QT learning 22 layout manager (I)

Qt Study 22 Layout manager （ One ）

The problem is

• current GUI The development way ： Absolute positioning

  • Directly in Pixel level Specify the Location and size

    void QWidget::move(int x, int y)

    void QWidget::resize(int x, int y)

• problem ：

  • Location and size of components Unable to adapt to changes in the parent window

Layout manager

• Solution ： Layout manager
  • Provide related classes Manage the layout of interface components
    • can Auto arrange Interface components in the window
    • After the window changes Automatically update the size of components
• QLayout yes Qt in Abstract base class of layout manager
• By inheritance QLayout Realized Different and complementary functions The layout manager for
• Qt Medium can Customize... As needed Layout manager
• Layout manager Not interface components , But the positioning strategy of interface components

• QBoxLayout Layout manager
  • With level perhaps vertical Manage interface components in a way

• The layout manager can Nesting with each other , Form a more complex layout
  • Layout nesting Almost all commonly used interface layouts can be completed
  • Custom layout classes can achieve Personalized interface layout The effect of
• QBoxLayout Nested instances

Code experiments

#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();
    void testVBoxLayout();
    void testHBoxLayout();
    void testVHBoxLayout();
public:
    Widget(QWidget *parent = 0);
    ~Widget();
};

#endif // WIDGET_H

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


Widget::Widget(QWidget *parent) : QWidget(parent),
    TestBtn1(this), TestBtn2(this), TestBtn3(this), TestBtn4(this)
{
    
    initBtn();			//  Initialize button control 
    //initControl(); //  Absolute positioning , Unable to adapt window changes 
    //testVBoxLayout(); //  Vertical layout management 
    //testHBoxLayout(); //  Horizontal layout management 
    testVHBoxLayout();    //  Nested layout management 
}

Widget::~Widget()
{
    

}

void Widget::initBtn()
{
    
    TestBtn1.setText("Test Button 1");
    TestBtn2.setText("Test Button 2");
    TestBtn3.setText("Test Button 3");
    TestBtn4.setText("Test Button 4");
    //  Set the minimum size of the button 
    TestBtn1.setMinimumSize(160, 30);
    TestBtn2.setMinimumSize(160, 30);
    TestBtn3.setMinimumSize(160, 30);
    TestBtn4.setMinimumSize(160, 30);
    //  Set button size policy 
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
}

void Widget::initControl()
{
    
    TestBtn1.setText("Test Button 1");
    TestBtn1.move(20, 20);
    TestBtn1.resize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.move(20, 70);
    TestBtn2.resize(160, 30);

    TestBtn3.setText("Test Button 3");
    TestBtn3.move(20, 120);
    TestBtn3.resize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.move(20, 170);
    TestBtn4.resize(160, 30);
}

void Widget::testVBoxLayout()
{
    
    QVBoxLayout* layout = new QVBoxLayout();

    //  Add window controls to layout manager 
    layout->addWidget(&TestBtn1);
    layout->addWidget(&TestBtn2);
    layout->addWidget(&TestBtn3);
    layout->addWidget(&TestBtn4);
    //  Layout manager sets the spacing between controls 
    layout->setSpacing(20);
    //  Set the layout manager of the current window 
    setLayout(layout);
}

void Widget::testHBoxLayout()
{
    
    QHBoxLayout* layout = new QHBoxLayout();
    //  Add window controls to layout manager 
    layout->addWidget(&TestBtn1);
    layout->addWidget(&TestBtn2);
    layout->addWidget(&TestBtn3);
    layout->addWidget(&TestBtn4);
    //  Layout manager sets the spacing between controls 
    layout->setSpacing(20);
    //  Set the layout manager of the current window 
    setLayout(layout);
}

void Widget::testVHBoxLayout()
{
    
    QHBoxLayout* hLayout1 = new QHBoxLayout();
    QHBoxLayout* hLayout2 = new QHBoxLayout();
    QVBoxLayout* vLayout = new QVBoxLayout();

    hLayout1->addWidget(&TestBtn1);
    hLayout1->addWidget(&TestBtn2);
    hLayout1->setSpacing(20);
    hLayout2->addWidget(&TestBtn3);
    hLayout2->addWidget(&TestBtn4);
    hLayout2->setSpacing(20);
    vLayout->addLayout(hLayout1);
    vLayout->addLayout(hLayout2);
    vLayout->setSpacing(20);
    setLayout(vLayout);
}

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

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

    return a.exec();
}

Summary

• Absolute positioning Layout method Not adaptive Window changes
• Qt Provides related classes Manage the layout of interface components
• Qt Predefined Different and complementary functions The layout manager for
• The layout manager can Nested with each other to form a complex layout