QWidget::setLayout: 试图设置 QLayout ""在 Widget“"上，它已经有一个布局

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

我正在尝试通过代码(不是在 Designer 中)手动设置小部件的布局，但我做错了，因为我收到了以下警告:

I'm trying to set the layout of a widget manually through code (not in Designer), but I'm doing something wrong, because I get this warning:

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

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

而且布局也很乱(标签在顶部，而不是底部).

And also the layout is messed up (the label is at the top, instead of the bottom).

这是重现问题的示例代码:

This is an example code that reproduces the problem:

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    QLabel *label = new QLabel("Test", this);
    QHBoxLayout *hlayout = new QHBoxLayout(this);
    QVBoxLayout *vlayout = new QVBoxLayout(this);
    QSpacerItem *spacer = new QSpacerItem(40, 20, QSizePolicy::Fixed);
    QLineEdit *lineEdit = new QLineEdit(this);
    hlayout->addItem(spacer);
    hlayout->addWidget(lineEdit);
    vlayout->addLayout(hlayout);
    vlayout->addWidget(label);
    setLayout(vlayout);
}

推荐答案

所以我相信你的问题出在这一行:

So I believe your problem is in this line:

QHBoxLayout *hlayout = new QHBoxLayout(this);

特别是，我认为问题在于将 this 传递到 QHBoxLayout.因为你打算让这个 QHBoxLayout 不是 this 的顶级布局，所以你不应该将 this 传递给构造函数.

In particular, I think the problem is passing this into the QHBoxLayout. Because you intend for this QHBoxLayout to NOT be the top level layout of this, you should not pass this into the constructor.

这是我的重写，我在本地侵入了一个测试应用程序，似乎工作得很好:

Here's my re-write that I hacked into a test app locally and seems to work great:

Widget::Widget(QWidget *parent) :
    QWidget(parent)
{
    QLabel *label = new QLabel("Test");
    QHBoxLayout *hlayout = new QHBoxLayout();
    QVBoxLayout *vlayout = new QVBoxLayout();
    QSpacerItem *spacer = new QSpacerItem(40, 20, QSizePolicy::Fixed);
    QLineEdit *lineEdit = new QLineEdit();
    hlayout->addItem(spacer);
    hlayout->addWidget(lineEdit);
    vlayout->addLayout(hlayout);
    vlayout->addWidget(label);
    setLayout(vlayout);
}

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