Qt代码实现上下左右布局

//实现在上下左右四个方向分别放置按钮
#include 

#include "arrowpad.h"

ArrowPad::ArrowPad(QWidget *parent)
    : QWidget(parent)
{

    upButton = new QPushButton(tr("&Up"));

    downButton = new QPushButton(tr("&Down"));

    leftButton = new QPushButton(tr("&Left"));

    rightButton = new QPushButton(tr("&Right"));


    QGridLayout *mainLayout = new QGridLayout;
    mainLayout->addWidget(upButton, 0, 1);
    mainLayout->addWidget(leftButton, 1, 0);
    mainLayout->addWidget(rightButton, 1, 2);
    mainLayout->addWidget(downButton, 2, 1);
    setLayout(mainLayout);
}