Sizepolicy policy in layout management

One 、sizeHint What is the value ？

When each part is dragged and dropped onto the window , There will be a default sizeHint Size value of ( The top-level window returns sizeHint The value is (-1,-1)   ), Same component In the layout manager and Not in manager Of sizeHint It's not the same size , But we found that , Components in the layout pushbutton_1 actual size neither sizeHint The default value of is not set before dragging into the layout size, It's a reference sizeHint The value obtained after ;pushbutton_3 Of size The size is the size we drag in , Not used sizeHint Value

 qDebug()<<"pushButton_1:"<<"sizeHint"<<ui->pushButton_1->sizeHint()<<"size:"<<ui->pushButton_1->size();
    qDebug()<<"pushButton_2:"<<"sizeHint"<<ui->pushButton_2->sizeHint()<<"size:"<<ui->pushButton_2->size();
    qDebug()<<"pushButton_3:"<<"sizeHint"<<ui->pushButton_3->sizeHint()<<"size:"<<ui->pushButton_3->size();

The results are as follows , It can be seen that the dimensions in the layout are only for reference sizeHint Value , Not the same as it ; There is no layout pushbutton__3 Size for us to drag in geometry Property ：

pushButton_1: sizeHint QSize(97, 28) size: QSize(100, 30)
pushButton_2: sizeHint QSize(97, 28) size: QSize(100, 30)
pushButton_3: sizeHint QSize(105, 28) size: QSize(251, 29)

Two 、sizePolicy Strategies for

1.Fixed

 

 2.Minimum

 3.Maximum

There may be a little problem in the summary , You'd better try it yourself