QT learning 25 layout manager (4)

Qt Study 25 Layout manager （ Four ）

The most special layout manager

• Trestle layout manager （ QStackedLayout ）
  • All components in Perpendicular to the screen Managed in the direction of
  • Every time There's only one component It will be displayed on the screen
  • Only The topmost component Will be finally displayed

• Characteristics of the trestle layout manager
  • Consistent component size And fill the display area of the parent component
  • Cannot nest directly Other layout managers
  • can Free to switch Components to be displayed
  • Can and can only Show a component
• QStackedLayout Usage Summary of
  • int addWidget(QWidget* widget)
  • QWidget* currentWidget()
  • void setCurrentIndex(int index)
  • int currentIndex()

Programming experiment - Discussion on trestle layout

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QPushButton>

class Widget : public QWidget
{
    
    Q_OBJECT
private:
    QPushButton TestBtn1;
    QPushButton TestBtn2;
    QPushButton TestBtn3;
    QPushButton TestBtn4;
    void initBtn();
    void initControl();
public:
    Widget(QWidget *parent = 0);
    ~Widget();
};

#endif // WIDGET_H

#include "Widget.h"
#include <QStackedLayout>
#include <QHBoxLayout>

Widget::Widget(QWidget *parent) : QWidget(parent),
    TestBtn1(this), TestBtn4(this)
{
    
    initBtn();
    initControl();
}

Widget::~Widget()
{
    

}

void Widget::initBtn()
{
    
    TestBtn1.setText("1st Button");
    TestBtn2.setText("2rd Button");
    TestBtn3.setText("3th Button");
    TestBtn4.setText("Test Button 4: D.T.Software");
}

void Widget::initControl()
{
    
    //  Trestle layout manager 
    QStackedLayout* sLayout = new QStackedLayout();
    sLayout->addWidget(&TestBtn1);

    //  Because the trestle layout manager cannot directly nest other layout managers , So use QWidget Make the middle layer 
    QWidget* w = new QWidget();
    //  stay QWidget Set the horizontal layout manager in 
    QHBoxLayout* hLayout = new QHBoxLayout();
    hLayout->addWidget(&TestBtn2);
    hLayout->addWidget(&TestBtn3);
    w->setLayout(hLayout);
    //  And then QWidget Add to the trestle layout manager , Play the effect of indirectly nesting the horizontal layout manager 
    sLayout->addWidget(w);

    sLayout->addWidget(&TestBtn4);
    sLayout->setCurrentIndex(2);    //0:Btn1, 1:Btn2、Btn3, 2:Btn4
    setLayout(sLayout);
}

#include "Widget.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    
    QApplication a(argc, argv);
    Widget w;
    w.show();

    return a.exec();
}

The concept of timer

• The timer is In engineering development A very important role
• Timer for Every certain event triggers a message
• timer news It will eventually be transformed into Function call
• On the macro
  • The timer will call the specified function at each event interval

Qt The timer in

• timer （ QTimer ） How to use

  1. Write timer message processing function

  2. Create a timer object in the program

  3. Connect timer message and message processing function

  4. Set the timer interval and start timing

Programming experiment - Use of timer

The new content ：

#ifndef WIDGET_H
#define WIDGET_H

class Widget : public QWidget
{
    
private slots:
    void timerTimeout();
};

#endif // WIDGET_H

#include <QTimer>

void Widget::initControl()
{
    
    //  The content of the last experiment 
	//  Timer add content 
    QTimer* timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(timerTimeout()));
    timer->start(2000);
}

void Widget::timerTimeout()
{
    
    // layout() Get the layout manager of the current window 
    QStackedLayout* sLayout = dynamic_cast<QStackedLayout*>(layout());
    if (sLayout != NULL) {
    
        int index = (sLayout->currentIndex()+1) % sLayout->count();
        sLayout->setCurrentIndex(index);
    }
}

Summary

• QStackedLayout Manage interface components in a stack
• QStackedLayout Components in At most, there is only one display
• QStackedLayout Sure Free to switch Components to be displayed
• QTimer yes Qt Timer component in
• QTimer The message can be triggered at a specified time interval