在工作中我们会经常使用到树状结构,例如Windows的资源管理器中的目录结构就用到了类似的控件。在Qt中可以使用QTreeWidget来实现类似的效果。
Qt中提供的QTreeWidget功能相对比较少,在实际中经常需要扩展它的功能,比如本文将要谈到的三态树的问题。
首先我们先创建一个QTreeWidget的对象,并添加一些节点:
void WidgetTreeTEST::createDirectoryStruct() { QTreeWidgetItem *topLevelDirectory = new QTreeWidgetItem(); topLevelDirectory->setText(0, "DIR"); topLevelDirectory->setCheckState(0, Qt::Checked); topLevelDirectory->setIcon(0, QIcon(":/Resources/folder.png")); //Direcoty C QTreeWidgetItem *directoryC = new QTreeWidgetItem(); directoryC->setText(0, "LocalDrive C"); directoryC->setCheckState(0, Qt::Checked); directoryC->setIcon(0, QIcon(":/Resources/folder.png")); QTreeWidgetItem *file1 = new QTreeWidgetItem(); file1->setText(0, "file1"); file1->setCheckState(0, Qt::Checked); file1->setIcon(0, QIcon(":/Resources/file.png")); QTreeWidgetItem *file2 = new QTreeWidgetItem(); file2->setText(0, "file2"); file2->setCheckState(0, Qt::Checked); file2->setIcon(0, QIcon(":/Resources/file.png")); directoryC->addChild(file1); directoryC->addChild(file2); //Directory D QTreeWidgetItem *directoryD = new QTreeWidgetItem(); directoryD->setText(0, "LocalDrive D"); directoryD->setCheckState(0, Qt::Checked); directoryD->setIcon(0, QIcon(":/Resources/folder.png")); QTreeWidgetItem *file3 = new QTreeWidgetItem(); file3->setText(0, "file3"); file3->setCheckState(0, Qt::Checked); file3->setIcon(0, QIcon(":/Resources/file.png")); directoryD->addChild(file3); //Direcoty E QTreeWidgetItem *directoryE = new QTreeWidgetItem(); directoryE->setText(0, "LocalDrive E"); directoryE->setCheckState(0, Qt::Checked); directoryE->setIcon(0, QIcon(":/Resources/folder.png")); QTreeWidgetItem *file4 = new QTreeWidgetItem(); file4->setText(0, "file4"); file4->setCheckState(0, Qt::Checked); file4->setIcon(0, QIcon(":/Resources/file.png")); QTreeWidgetItem *file5 = new QTreeWidgetItem(); file5->setText(0, "file5"); file5->setCheckState(0, Qt::Checked); file5->setIcon(0, QIcon(":/Resources/file.png")); QTreeWidgetItem *direcotryE1 = new QTreeWidgetItem(); direcotryE1->setText(0, "file6"); direcotryE1->setCheckState(0, Qt::Checked); direcotryE1->setIcon(0, QIcon(":/Resources/folder.png")); QTreeWidgetItem *file6 = new QTreeWidgetItem(); file6->setText(0, "file6"); file6->setCheckState(0, Qt::Checked); file6->setIcon(0, QIcon(":/Resources/file.png")); direcotryE1->addChild(file6); directoryE->addChild(file4); directoryE->addChild(file5); directoryE->addChild(direcotryE1); QList<QTreeWidgetItem*> topLevelItemList; topLevelItemList << directoryC << directoryD << directoryE; topLevelDirectory->addChildren(topLevelItemList); addTopLevelItem(topLevelDirectory); }创建的场景结构如下图所示:
在QTreeWidget中树结构的每一项都是一个QTreeWidgetItem,通过对它的设置可以修改树的显示效果,对于树的三态切换需要处理QTreeWidget中的一个信号:
当某一个节点被选中或者取消选中的时候需要处理以下情况:
1. 处理该节点的子节点(如果它有子节点),它的子节点的状态(Check或者Uncheck)和它一样 (如果它的子节点中有目录,那么还需要递归处理子节点的子节点)
2. 处理该节点的父节点,父节点会根据当前它子节点的状态来调整自身的状态(如果该父节点还有父节点,那么还需要递归处理父节点的父节点)
在QTreeWidget中的itemChanged事件会一直递归的调用,也就是说如果我们设置了子节点的状态(使用程序设置,或者手动点击),那么被设置的节点会继续调用itemChanged信号,根据这个特点,我们在编写代码的过程中不需要考虑递归的问题,只需要设置一个层级的处理即可。
具体实现如下:
设置子节点和父节点的状态
void WidgetTreeTEST::setChildCheckState(QTreeWidgetItem *item, Qt::CheckState cs) { if(!item) return; for (int i=0;i<item->childCount();i++) { QTreeWidgetItem* child=item->child(i); if(child->checkState(0)!=cs) { child->setCheckState(0, cs); } } setParentCheckState(item->parent()); } void WidgetTreeTEST::setParentCheckState(QTreeWidgetItem *item) { if(!item) return; int selectedCount=0; int childCount = item->childCount(); for (int i=0;i<childCount;i++) { QTreeWidgetItem* child= item->child(i); if(child->checkState(0)==Qt::Checked) { selectedCount++; } } if(selectedCount == 0) { item->setCheckState(0,Qt::Unchecked); } else if (selectedCount == childCount) { item->setCheckState(0,Qt::Checked); } else { item->setCheckState(0,Qt::PartiallyChecked); } }在信号的响应槽函数中:
void WidgetTreeTEST::itemChangedSlot(QTreeWidgetItem* item, int column) { if(Qt::PartiallyChecked!=item->checkState(0)) setChildCheckState(item,item->checkState(0)); if(Qt::PartiallyChecked==item->checkState(0)) if(!isTopItem(item)) item->parent()->setCheckState(0,Qt::PartiallyChecked); } bool WidgetTreeTEST::isTopItem(QTreeWidgetItem* item) { if(!item) return false; if(!item->parent()) return true; return false; }槽函数中根据PartiallyChecked进行分类:因为只有组节点(包含子节点的节点)才可能有partiallyChecked的状态,当组节点被设置为partiallyChecked的时候它的父节点也会被设置为这种类型的状态,并且当组节点设置为PartiallyChecked的时候对子节点的状态没有任何影响。
最后结果如下图所示: