今天简单说一下Qt的树形控件，在Qt中树形控件的名称叫做QTreeWidget,而控件里的树节点的名称叫做QTreeWidgetItem。今天这 里讲的是如何创建具有复选框的树形控件，这种控件其实有时挺有用的，如飞信群发短信时的选择联系人的界面中就使用了有复选框的树形控件。先来看一下长什么 样的：
当选中顶层的树形节点时，子节点全部被选中，当取消顶层树形节点时，子节点全部被取消选中状态，而当选中子节点时，父节点显示部分选中的状态。
要实现这种界面其实很简单的。在Qt的设计器中，拖出一个QTreeWidget，然后在主窗口中写一个函数init初始化界面，连接树形控件的节点改变 信号itemChanged(QTreeWidgetItem* item, int column)，实现这个信号的即可。下面是具体代码：
ui.setupUi(this);
//初始化
init();
//连接信号和槽
connect(ui.treeWidget, SIGNAL(itemChanged(QTreeWidgetItem*, int)), this, SLOT(treeItemChanged(QTreeWidgetItem*, int)));
void TreeWidgetTest::init()
{
ui.treeWidget->clear();
//第一个分组
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);
//第二个分组
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);
//选中时
if (Qt::Checked == item->checkState(0))
{
QTreeWidgetItem* parent = item->parent();
int count = item->childCount();
if (count > 0)
{
for (int i = 0; i < count; i++)
{
//子节点也选中
item->child(i)->setCheckState(0, Qt::Checked);
}
}
else
{
//是子节点
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;
}
//选中的子节点个数
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)
{
//选中状态
parent->setCheckState(0, Qt::Unchecked);
}
else if (selectedCount > 0 && selectedCount < childCount)
{
//部分选中状态
parent->setCheckState(0, Qt::PartiallyChecked);
}
else if (selectedCount == childCount)
{
//未选中状态
parent->setCheckState(0, Qt::Checked);
}
//changeFromUser = true;
}
上面需要注意的是，当用代码setCheckState后，会触发itemChanged事件，有时这个会带来麻烦，这时需要加一些标志来判断是由用户操作产生的还是程序本身代码产生的。