如何在 QListWidget Qt 中锁定一个项目

Question

是否可以锁定 QListWidget 中的某个项目，例如当我按下一个按钮时，该项目保持选中状态？我试图查找它但我失败了

Answer 1

I really hope you can provide me with an example, since I am just a beginner

是的，我可以。我们开始吧：

testQListWidgetLockSelection.cc:

#include <set>

#include <QtWidgets>

class ListWidget: public QListWidget {

  public:
    using QListWidget::QListWidget;
    virtual ~ListWidget() = default;

    void lockSelection(bool lock);

    virtual void selectionChanged(
      const QItemSelection &selected,
      const QItemSelection &deselected) override;

  private:
    bool _lockSel = false;
    std::set<int> _selLocked;
    bool _lockResel = false;

    struct LockGuard {
      bool &lock;
      LockGuard(bool &lock): lock(lock) { lock = true; }
      ~LockGuard() { lock = false; }
    };
};

void ListWidget::lockSelection(bool lock)
{
  _lockSel = lock;
  if (_lockSel) {
    // store selected indices
    for (const QModelIndex &qMI : selectedIndexes()) _selLocked.insert(qMI.row());
  } else _selLocked.clear();
}

void ListWidget::selectionChanged(
  const QItemSelection& selected, const QItemSelection& deselected)
{
  if (_lockSel && !_lockResel) {
    const LockGuard lock(_lockResel);
    QItemSelection reselect;
    for (int row : _selLocked) {
      const QModelIndex qMI = model()->index(row, 0);
      reselect.select(qMI, qMI);
    }
    selectionModel()->select(reselect, QItemSelectionModel::Select);
  }
}

void populate(QListWidget& qLstView)
{
  for (int i = 1; i <= 20; ++i) {
    qLstView.addItem(QString("Item %1").arg(i));
  }
}

int main(int argc, char **argv)
{
  qDebug() << "Qt Version:" << QT_VERSION_STR;
  QApplication app(argc, argv);
  // setup GUI
  QWidget qWinMain;
  qWinMain.resize(640, 480);
  qWinMain.setWindowTitle("Lock Selection Demo");
  QVBoxLayout qVBox;
  QCheckBox qTglLockSel("Lock Selection");
  qVBox.addWidget(&qTglLockSel, false);
  ListWidget qLstView;
  qLstView.setSelectionMode(ListWidget::ExtendedSelection);
  qVBox.addWidget(&qLstView, true);
  qWinMain.setLayout(&qVBox);
  qWinMain.show();
  // install signal handlers
  QObject::connect(&qTglLockSel, &QCheckBox::toggled,
    &qLstView, &ListWidget::lockSelection);
  // fill GUI with sample data
  populate(qLstView);
  // runtime loop
  return app.exec();
}

演示：

注：

这个示例有一个弱点：它没有考虑在锁定选择后可以插入或删除项目。

为了加强这一点，成员函数 rowsInserted() and rowsAboutToBeRemoved() 也必须被覆盖，以分别更正 ListWidget::_selLocked 中的索引。

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