设置标题
        this->setWindowTitle(list[list.length() - 1]);
        QFile * file = new QFile;
        file->setFileName(filePath);
        bool isOpen = file->open(QIODevice::ReadOnly);
        if(isOpen)
        {
            QTextStream in(file);
            QString text = in.readAll();
            this->ui->textEdit->setText(text);
            file->close();
            delete file;
        }
    }
}

This code is similar to the [Open] function of Notepad

2. Fonts

//字体
void MainWindow::on_menu_font_triggered()
{
    //获取选中的字体
    bool ok;
    QFont font = QFontDialog::getFont(&ok,this);
    if(ok)
    {
        this->ui->textEdit->setFont(font);
    }
}

3. Color

//设置字体颜色
void MainWindow::on_menu_color_triggered()
{
    QColor color = QColorDialog::getColor(Qt::black, this);
    if(color.isValid())
    {
        this->ui->textEdit->setTextColor(color);
    }
}

4. Time

//时间
void MainWindow::on_menu_time_triggered()
{
    QDateTime dataTime = QDateTime::currentDateTime();
    QString time= dataTime.toString("yyyy-MM-dd HH:mm:ss");
    this->ui->textEdit->append(time);
}

5. Open the website

    //打开网页
    QDesktopServices::openUrl(QUrl("https://www.baidu.com/"));

I will update the rest from time to time