QT 5.11

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在visual studio 2017中配置Qt

QT creator編程C++第一步，説“Hello world!”

QLabel label("Hello, world");
label.setGeometry(200,200,200,200);
label.show();

Qt主窗口(Top Level Window)

QtGuiApplication1 w;           //創造一個主窗口物件
w.resize(300, 300);      //窗口尺寸為300*300
w.move(100, 100);        //窗口移動到距螢幕左上角100*100處
int windowXPos = w.x(); //窗口左上角x座標
int windowYPos = w.y(); //窗口左上角y座標
QRect windowGeometry = w.frameGeometry(); //返回的QRect可得窗口長、寬、位置等資訊。   
w.setWindowTitle(QObject::tr("Window Title")); //設定窗口標題
w.show();               //在螢幕上秀出窗口

元件概念(QWidget)

MainWindow, Dialog, Label, Buttons inherits from QWidget inherits from QObject.
Top Level Widget includes MainWindow that must has no parents.
Non-window widget includes labels, buttons that must has a parent.
Typically top level widget put in stack in main() but sub widget put in heap using new with chained parents.

int main(int argc, char *argv[]) {
QApplication a(argc, argv);
QLabel *label1 = new QLabel();
label1->setText("Label 1");
label1->show();
QLabel label2;
label2.setText("Label 2");
label2.show();
int ret = a.exec();
delete label1;    //label1需自行釋放記憶體
return ret;
}

QWidget (Typical)

int main(int argc, char *argv[]) {
QApplication a(argc, argv);
QWidget w;
w.show();
return a.exec();
}

QPushButton

class MyWidget : public QWidget
{
 Q_OBJECT
public:
 MyWidget(QWidget *parent = 0) {
  setWindowTitle(tr("My Title"));
  btn1 = new QPushButton(tr("Start"), this); //第二個參數指定父元件，如果沒有就要用布局管理員，否則無法顯現該元件
  btn1->setGeometry(30, 30, 80, 30);         //設定位置大小
  btn1->setText(tr("Change"));               //設定內容文字
  btn1->setFont(QFont("Times", 12));       //設定字型
  btn2 = new QPushButton(this);
  btn2->setGeometry(30, 80, 60, 60);
  btn2->setIcon(QIcon("icon.jpg"));       //設定按鈕圖案
  btn2->setIconSize(QSize(50, 50));       //設定圖案大小
 }
private:
 QPushButton *btn1;
 QPushButton *btn2;
};

#include "MyWidget.h"
int main(int argc, char *argv[]) {
QApplication a(argc, argv);
MyWidget w;
w.show();
return a.exec();
}

QLabel

MyWidget(QWidget *parent = 0) {
 setWindowTitle(tr("Two Labels"));
 label1 = new QLabel(this);
 label1->setText(tr("Text Label"));
 label1->setGeometry(20, 20, 60, 20);        //設定位置大小
 label1->setAlignment(Qt::AlignCenter);   //label文字置中

 QPixmap p("icon.png");                   //載入圖檔
 label2 = new QLabel(this);
 label2->setGeometry(25, 60, 60, 60);
 label2->setPixmap(p.scaled(60, 60, Qt::KeepAspectRatio));  //將圖案縮小為(60,60)
}

QFrame

MyWidget(QWidget *parent = 0) {
 setWindowTitle(tr("QFrame Title"));
 myFrame = new QFrame(this);
 myFrame->setGeometry(10, 10, 150, 40);
 myFrame->setLineWidth(2);
 myFrame->setFrameStyle(QFrame::Box | QFrame::Sunken);
}

QRadioButton

setWindowTitle(tr("Radio Titles"));
myGroupBox = new QGroupBox(tr("Set of buttons"), this);
myGroupBox->setGeometry(30, 30, 100, 100);
check1 = new QRadioButton(tr("B1"), this);
check1->setChecked(true);                //設定check1為打勾狀態
check2 = new QRadioButton(tr("B2"), this);
check3 = new QRadioButton(tr("B3"), this);
myLayout = new QVBoxLayout;
myLayout->addWidget(check1);
myLayout->addWidget(check2);
myLayout->addWidget(check3);
myGroupBox->setLayout(myLayout);

And more widght...


信號槽範例

Button clicked() broadcasts a signal and a "private slot:" function can handle data.

connect(myBtn, SIGNAL(clicked()), this, SLOT(showMessageBox()));
connect(myEdit, SIGNAL(textChanged()), this, SLOT(showMessageBox()));

The object button broadcasts a signal clicked() and this object handle it by the slot function.

class MyWidget : public QWidget
{
 Q_OBJECT
public:
 MyWidget(QWidget *parent = 0) :
  QWidget(parent)
 {
  m_value = 0;
  myLcd = new QLCDNumber(this);
  myLcd->setGeometry(80, 30, 150, 50);
  mySlider = new QSlider(Qt::Horizontal, this);
  mySlider->setRange(0, 100);
  mySlider->setValue(30);
  mySlider->setGeometry(80, 110, 150, 50);
  connect(mySlider, SIGNAL(valueChanged(int)), this, SLOT(setValue(int)));
  connect(this, SIGNAL(valueChanged(int)), myLcd, SLOT(display(int)));
  setValue(30);
 }
private:
 int m_value;
 QLCDNumber *myLcd;
 QSlider *mySlider;
public slots:
 void setValue(int value) {
  if (value != m_value) {
   m_value = value;
   emit valueChanged(m_value);
  }
 }
signals:
 void valueChanged(int);
};

自建的signal和slot函式回傳值皆為void，且參數基本上要相同(本例為int)
若signal的參數多於slot的參數，則額外的參數會被slot忽略


QTableWidget

















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