展示不是类名或者命名空间

显示不是类名或者命名空间

FindDialog::FindDialog(QWidget *parent):QDialog(parent)
{
    label=new QLabel(tr("Find &what:"));
    lineEdit=new QLineEdit;
    label->setBuddy(lineEdit);
    caseCheckBox=new QCheckBox(tr("Match &case"));
    backwardCheckBox=new QCheckBox(tr("Search &backward"));
    findButton=new QPushButton(tr("&Find"));
    findButton->setDefault(true);
    findButton->setEnabled(false);
    closeButton=new QPushButton(tr("&close"));
    connect(lineEdit,SIGNAL(textChanged(const QString &)),this,SLOT(enableFindButton()));
    connect(findButton,SIGNAL(clicked()),this,SLOT(findCliked()));
    connect(closeButton,SIGNAL(clicked()),this,SLOT(closdt()));
    QHBoxLayout *topleftLayout=new QHBoxLayout;
    topleftLayout->addWidget(label);

#ifndef HAHA_H
#define HAHA_H
#include <QDialog>
class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;

class FindDialog:public QDialog
{
    Q_OBJECT
public:
    FindDialog(QWidget *parent=0);
signals:
    void findNext(const QString &str,Qt::CaseSensitivity cs);
    void findPrevious(const QString &str,Qt::CaseSensitivity cs);
private slots:
    void findCliked();
    void enableFindButton(const QString &text);
private:
    QLabel *label;
    QLineEdit *lineEdit;
    QCheckBox *caseCheckBox;
    QCheckBox *backwardCheckBox;
    QPushButton *findButton;
    QPushButton *closeButton;
};

 但是我已经声明类啊 Qt4 gui书上的代码...
------解决方案--------------------