Qt中secondaryColumnCombo->currentIndex()的疑问
（《c++ gui qt 4 编程》）
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在书中52页中有这样一段代码：
- C/C++ code
void MainWindow::sort(){ SortDialog dialog(this); QTableWidgetSelectionRange range = spreadsheet->selectedRange(); dialog.setColumnRange('A' + range.leftColumn(), 'A' + range.rightColumn()); if (dialog.exec()) { SpreadsheetCompare compare; compare.keys[0] = dialog.primaryColumnCombo->currentIndex(); compare.keys[1] = dialog.secondaryColumnCombo->currentIndex() - 1; compare.keys[2] = dialog.tertiaryColumnCombo->currentIndex() - 1; compare.ascending[0] = (dialog.primaryOrderCombo->currentIndex() == 0); compare.ascending[1] = (dialog.secondaryOrderCombo->currentIndex() == 0); compare.ascending[2] = (dialog.tertiaryOrderCombo->currentIndex() == 0); spreadsheet->sort(compare); }}哪位大大能详细解释一下
- C/C++ code
dialog.primaryColumnCombo->currentIndex(); compare.keys[1] = dialog.secondaryColumnCombo->currentIndex() - 1; compare.keys[2] = dialog.tertiaryColumnCombo->currentIndex() - 1;
这几句啊，实在是看不懂，为毛要-1啊（书上说考虑到“none”项，从当前项-1）。还有，currentIndex()函数的索引值怎么算啊，是不是上述代码中key[]最后的值为{0,0,1}啊（如果如书中P52图3.14所示，选中A1到C7）
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组合框中没数据时返回-1 索引是从0开始的 因为组合框中的第一项是“none” 不在计算范围之内
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