4.layout

/* 应用程序抽象类 */
#include <QApplication>

/*窗口类*/
#include <QWidget>

#include <QLabel>

/* 按钮 */
#include <QPushButton>
#include <QLineEdit>

#include <QVBoxLayout>
#include <QHBoxLayout>

#include <QGridLayout>

int main(int argc, char* argv[])
{
    QApplication app(argc, argv);

    /* 构造一个窗口*/
    QWidget w;
#if 0
    /* 按钮也是个窗口 */
    QPushButton button;
    button.setText("Button");
    /* 窗口对象的父子关系，影响显示位置 */
    /* 没有父窗口的窗口，我们称之为主窗口 */
 //   button.setParent(&w);
    button.show();

    QLineEdit edit;
    edit.setParent(&w);


    QHBoxLayout layout;
    layout.addStretch(1);
    layout.addWidget(&button, 1);
    layout.addSpacing(50);
    layout.addWidget(&edit, 1);
    layout.addStretch(1);
#endif

#if 0
    QGridLayout layout;
    layout.setColumnStretch(3, 1);
    layout.setRowStretch(4, 1);
    layout.setColumnStretch(0, 1);
    layout.setRowStretch(0, 1);

    layout.addWidget(&button, 1, 1);
    layout.addWidget(&edit, 1, 2);
    layout.addWidget(new QPushButton("1, 0"), 2, 1);
    layout.addWidget(new QPushButton("1, 1"), 2, 2);

    layout.addWidget(new QPushButton("aaa"), 3, 1, 1, 2);
#endif

    QGridLayout layout;
    QLineEdit* password;
    layout.setColumnStretch(3, 1);
    layout.setRowStretch(4, 1);
    layout.setColumnStretch(0, 1);
    layout.setRowStretch(0, 1);

    layout.addWidget(new QLabel("Username:"), 1, 1);
    layout.addWidget(new QLineEdit(), 1, 2);
    layout.addWidget(new QLabel("Password:"), 2, 1);
    layout.addWidget(password = new QLineEdit(), 2, 2);

    QHBoxLayout* hBox;
    layout.addLayout(hBox = new QHBoxLayout, 3, 2);
    hBox->addStretch(1);
    hBox->addWidget(new QPushButton("Login"));

   // layout.addWidget(new QPushButton("登录"), 3, 2);

    password->setEchoMode(QLineEdit::Password);





    /*显示窗口*/
    w.show();
    w.setLayout(&layout);




    /* QT对C++的拓展 */
    // std::bind std::function
//    QObject::connect(&button, SIGNAL(clicked()), &w, SLOT(close()));

    w.setWindowTitle("Hello World");

    /*在exec中有一个消息循环*/
    return app.exec();
}