04 qt功能类、对话框类和文件操作

 [static] QTime QTime::currentTime()  //获取当前的系统时间，就是此时的时间，不会自动往下走

QTime(int h, int m, int s = 0, int ms = 0)

QTime time(0,0,0); //可以做为秒表的功能
再通过增加毫秒的时间，增加到1000，秒针就会自动加1

ui->dateLabel->setText(QDate::currentDate().toString("yyyy-MM-dd"));
   qDebug() << QDate::currentDate().year(); // 获得当前的年份
   qDebug() << QDate::currentDate().month(); // 获得当前的月数
   qDebug() << QDate::currentDate().dayOfWeek(); //这周的第几天

[static] QColor QColorDialog::getColor(const QColor &initial = Qt::white,
 QWidget *parent = nullptr, const QString &title = QString(),
 QColorDialog::ColorDialogOptions options = ColorDialogOptions())

void ColorWindow::on_colorSetButton_clicked()
{
//[1]打开颜色对话框，并选择一个颜色
    QColor color =   QColorDialog::getColor();
//[2] 将颜色值分别获取它的rgb
    int red = color.red();
    int green = color.green();
    int blue = color.blue();
//[3] 将rgb设置给控件
    ui->testLabel->setStyleSheet(QString("background-color: rgb(%1, %2, %3);").arg(red)
                                 .arg(green)
                                 .arg(blue));
}

[static] QFont QFontDialog::getFont(bool *ok, const QFont &initial,
 QWidget *parent = nullptr, const QString &title = QString(),
 QFontDialog::FontDialogOptions options = FontDialogOptions())

bool ok;
  QFont font = QFontDialog::getFont(&ok, QFont("Times", 12), this);
  if (ok) {
      // font is set to the font the user selected
  } else {
      // the user canceled the dialog; font is set to the initial
      // value, in this case Times, 12.
  }

void FontDialogWin::on_fontSetButton_clicked()
{
       //[1] 打开对话框
    bool ok;
      QFont font =  QFontDialog::getFont(&ok,this);
      if(ok)
      {
          qDebug() << "ok = " << ok << font.toString();
          //[2] 如果获得成功，则将font设置给指定的控件
          ui->label->setFont(font);
      }else {
          qDebug() << " get font failed";
      }

}

（The QFileDialog class provides a dialog that allow users to select files or directories）

QString fileName = 
QFileDialog::getOpenFileName(this, tr("Open File"),/*tr()---国标化标准*/
                         "/home", //绝对路径
                   tr("Images (*.png *.xpm *.jpg)"));

"Images (*.png *.xpm *.jpg);;Text files (*.txt);;XML files (*.xml)"

void FileDialogWin::on_browseButton_clicked()
{
    //[1]打开文件对话框
     QString filePath =  QFileDialog::getOpenFileName(this,"打开文件",
          "D:/Qt/qt_gz2057_workspace/DAY4/cpp_demo6_qfiledialog",
          "Text files (*.cpp *.h)");
     //[2] 将文件路径更新UI
     ui->fileEdit->setText(filePath);

   //[3]根据文件路径打开此文件

}

QFile(const QString &name)
QFile()和void setFileName(const QString &name)

bool open(QIODevice::OpenMode mode) override

QByteArray QIODevice::readAll()  ----> 一次性读取文件中所有的数据，数据以
QByteArray（字节数组）

void FileDialogWin::on_browseButton_clicked()
{
    //[1]打开文件对话框
     QString filePath =  QFileDialog::getOpenFileName(this,"打开文件",
                    "D:/Qt/qt_gz2057_workspace/DAY4/cpp_demo6_qfiledialog",
                    "Text files (*.cpp *.h)");
     //[2] 将文件路径更新UI
     ui->fileEdit->setText(filePath);

   //[3]根据文件路径打开此文件
    QFile file(filePath);

  //[4] 打开文件 --- open
    if(file.open(QIODevice::ReadOnly))
    {
        QByteArray array =  file.readAll();
        qDebug() << "ARRAY= " << array;
    }

   file.close();
}

 void SaveFileWin::on_saveButton_clicked()
{
      //[1] 打开另存为对话框,并手动设置文件的名字
    QString filename = QFileDialog::getSaveFileName(this);

    //[2] 创建文件和打开文件
    QFile file(filename);

    if(file.open(QIODevice::WriteOnly))
    {
        //[3] 获得UI控件上的内容，再将它写入到文件中
        QString data = ui->textEdit->toPlainText();
         //QString ----> QByteArray ----  QString::toUtf8() const : QByteArray
        file.write(data.toUtf8());
    }
    file.close();
}