zhonghua

當你使用QStandardItemModel(model)與QTableView顯示數據時, 如果數據量比較大, 如幾千上萬條, 每次給model填充數據時, 只是使用model->clear()來清空數據, 然后再填充, 速度會非常的慢. 但如果是使用delete model; model = new QStandardItemModel()顯示的刪除model, 然后再創建一個model, 這樣顯示速度會非常的快, 不知何故.
例子：

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

QStandardItemModel *model = new QStandardItemModel();
QTableView *table = new QTableView();

// 如果事先給 table設置了 model而不預指定好要存儲的數據的行數，則會非常慢
// table->setModel(model); /// [[1]]
// model->setRowCount(1000); /// [[1]]

model->setColumnCount(14);

for (int i = 0; i < 1000; ++i) {
model->setItem(i, 0, new QStandardItem("1"));
model->setItem(i, 1, new QStandardItem("2"));
model->setItem(i, 2, new QStandardItem("3"));
model->setItem(i, 3, new QStandardItem("4"));
model->setItem(i, 4, new QStandardItem("5"));
model->setItem(i, 5, new QStandardItem("6"));
model->setItem(i, 6, new QStandardItem("7"));
model->setItem(i, 7, new QStandardItem("8"));
model->setItem(i, 8, new QStandardItem("9"));
model->setItem(i, 9, new QStandardItem("10"));
model->setItem(i, 10, new QStandardItem("11"));
model->setItem(i, 11, new QStandardItem("12"));
model->setItem(i, 12, new QStandardItem("13"));
model->setItem(i, 13, new QStandardItem("14"));
}

I'm building my own custom event and I want to just put this out there to
see if anyone is offended by the way I use the registerEventType function
(since I can't find any specific info on how to use it).  I think it make
sense... but I've never casted a new value into a predefined enum... and I
fear change.

ShapeAnimationEvent.h:

#ifndef SHAPE_ANIMATION_EVENT_H
#define SHAPE_ANIMATION_EVENT_H

#include <QEvent>
#include <QVariant>

class ShapeAnimationEvent : public QEvent
{
public:
    static const QEvent::Type JUMP_TO_TIME;

    ShapeAnimationEvent(QEvent::Type type, QVariant data);
    QVariant data() const;

private:
    QVariant m_data;

};

#endif

ShapeAnimationEvent.cpp:

#include "ShapeAnimationEvent.h"

const QEvent::Type ShapeAnimationEvent::JUMP_TO_TIME =
(QEvent::Type)QEvent::registerEventType();

ShapeAnimationEvent::ShapeAnimationEvent(QEvent::Type type, QVariant data) :
QEvent(type), m_data(data)
{

}

QVariant ShapeAnimationEvent::data() const
{
    return m_data;
}

Thanks,
Brian!