从代码访问在 UI 中创建的 Qt 布局?

2022-01-18 00:00:00 qt widget qt-creator layout c++

这可能是我遇到过的最愚蠢的问题，但我非常困惑.我正在尝试开始使用布局，但由于某种原因无法弄清楚这一点.

This is probably the dumbest problem I have ever had, but I am extremely confused. I am trying to get started with layouts, but for some reason cannot figure this one out.

我尝试通过 .ui 文件添加 QGridLayout，只需将其拖放到我的项目中即可.由于我想在加载时使用小部件填充网格，因此我尝试在调用 this->setupui() 之前/之后使用mainwindow.h"文件中的gridLayout"对象.

I have tried adding a QGridLayout via the .ui file by just drag dropping it into my project. As I want to populate the grid with widgets upon loading, I have tried to use the "gridLayout" object in the "mainwindow.h" file both before/after the this->setupui() is called.

由于我无法弄清楚，我选择尝试使用代码从头开始创建它，并将以下内容添加到 main.cpp 文件中.这也没有显示，所以我想知道如何在表单加载时填充网格.

As I couldn't figure that out, I opted to just try creating it from scratch using code, and added the following to the main.cpp file instead. This did not display either, so I am wondering how on earth I can populate the grid when the form loads.

#include <QtGui/QApplication>
#include <QtGui>
#include "mainwindow.h"

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

    QGridLayout *grid = new QGridLayout;

    QLabel *label1 = new QLabel("test");
    QLabel *label2 = new QLabel("test 2");

    grid->addWidget(label1, 0, 0);
    grid->addWidget(label2, 0, 1);
    w.setLayout(grid);

    w.show();
    return app.exec();
}

推荐答案

假设你已经简单地将 QtDesigner 中的 QGridLayout 设置为 MainWindow 中的 centralWidget，如下所示:

Assuming, you have simply set a QGridLayout in QtDesigner to your centralWidget in the MainWindow like this:

您可以在 MainWindow 代码中使用正确的对象名称访问它(这里是 gridLayout):

you can access it in your MainWindow code in that way with the correct object name (here it is gridLayout):

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->gridLayout->addWidget(new QLabel("hello world"),0,0);
}

如果您在 QtDesigner 或代码中设置了布局并且想要更改布局，QWidget 不会让您安装另一个布局，您将收到如下错误消息:

If you have set a layout in QtDesigner or in code and you want to change the layout, QWidget won't let you install another one and you will get an error message like this:

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

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

在这种情况下，您必须首先删除现有布局，然后像上面的代码一样安装新布局.

In this case you have to delete the existing layout at first and then install the new one like in your code above.

如果你想在你的主函数中访问布局，你可以通过 QObject::findChild 函数来实现，如下所示:

If you want to access the layout in your main function you can achieve this by the QObject::findChild function like this:

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;

    QGridLayout *gridLayout = w.findChild<QGridLayout*>("gridLayout");
    Q_ASSERT(gridLayout);
    gridLayout->addWidget(new QLabel("hello, the second"));

    w.show();
    return a.exec();
}

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