QT笔记:代理(Delegate)小结

用户实现代理类时，可以从两个类中继承

第一种：从QAbstractItemDelegate类中继承，至少需要实现两个函数，paint()和sizeHint()

void MyDelegate::paint(QPainter*painter,const QStyleOptionViewItem&option, constQModelIndex&index)const
{
    if (index.column() == 需代理的列) {
        int content = index.model()->data(index, Qt::DisplayRole).toInt(); // 取到模型中原来的内容
        // ... 修改取到的值，代码略                QStyleOptionViewItem myOption = option;
        myOption.displayAlignment = Qt::AlignRight | Qt::AlignVCenter; // 处理文本的对齐方式 (不重要)

        drawDisplay(painter, myOption, myOption.rect, 修改后的值); // 写回处理后的值
        drawFocus(painter, myOption, myOption.rect); // 如果当前项具有焦点，它就绘制一个焦点矩形(不重要)
    } else{
        QItemDelegate::paint(painter, option, index);
    }
}

QSize MyDelegate::sizeHint(const QStyleOptionViewItem &option, const QModelIndex &index) const
{    
    if (条件) {
        return Qsize(int width, int height); // 用户定义
    } else {
        return QStyledItemDelegate::sizeHint(option, index);
    }
}

 

第二种：从QItemDelegate类继承，一般使用这种方式，减少代码量

.h文件

#ifndef DELEGATE_H
#define DELEGATE_H

#include <QItemDelegate>
#include <QModelIndex>
#include <QObject>
#include <QSize>
#include <QSpinBox>

class SpinBoxDelegate : public QItemDelegate
{
    Q_OBJECT

public:
    SpinBoxDelegate(QObject *parent = 0);

    QWidget *createEditor(QWidget *parent, const QStyleOptionViewItem &option, const QModelIndex &index) const;

    void setEditorData(QWidget *editor, const QModelIndex &index) const;
    void setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const;

    void updateEditorGeometry(QWidget *editor, const QStyleOptionViewItem &option, const QModelIndex &index) const;
};
#endif

.cpp文件

SpinBoxDelegate::SpinBoxDelegate(QObject *parent)
    : QItemDelegate(parent)
{
}

QWidget *SpinBoxDelegate::createEditor(QWidget *parent, const QStyleOptionViewItem &/* option */,
    const QModelIndex &/* index */) const
{
    QSpinBox *editor = new QSpinBox(parent);
    editor->setMinimum(0);
    editor->setMaximum(100);

    return editor;
}

void SpinBoxDelegate::setEditorData(QWidget *editor, const QModelIndex &index) const
{
    int value = index.model()->data(index, Qt::EditRole).toInt();

    QSpinBox *spinBox = static_cast<QSpinBox*>(editor);
    spinBox->setValue(value);
}

void SpinBoxDelegate::setModelData(QWidget *editor, QAbstractItemModel *model,
                                   const QModelIndex &index) const
{
    QSpinBox *spinBox = static_cast<QSpinBox*>(editor);
    spinBox->interpretText();
    int value = spinBox->value();

    model->setData(index, value, Qt::EditRole);
}

void SpinBoxDelegate::updateEditorGeometry(QWidget *editor,
    const QStyleOptionViewItem &option, const QModelIndex &/* index */) const
{
    editor->setGeometry(option.rect); // option.rect属性中保存了条目的位置，这里将控件设置在刚好占住条目的位置
}