目标：实现当点击QtreeWidget中的某个item的时候 切换stack的方法

过程：要做一个图书管理系统，主界面是类似于这样的
左边是类似于树形空间的东西，当点击左边的左边的窗体的时候，右边的窗口也会跟着切换。
为了实现这个功能，必须要有两个控件，QTreeWidget和QstackWidget;
以下是具体代码
1.Widge.h头文件 
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include<QStackedWidget>
#include<QTreeWidget>
#include<QTreeWidgetItem>
#include<QString>
#include<QLabel>
#include<QGridLayout>
#include<QHBoxLayout>
#include<QStringList>

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = 0);
    ~Widget();
private:
QStackedWidget *stackWindow;
QHBoxLayout *mainLayout;
QTreeWidget *treeWidget;
QTreeWidgetItem *parentItem1;
QTreeWidgetItem *parentItem2;
QTreeWidgetItem *childItem1;
QTreeWidgetItem *childItem2;
QLabel *parentLable1;
QLabel *parentLable2;
QLabel *childLable1;
QLabel *childLable2;
public slots:
void change1(QTreeWidgetItem* item1,int count1);

};

#endif // WIDGET_H
2.Widget.cpp具体的实现 
#include "widget.h"
#include<QObject>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
{

    //connect(treeWidget,SIGNAL(itemClicked(QTreeWidgetItem*,int)),this,SLOT(change1(QTreeWidgetItem*,int)));

    stackWindow =new QStackedWidget;
    mainLayout =new QHBoxLayout;
    treeWidget =new QTreeWidget(this);
    parentItem1=new QTreeWidgetItem(treeWidget,QStringList("parent1"));
    parentItem2=new QTreeWidgetItem(treeWidget,QStringList("parent2"));
    childItem1=new QTreeWidgetItem(parentItem1,QStringList("child1"));
    childItem2=new QTreeWidgetItem(parentItem2,QStringList("child2"));
    parentLable1=new QLabel("parentWindow1");
    parentLable2=new QLabel("parentWindow2");
    childLable1=new QLabel("childLable1");
    childLable2=new QLabel("childLable2");
    stackWindow->addWidget(parentLable1);
    stackWindow->addWidget(parentLable2);
    stackWindow->addWidget(childLable1);
    stackWindow->addWidget(childLable2);
    mainLayout->addWidget(treeWidget);
    mainLayout->addWidget(stackWindow);
   // stackWindow->setCurrentIndex(2);

    this->setLayout(mainLayout);
    //QObject::connect(treeWidget,SIGNAL(itemPressed(QTreeWidgetItem*,int)),this,SLOT(change1(QTreeWidgetItem* ,int )));//注释1
    QObject::connect(treeWidget,SIGNAL(itemClicked(QTreeWidgetItem*,int)),this,SLOT(change1(QTreeWidgetItem* ,int)));

}

Widget::~Widget()
{

}
void Widget::change1(QTreeWidgetItem *item1, int count1)
{
    QTreeWidgetItem *item=item1;
    if(item->text(count1)=="parent1")
    {
        stackWindow->setCurrentIndex(0);
    }
    else if(item->text(count1)=="parent2")
    {
        stackWindow->setCurrentIndex(1);
    }
    else if(item->text(count1)=="child1")
    {
        stackWindow->setCurrentIndex(2);
    }
    else if(item->text(count1)=="child2")
    {
        stackWindow->setCurrentIndex(3);
    }

}

注释1：
这两个连接中的槽函数的参数只能给出类型，而不能给出形参名；
这两个连接必须写在窗口初始化之后