今天簡單說一下Qt的樹形控件，在Qt中樹形控件的名稱叫做QTreeWidget,而控件里的樹節(jié)點的名稱叫做QTreeWidgetItem。今天這 里講的是如何創(chuàng)建具有復(fù)選框的樹形控件，這種控件其實有時挺有用的，如飛信群發(fā)短信時的選擇聯(lián)系人的界面中就使用了有復(fù)選框的樹形控件。先來看一下長什么 樣的：

當選中頂層的樹形節(jié)點時，子節(jié)點全部被選中，當取消頂層樹形節(jié)點時，子節(jié)點全部被取消選中狀態(tài)，而當選中子節(jié)點時，父節(jié)點顯示部分選中的狀態(tài)。

      要實現(xiàn)這種界面其實很簡單的。在Qt的設(shè)計器中，拖出一個QTreeWidget，然后在主窗口中寫一個函數(shù)init初始化界面，連接樹形控件的節(jié)點改變 信號itemChanged(QTreeWidgetItem* item, int column)，實現(xiàn)這個信號的即可。下面是具體代碼：

      ui.setupUi(this);

       //初始化
        init();

     //連接信號和槽

      connect(ui.treeWidget, SIGNAL(itemChanged(QTreeWidgetItem*, int)), this, SLOT(treeItemChanged(QTreeWidgetItem*, int)));

void TreeWidgetTest::init()
{
    ui.treeWidget->clear();

   //第一個分組
   QTreeWidgetItem *group1 = new QTreeWidgetItem(ui.treeWidget);
   group1->setText(0, "group1");
   group1->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
   group1->setCheckState(0, Qt::Unchecked);

   QTreeWidgetItem *subItem11 = new QTreeWidgetItem(group1);
   subItem11->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
   subItem11->setText(0, "subItem11");
   subItem11->setCheckState(0, Qt::Unchecked);

   QTreeWidgetItem *subItem12 = new QTreeWidgetItem(group1);
   subItem12->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
   subItem12->setText(0, "subItem12");
   subItem12->setCheckState(0, Qt::Unchecked);

  QTreeWidgetItem *subItem13 = new QTreeWidgetItem(group1);
  subItem13->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
  subItem13->setText(0, "subItem13");
  subItem13->setCheckState(0, Qt::Unchecked);

  QTreeWidgetItem *subItem14 = new QTreeWidgetItem(group1);
  subItem14->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
  subItem14->setText(0, "subItem14");
  subItem14->setCheckState(0, Qt::Unchecked);

//第二個分組
  QTreeWidgetItem *group2 = new QTreeWidgetItem(ui.treeWidget);
  group2->setText(0, "group2");
  group2->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
  group2->setCheckState(0, Qt::Unchecked);

  QTreeWidgetItem *subItem21 = new QTreeWidgetItem(group2);
  subItem21->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
  subItem21->setText(0, "subItem21");
  subItem21->setCheckState(0, Qt::Unchecked);

  QTreeWidgetItem *subItem22 = new QTreeWidgetItem(group2);
  subItem22->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
  subItem22->setText(0, "subItem22");
  subItem22->setCheckState(0, Qt::Unchecked);

  QTreeWidgetItem *subItem23 = new QTreeWidgetItem(group2);
  subItem23->setFlags(Qt::ItemIsUserCheckable | Qt::ItemIsEnabled | Qt::ItemIsSelectable);
  subItem23->setText(0, "subItem23");
  subItem23->setCheckState(0, Qt::Unchecked);

}

void TreeWidgetTest::treeItemChanged(QTreeWidgetItem* item, int column)
{
  QString itemText = item->text(0);
  //選中時
if (Qt::Checked == item->checkState(0))
{
   QTreeWidgetItem* parent = item->parent();
   int count = item->childCount();
   if (count > 0)
   {
    for (int i = 0; i < count; i++)
    {
     //子節(jié)點也選中
     item->child(i)->setCheckState(0, Qt::Checked);
    }   
   }
   else
   {
    //是子節(jié)點
    updateParentItem(item);
   }
}
else if (Qt::Unchecked == item->checkState(0))
{
   int count = item->childCount();
   if (count > 0)
   {
    for (int i = 0; i < count; i++)
    {
     item->child(i)->setCheckState(0, Qt::Unchecked);
    }
   }
   else
   {
    updateParentItem(item);
   }
}

}

void TreeWidgetTest::updateParentItem(QTreeWidgetItem* item)
{
QTreeWidgetItem *parent = item->parent();
if (parent == NULL)
{
   return;
}

//選中的子節(jié)點個數(shù)
int selectedCount = 0;
int childCount = parent->childCount();
for (int i = 0; i < childCount; i++)
{
   QTreeWidgetItem *childItem = parent->child(i);
   if (childItem->checkState(0) == Qt::Checked)
   {
    selectedCount++;
   }
}

if (selectedCount <= 0)
{
   //選中狀態(tài)
   parent->setCheckState(0, Qt::Unchecked);
}
else if (selectedCount > 0 && selectedCount < childCount)
{
   //部分選中狀態(tài)
   parent->setCheckState(0, Qt::PartiallyChecked);
}
else if (selectedCount == childCount)
{
  //未選中狀態(tài)
   parent->setCheckState(0, Qt::Checked);
}

//changeFromUser = true;

}

      上面需要注意的是，當用代碼setCheckState后，會觸發(fā)itemChanged事件，有時這個會帶來麻煩，這時需要加一些標志來判斷是由用戶操作產(chǎn)生的還是程序本身代碼產(chǎn)生的。