第22课 - 布局管理器（QBoxLayout和QGridLayout）

1、存在的问题 

课程目前的GUI开发方式：绝对定位 

        －直接在像素级指定各个组件的位置和大小 

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

                        void QWidget::resize (int w, int h) 

问题 

            组件的位置和大小无法自适应父窗口的变化 

 

2、解决方案：布局管理器 

提供相关的类对界面组件进行布局管理

        - 能够自动排列窗口中的界面组件 

        - 窗口变化后自动更新界面组件的大小 

 

QLayout是Qt中布局管理器的抽象基类 

通过继承QLayout实现了功能各异且互补的布局管理器 

Qt中可以根据需要自定义布局管理器 

布局管理器不是界面部件，而是界面部件的定位策略 

 

3、QBoxLayout布局管理器 

－以水平（horizontal）或者垂直（vertical）的方式管理界面组件 

                

 

4、布局管理器

布局管理器可以相互嵌套，形成更加复杂的布局方式

      －布局嵌套几乎可以完成所有常用的界面布局 

     －自定义布局类可以达到个性化界面布局的效果 

QBoxLayout嵌套实例 

5、编程实验 

QBoxLayout、布局嵌套实例 22-1.pro 

Widget.h

#ifndef _WIDGET_H_
#define _WIDGET_H_

#include <QtGui/QWidget>
#include <QPushButton>

class Widget : public QWidget
{
    Q_OBJECT
private:
    QPushButton TestBtn1;
    QPushButton TestBtn2;
    QPushButton TestBtn3;
    QPushButton TestBtn4;

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

#endif

Widget.cpp

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


Widget::Widget(QWidget *parent) : QWidget(parent),
    TestBtn1(this), TestBtn2(this), TestBtn3(this), TestBtn4(this)
{
    //initControl();
    //testVBoxLayout();
    //testHBoxLayout();
    //testVHBoxLayout();
}

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

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    hLayout1->setSpacing(10);
    hLayout1->addWidget(&TestBtn1);
    hLayout1->addWidget(&TestBtn2);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    hLayout2->setSpacing(10);
    hLayout2->addWidget(&TestBtn3);
    hLayout2->addWidget(&TestBtn4);

    vLayout->setSpacing(10);
    vLayout->addLayout(hLayout1);
    vLayout->addLayout(hLayout2);

    setLayout(vLayout);
}

void Widget::testHBoxLayout()
{
    QHBoxLayout* layout = new QHBoxLayout();

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    layout->setSpacing(30);
    layout->addWidget(&TestBtn1);
    layout->addWidget(&TestBtn2);
    layout->addWidget(&TestBtn3);
    layout->addWidget(&TestBtn4);

    setLayout(layout);
}

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

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    layout->setSpacing(30);
    layout->addWidget(&TestBtn1);
    layout->addWidget(&TestBtn2);
    layout->addWidget(&TestBtn3);
    layout->addWidget(&TestBtn4);

    setLayout(layout);
}

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);
}

Widget::~Widget()
{
    
}

6、布局管理器 

布局管理器中的比例系数 

        －默认情况下以等比例的方式更新组件的大小

        －可以自定义组件大小更新时的比例系数 

QBoxlayout中的比例系数设置 

         - void setStretch(int index, int stretch)   //index 格子下标，

         - bool setStretchFactor(QWidget* widget, int stretch)  //具体组件的比例系数

         - bool setStretchFactor(QLayout* layout, int stretch)  //布局管理器管理另一个布局管理器

7、编程实验 

比例系数初探    Widget.cpp

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


Widget::Widget(QWidget *parent) : QWidget(parent),
    TestBtn1(this), TestBtn2(this), TestBtn3(this), TestBtn4(this)
{
    //initControl();
    //testVBoxLayout();
    //testHBoxLayout();
    //testVHBoxLayout();
}

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

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    hLayout1->setSpacing(10);
    hLayout1->addWidget(&TestBtn1);
    hLayout1->addWidget(&TestBtn2);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    hLayout2->setSpacing(10);
    hLayout2->addWidget(&TestBtn3);
    hLayout2->addWidget(&TestBtn4);

    vLayout->setSpacing(10);
    vLayout->addLayout(hLayout1);
    vLayout->addLayout(hLayout2);
    vLayout->setStretchFactor(hLayout1, 1);
    vLayout->setStretchFactor(hLayout2, 3);

    setLayout(vLayout);
}

void Widget::testHBoxLayout()
{
    QHBoxLayout* layout = new QHBoxLayout();

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    layout->setSpacing(30);
    layout->addWidget(&TestBtn1);
    layout->addWidget(&TestBtn2);
    layout->addWidget(&TestBtn3);
    layout->addWidget(&TestBtn4);
    layout->setStretchFactor(&TestBtn1, 1);
    layout->setStretchFactor(&TestBtn2, 2);
    layout->setStretchFactor(&TestBtn3, 1);
    layout->setStretchFactor(&TestBtn4, 3);

    setLayout(layout);
}

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

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    layout->setSpacing(30);
    layout->addWidget(&TestBtn1);
    layout->addWidget(&TestBtn2);
    layout->addWidget(&TestBtn3);
    layout->addWidget(&TestBtn4);
    layout->setStretch(0, 1);
    layout->setStretch(1, 1);
    layout->setStretch(2, 2);
    layout->setStretch(3, 2);

    setLayout(layout);
}

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);
}

Widget::~Widget()
{
    
}

                    组件的初始大小是独立于布局管理器设置的，因此 

                    不能保证组件的大小始终符合比例系数的设置！ 

 

8、QGridLayout布局管理器 

－以网格（二维）的方式管理界面组件 

QGridLayout中的比例系数设置 

        - void setColumnStretch(int column, int stretch) 

        - void setRowStretch(int row, int stretch) 

9、编程实验 

QGridLayout   23-2.pro 

Widget.cpp

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

Widget::Widget(QWidget *parent) : QWidget(parent),
    TestBtn1(this), TestBtn2(this), TestBtn3(this), TestBtn4(this)
{
    //testGridLayout1();
    //testGridLayout2();
}

void Widget::testGridLayout1()
{
    QGridLayout* layout = new QGridLayout();

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    layout->setSpacing(10);
    layout->addWidget(&TestBtn1, 0, 0);
    layout->addWidget(&TestBtn2, 0, 1);
    layout->addWidget(&TestBtn3, 1, 0);
    layout->addWidget(&TestBtn4, 1, 1);
    layout->setRowStretch(0, 1);//设置比例因子
    layout->setRowStretch(1, 3);
    layout->setColumnStretch(0, 1);
    layout->setColumnStretch(1, 3);

    setLayout(layout);
}

void Widget::testGridLayout2()
{
    QGridLayout* layout = new QGridLayout();

    TestBtn1.setText("Test Button 1");
    TestBtn1.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn1.setMinimumSize(160, 30);

    TestBtn2.setText("Test Button 2");
    TestBtn2.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn2.setMinimumSize(160, 30);

    TestBtn3.setText("Test Button 3");
    TestBtn3.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn3.setMinimumSize(160, 30);

    TestBtn4.setText("Test Button 4");
    TestBtn4.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);
    TestBtn4.setMinimumSize(160, 30);

    layout->setSpacing(10);
    layout->addWidget(&TestBtn1, 0, 0, 2, 1);//放0，0位置，占两行一列
    layout->addWidget(&TestBtn2, 0, 1, 2, 1);
    layout->addWidget(&TestBtn3, 2, 0, 1, 2);
    layout->addWidget(&TestBtn4, 3, 0, 1, 2);

    setLayout(layout);
}

Widget::~Widget()
{
    
}

布局管理器的嵌套 

              - QGridLayout支持嵌套其它布局管理器成为其管理对象 

10、小结 

绝对定位的布局方式无法自适应窗口的变化 

Qt提供了相关的类对界面组件进行布局管理 

Qt预定义了功能各异且互补的布局管理器 

布局管理器能够相互嵌套形成复杂的布局 

 

QGridLayout以网格的方式对组件进行管理 

QGridLayout中的组件可以根据需要跨越多个网格 

QBoxLayout和QGridLayout支持比例系数的概念 

比例系数决定了组件大小的相对变化