帶動態變化內容的QScrollArea

Question

我有一個帶有一些按鈕的QScrollArea，如圖片所示。

佈局的思路是： 1.左側和右側的按鈕應該被用於滾動按鈕的時候都太寬

2.數字在滾動區域的按鈕可以改變動態 3.應儘可能使用任何空閒空間來擴大滾動區域。如果沒有這樣的空間存在導航按鈕應該用於滾動。

以我目前的執行情況時，我提高了按鈕，我有這樣的：

但在右邊的自由空間，所以這應該是這樣的：

如果我增加一次，以10例如，那麼應該出現滾動條（因爲佈局是由小部件固定的）。

我想知道是否有任何其他方式除了小部件的手動調整大小（因爲UI可以翻譯和按鈕可以改變大小也暗示真正的設計更爲複雜:(

這裏是我的實現在ScrollAreaTest widget的：

#include "MainWidget.h" 

#include <QLineEdit> 
#include <QVBoxLayout> 
#include <QHBoxLayout> 
#include <QScrollArea> 
#include <QPushButton> 
#include <QDebug> 
#include "ButtonWidget.h" 

#include "CheckableButtonGroup.h" 

MainWidget::MainWidget(QWidget *parent) 
    : QWidget(parent), 
     m_scrollArea(0), 
     m_lineEdit(0), 
     m_buttons(0) 
{ 
    QVBoxLayout* mainLayout = new QVBoxLayout(this); 
    QWidget* firstRow = new QWidget; 
    QHBoxLayout* firstRowLayout = new QHBoxLayout(firstRow); 

    QPushButton* left = new QPushButton; 
    QPushButton* right = new QPushButton; 

    m_buttons = new CheckableButtonGroup(Qt::Horizontal); 
    m_buttons->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Preferred); 
    m_buttons->setButtonsCount(5); 
    m_buttons->setStyleSheet("border: none"); 

    QWidget* const buttonsContainer = new QWidget; 
    QHBoxLayout* const buttonsContainerLayout = new QHBoxLayout(buttonsContainer); 
    buttonsContainerLayout->setSpacing(0); 
    buttonsContainerLayout->setSizeConstraint(QLayout::SetMinAndMaxSize); 
    buttonsContainerLayout->setMargin(0); 
    buttonsContainerLayout->addWidget(m_buttons, 0, Qt::AlignLeft); 

    qDebug() << m_buttons->buttons()[ 0 ]->size(); 

    m_scrollArea = new QScrollArea; 
    m_scrollArea->setContentsMargins(0, 0, 0, 0); 
    m_scrollArea->setWidget(buttonsContainer); 
    m_scrollArea->setWidgetResizable(true); 
    m_scrollArea->setStyleSheet("border: 1px solid blue"); 
    m_scrollArea->setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Preferred); 

    firstRowLayout->addWidget(left  , 0, Qt::AlignLeft); 
    firstRowLayout->addWidget(m_scrollArea, 1, Qt::AlignLeft); 
    firstRowLayout->addWidget(right  , 0, Qt::AlignLeft); 

    m_lineEdit = new QLineEdit; 
    QPushButton* button = new QPushButton; 
    QHBoxLayout* secondRowLayout = new QHBoxLayout; 
    secondRowLayout->addWidget(m_lineEdit); 
    secondRowLayout->addWidget(button); 

    connect(button, SIGNAL(clicked()), SLOT(setButtonsCount())); 

    mainLayout->addWidget(firstRow, 1, Qt::AlignLeft); 
    mainLayout->addLayout(secondRowLayout); 

    button->setText("Set buttons count"); 

    buttonsContainer->resize(m_buttons->buttonsOptimalWidth(), buttonsContainer->height()); 
    m_buttons->resize(m_buttons->buttonsOptimalWidth(), m_buttons->height()); 

    //area->resize(100, area->height()); 
    //area->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff); 
} 

MainWidget::~MainWidget() 
{ 
} 

void MainWidget::setButtonsCount() 
{ 
    m_buttons->setButtonsCount(m_lineEdit->text().toInt()); 
} 

這裏是包含了存在問題的整個Qt工程： https://drive.google.com/file/d/0B-mc4aKkzWlxQzlPMEVuNVNKQjg/edit?usp=sharing

Answer 1

的基本步驟是：

1. 容納按鈕的容器小部件（您的CheckableButtonGroup）必須具有QLayout::SetMinAndMaxSize大小約束集。那麼它將會足夠大以容納按鈕。它的尺寸政策並不重要，因爲您只需將其放入QScrollArea，而不是放入其他佈局。

2. 滾動區域需要根據其保存的窗口小部件的大小設置其最大大小。默認實現不會這樣做，所以必須通過監視嵌入的小部件的調整大小事件來實現它。

下面的代碼是一個在Qt 4.8和5.2下工作的最簡單的例子。

// https://github.com/KubaO/stackoverflown/tree/master/questions/scrollgrow-21253755 
#include <QtGui> 
#if QT_VERSION >= QT_VERSION_CHECK(5,0,0) 
#include <QtWidgets> 
#endif 

class ButtonGroup : public QWidget { 
    Q_OBJECT 
    QHBoxLayout m_layout{this}; 
public: 
    ButtonGroup(QWidget * parent = 0) : QWidget{parent} { 
     m_layout.setSizeConstraint(QLayout::SetMinAndMaxSize); // <<< Essential 
    } 
    Q_SLOT void addButton() { 
     auto n = m_layout.count(); 
     m_layout.addWidget(new QPushButton{QString{"Btn #%1"}.arg(n+1)}); 
    } 
}; 

class AdjustingScrollArea : public QScrollArea { 
    bool eventFilter(QObject * obj, QEvent * ev) { 
     if (obj == widget() && ev->type() == QEvent::Resize) { 
     // Essential vvv 
     setMaximumWidth(width() - viewport()->width() + widget()->width()); 
     } 
     return QScrollArea::eventFilter(obj, ev); 
    } 
public: 
    AdjustingScrollArea(QWidget * parent = 0) : QScrollArea{parent} {} 
    void setWidget(QWidget *w) { 
     QScrollArea::setWidget(w); 
     // It happens that QScrollArea already filters widget events, 
     // but that's an implementation detail that we shouldn't rely on. 
     w->installEventFilter(this); 
    } 
}; 

class Window : public QWidget { 
    QGridLayout   m_layout{this}; 
    QLabel    m_left{">>"}; 
    AdjustingScrollArea m_area; 
    QLabel    m_right{"<<"}; 
    QPushButton   m_add{"Add a widget"}; 
    ButtonGroup   m_group; 
public: 
    Window() { 
     m_layout.addWidget(&m_left, 0, 0); 
     m_left.setSizePolicy(QSizePolicy::Maximum, QSizePolicy::Preferred); 
     m_left.setStyleSheet("border: 1px solid green"); 

     m_layout.addWidget(&m_area, 0, 1); 
     m_area.setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::Preferred); 
     m_area.setStyleSheet("QScrollArea { border: 1px solid blue }"); 
     m_area.setWidget(&m_group); 
     m_layout.setColumnStretch(1, 1); 

     m_layout.addWidget(&m_right, 0, 2); 
     m_right.setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Preferred); 
     m_right.setStyleSheet("border: 1px solid green"); 

     m_layout.addWidget(&m_add, 1, 0, 1, 3); 
     connect(&m_add, SIGNAL(clicked()), &m_group, SLOT(addButton())); 
    } 
}; 

int main(int argc, char *argv[]) 
{ 
    QApplication a{argc, argv}; 
    Window w; 
    w.show(); 
    return a.exec(); 
} 

#include "main.moc"