QT常见布局器使用

布局简介

为什么要布局？通过布局拖动不影响鼠标拖动窗口的效果等优点.QT设计器布局比较固定，不方便后期修改和维护；在Qt里面布局分为四个大类：

盒子布局：QBoxLayout

网格布局：QGridLayout

表单布局：QFormLayout

抽屉布局：QStackedLayout

QBoxLayout

一般使用它的两个子类QHBoxLayout 和 QVBoxLayout 负责水平和垂直布局

垂直布局示例：

#include "mainwindow.h"
#include <QApplication>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QWidget* w=new QWidget;
    setCentralWidget(w);//注意MainWindow不能直接进行布局

    QVBoxLayout* vlayout=new QVBoxLayout;
    QPushButton* b1=new QPushButton("b1");
    QPushButton* b2=new QPushButton("b2");
    QPushButton* b3=new QPushButton("b3");

    vlayout->addWidget(b1);
    vlayout->addStretch(1);//增加一个伸缩量
    vlayout->addWidget(b2);
    vlayout->addStretch(1);//增加一个伸缩量
    vlayout->addWidget(b3);
    vlayout->addStretch(2);//增加一个伸缩量

    centralWidget()->setLayout(vlayout);
    this->resize(300, 300);
}

水平布局示例：

#include "mainwindow.h"
#include <QApplication>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    this->setWindowTitle("水平布局");
    QWidget* w=new QWidget;
    setCentralWidget(w);

    QHBoxLayout* hlayout=new QHBoxLayout;
    QPushButton* b1=new QPushButton("b1");
    QPushButton* b2=new QPushButton("b2");
    QPushButton* b3=new QPushButton("b3");

    hlayout->addWidget(b1);
    hlayout->addStretch(1);//增加一个伸缩量
    hlayout->addWidget(b2);
    hlayout->addStretch(1);//增加一个伸缩量
    hlayout->addWidget(b3);
    hlayout->addStretch(2);//增加一个伸缩量

    centralWidget()->setLayout(hlayout);
    this->resize(300, 300);
}

水平布局和垂直布局综合（可以结合QGroupBox容器进行布局）：

#include "mainwindow.h"
#include <QApplication>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QGroupBox>
#include <QRadioButton>
MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    this->setWindowTitle("垂直布局");
    QWidget* w=new QWidget;
    setCentralWidget(w);

    QVBoxLayout* container=new QVBoxLayout;

    QGroupBox *hobby_box = new QGroupBox("爱好");
    QVBoxLayout* v_layout=new QVBoxLayout;
    QRadioButton* btn1 = new QRadioButton("抽烟");
    QRadioButton* btn2 = new QRadioButton("喝酒");
    QRadioButton* btn3 = new QRadioButton("玩乐");
    v_layout->addWidget(btn1);
    v_layout->addWidget(btn2);
    v_layout->addWidget(btn3);
    hobby_box->setLayout(v_layout);

    QGroupBox* gender_box = new QGroupBox("性别");
    QHBoxLayout* h_layout = new QHBoxLayout();
    QRadioButton* btn4 =  new QRadioButton("男");
    QRadioButton* btn5 = new QRadioButton("女");
    h_layout->addWidget(btn4);
    h_layout->addWidget(btn5);
    gender_box->setLayout(h_layout);

    container->addWidget(hobby_box);
    container->addWidget(gender_box);

    centralWidget()->setLayout(container);
    this->resize(300, 300);
}

QGridLayout

网格布局，有的人称之为九宫格布局；示例如下：

#include "mainwindow.h"
#include <QApplication>
#include <QPushButton>
#include <QVBoxLayout>
#include <QHBoxLayout>
#include <QGroupBox>
#include <QRadioButton>
#include <QStringList>
#include <QLineEdit>
#include <QGridLayout>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    this->setWindowTitle("网格布局");
    QWidget* w=new QWidget;
    setCentralWidget(w);

    QVBoxLayout* container=new QVBoxLayout;

    QPushButton* m_buttons[20];
    const char* btnText[20] =
    {
        "7", "8", "9", "+", "(",
        "4", "5", "6", "-", ")",
        "1", "2", "3", "*", "<-",
        "0", ".", "=", "/", "C"
    };

    QLineEdit* edit = new QLineEdit();
    edit->setPlaceholderText("请输入内容");

    QGridLayout* grid = new QGridLayout();

    int line_number = 0;
    int col_number = 0;
    for(line_number = 0;line_number < 4;line_number++){
         // 此时line_number是第几行
        for(col_number = 0;col_number < 5;col_number++){
            // 此时col_number是第几列
            m_buttons[line_number*5 + col_number] = new QPushButton();
            m_buttons[line_number*5 + col_number]->setText(btnText[line_number*5 + col_number]);
            grid->addWidget(m_buttons[line_number*5 + col_number], line_number, col_number);
        }
    }
    container->addWidget(edit);
    container->addLayout(grid);

    centralWidget()->setLayout(container);
    this->resize(300, 300);
}