Qt利用QTableWidget实现磁盘容量显示支持U盘或者SD卡到达信号

磁盘容量统计控件，说白了，就是用来统计本地盘符占用的容量，包括但不限于已用空间、剩余空间、总大小、已用百分比等，其中对应的百分比采用进度条显示，该进度条的前景色和背景色及文字颜色可以设置，在整体换肤的时候就需要用到。
本控件的基本上没有难点可言，就是兼容WIN和LINUX操作系统，在WIN上采用winapi去读取，linux采用QProcess去执行对应的命令（df -h）获取结果，然后定时器执行，关联信号槽获取返回的额数据解析即可，控件的应用场景主要是在一些嵌入式设备上面，方便用户查看当前还剩余多少空间。

主要功能：
1. 可自动加载本地存储设备的总容量/已用容量
2. 进度条显示已用容量
3. 支持所有操作系统
4. 增加U盘或者SD卡到达信号

## 二、代码思路
```c++
void DeviceSizeTable::load()
{
    //清空原有数据
    int row = this->rowCount();
    for (int i = 0; i < row; i++) {
        this->removeRow(0);
    }

#ifdef Q_OS_WIN
    QFileInfoList list = QDir::drives();
    foreach (QFileInfo dir, list) {
        QString dirName = dir.absolutePath();
        LPCWSTR lpcwstrDriver = (LPCWSTR)dirName.utf16();
        ULARGE_INTEGER liFreeBytesAvailable, liTotalBytes, liTotalFreeBytes;

        if (GetDiskFreeSpaceEx(lpcwstrDriver, &liFreeBytesAvailable, &liTotalBytes, &liTotalFreeBytes)) {
            QString use = QString::number((double)(liTotalBytes.QuadPart - liTotalFreeBytes.QuadPart) / GB, 'f', 1);
            use += "G";
            QString free = QString::number((double) liTotalFreeBytes.QuadPart / GB, 'f', 1);
            free += "G";
            QString all = QString::number((double) liTotalBytes.QuadPart / GB, 'f', 1);
            all += "G";
            int percent = 100 - ((double)liTotalFreeBytes.QuadPart / liTotalBytes.QuadPart) * 100;
            insertSize(dirName, use, free, all, percent);
        }
    }

#else
    process->start("df -h");
#endif
}

void DeviceSizeTable::readData()
{
    while (!process->atEnd()) {
        QString result = QLatin1String(process->readLine());
#ifdef __arm__
        if (result.startsWith("/dev/root")) {
            checkSize(result, "本地存储");
        } else if (result.startsWith("/dev/mmcblk")) {
            checkSize(result, "本地存储");
        } else if (result.startsWith("/dev/mmcblk1p")) {
            checkSize(result, "SD卡");
            QStringList list = result.split(" ");
            emit sdcardReceive(list.at(0));
        } else if (result.startsWith("/dev/sd")) {
            checkSize(result, "U盘");
            QStringList list = result.split(" ");
            emit udiskReceive(list.at(0));
        }
#else
        if (result.startsWith("/dev/sd")) {
            checkSize(result, "");
            QStringList list = result.split(" ");
            emit udiskReceive(list.at(0));
        }
#endif
    }
}

void DeviceSizeTable::checkSize(const QString &result, const QString &name)
{
    QString dev, use, free, all;
    int percent = 0;
    QStringList list = result.split(" ");
    int index = 0;

    for (int i = 0; i < list.count(); i++) {
        QString s = list.at(i).trimmed();
        if (s == "") {
            continue;
        }

        index++;
        if (index == 1) {
            dev = s;
        } else if (index == 2) {
            all = s;
        } else if (index == 3) {
            use = s;
        } else if (index == 4) {
            free = s;
        } else if (index == 5) {
            percent = s.left(s.length() - 1).toInt();
            break;
        }
    }

    if (name.length() > 0) {
        dev = name;
    }

    insertSize(dev, use, free, all, percent);
}

void DeviceSizeTable::insertSize(const QString &name, const QString &use, const QString &free, const QString &all, int percent)
{
    int row = this->rowCount();
    this->insertRow(row);

    QTableWidgetItem *itemname = new QTableWidgetItem(name);
    QTableWidgetItem *itemuse = new QTableWidgetItem(use);
    itemuse->setTextAlignment(Qt::AlignCenter);
    QTableWidgetItem *itemfree = new QTableWidgetItem(free);
    itemfree->setTextAlignment(Qt::AlignCenter);
    QTableWidgetItem *itemall = new QTableWidgetItem(all);
    itemall->setTextAlignment(Qt::AlignCenter);

    this->setItem(row, 0, itemname);
    this->setItem(row, 1, itemuse);
    this->setItem(row, 2, itemfree);
    this->setItem(row, 3, itemall);

    QProgressBar *bar = new QProgressBar;
    bar->setRange(0, 100);
    bar->setValue(percent);

    QString qss = QString("QProgressBar{background:%1;border-width:0px;border-radius:0px;text-align:center;}"
                          "QProgressBar::chunk{border-radius:0px;}").arg(bgColor.name());

    if (percent < 50) {
        qss += QString("QProgressBar{color:%1;}QProgressBar::chunk{background:%2;}").arg(textColor1.name()).arg(chunkColor1.name());
    } else if (percent < 90) {
        qss += QString("QProgressBar{color:%1;}QProgressBar::chunk{background:%2;}").arg(textColor2.name()).arg(chunkColor2.name());
    } else {
        qss += QString("QProgressBar{color:%1;}QProgressBar::chunk{background:%2;}").arg(textColor3.name()).arg(chunkColor3.name());
    }

    bar->setStyleSheet(qss);
    this->setCellWidget(row, 4, bar);
}
```

## 三、效果图

原文地址：http://www.qtcn.org/bbs/read-htm-tid-88627-ds-1.html