无法从MainWindow在QGridLayout中显示小部件 [英] Not able to display widgets in QGridLayout from MainWindow

问题描述

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    reminderTextEdit     = new QTextEdit("");
    reminderTextEdit->setPlaceholderText("What do you want to be reminded of?");
    /// Setting parent is necessary otherwise it will be created in a window of its own.
    reminderTextEdit->setParent(this);
    reminderTextEdit->show();

    dateComboBox         = new QComboBox();
    dateComboBox->setParent(this);
    dateComboBox->show();

    monthComboBox        = new QComboBox();
    monthComboBox->setParent(this);
    monthComboBox->show();

    yearComboBox         = new QComboBox();
    yearComboBox->setParent(this);
    yearComboBox->show();

    doneAndAddMoreButton = new QPushButton();
    doneAndAddMoreButton->setParent(this);
    doneAndAddMoreButton->show();

    doneAndQuitButton    = new QPushButton();
    doneAndQuitButton->setParent(this);
    doneAndQuitButton->show();

    gridLayout           = new QGridLayout;
    gridLayout->addWidget(reminderTextEdit, 0, 0, 0, 0);
    gridLayout->addWidget(dateComboBox, 1, 0);
    gridLayout->addWidget(monthComboBox, 1, 1);
    gridLayout->addWidget(yearComboBox, 1, 2);
    gridLayout->addWidget(doneAndAddMoreButton, 2, 0);
    gridLayout->addWidget(doneAndQuitButton, 2, 1);
}

此代码仅在其中生成一个父窗口和一个子窗口.

This code just produces a parent window and a child window in it.

在末尾添加setLayout(gridLayout);会产生以下错误:

Adding setLayout(gridLayout); at the end of it produces following error:

QWidget::setLayout: Attempting to set QLayout "" on MainWindow "", which already has a layout

请指出错误的做法.

推荐答案

QMainWindow已经具有固定的布局.因此，您不能重新分配一个.参见此处: http://doc.qt.io/qt-5/qmainwindow. html#details

QMainWindow has already a fixed layout. So you cannot reassign one. See here: http://doc.qt.io/qt-5/qmainwindow.html#details

QMainWindow具有自己的布局，您可以在其中添加QToolBars， QDockWidgets，QMenuBar和QStatusBar.布局有一个中心 可以被任何类型的小部件占据的区域.

QMainWindow has its own layout to which you can add QToolBars, QDockWidgets, a QMenuBar, and a QStatusBar. The layout has a center area that can be occupied by any kind of widget.

您可以做的是将空"窗口小部件设置为中央窗口小部件并为其提供布局.

What you can do is set an "empty" widget as central widget and give it the layout.

QWidget *centralWidget = new QWidget(); //set parent to this
//...
reminderTextEdit = new QTextEdit("");
reminderTextEdit->setPlaceholderText("What do you want to be reminded of?");
//...

centralWidget->setLayout(gridLayout);    
setCentralWidget(window);

正如@thuga在评论中提到的:将小部件添加到布局中时，它将承担该项目的责任(使它们成为父项).因此，当您将项目添加到布局时，您不需要首先声明一个父项.

As @thuga mentioned in the comments: when you add a widget to the layout it will take the responsibility of the item (reparent them). So when you add the items to the layout you don't need to declare a parent in the first place.

您提供给setCentralWidget

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