在“使用 Qt 4 进行 C++ GUI 编程”一书中，第 1 部分第 2 章中逐步显示了 FindDialog Widget 示例，现在我正在尝试使用 qmake 生成的 Makefile 构建此示例，但它抱怨说：
g++ -Wl,-O1 -o Hello hello.o -L/usr/lib/i386-linux-gnu -lQtGui -lQtCore -lpthread
hello.o: In function `main':
hello.cpp:(.text.startup+0x47): undefined reference to `FindDialog::FindDialog(QWidget*)'
collect2: ld returned 1 exit status
make: *** [Hello] Error 1
使用 shell 命令提示符（在 Linux Mint 上）我创建了一个目录 Hello 我创建了一个项目文件（使用 qmake）Hello.pro 这是 /Hello 中的 ls 命令输出：
FindDialog.cpp FindDialog.h hello.cpp hello.o Hello.pro Makefile
我一直在尝试找出问题 2 小时，我将非常感谢任何帮助，谢谢。
这是包含 main 的文件：
#include "FindDialog.h"
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
FindDialog *dialog = new FindDialog();
dialog->show();
return app.exec();
}
头文件：FindDialog.h
#ifndef FIND_DIALOG_H
#define FIND_DIALOG_H
#include <QDialog>
class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;
class FindDialog : public QDialog
{
Q_OBJECT
public:
FindDialog(QWidget* parent = 0);
~FindDialog();
signals:
void findNext(const QString &str, Qt::CaseSensitivity cs);
void findPrevious(const QString &str, Qt::CaseSensitivity cs);
private slots:
void findClicked();
void enableFindFunction(const QString &text);
private:
QLabel *label;
QLineEdit *lineEdit;
QCheckBox *caseCheckBox;
QCheckBox *backwardCheckBox;
QPushButton *findButton;
QPushButton *closeButton;
};
#endif
实施文件：FindDialog.cpp
#include <QtGui>
#include "FindDialog.h"
FindDialog::FindDialog(QWidget *parent = 0):QDialog(parent)
{
//Creating components
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"));
//adding event handling
connect(lineEdit, SIGNAL(textChanged(const QString &)), this, SLOT(enableFindButton(const QString &)));
connect(findButton, SIGNAL(clicked()), this, SLOT(findClicked()));
connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));
//setting layout
QHBoxLayout *topLeftLayout = new QHBoxLayout;
topLeftLayout->addWidget(label);
topLeftLayout->addWidget(lineEdit);
QVBoxLayout *leftLayout = new QVBoxLayout;
leftLayout->addLayout(topLeftLayout);
leftLayout->addWidget(caseCheckBox);
leftLayout->addWidget(backwardCheckBox);
QVBoxLayout *rightLayout = new QVBoxLayout;
rightLayout->addWidget(findButton);
rightLayout->addWidget(closeButton);
rightLayout->addStretch();
QHBoxLayout *mainLayout = new QHBoxLayout;
mainLayout->addLayout(leftLayout);
mainLayout->addLayout(rightLayout);
setLayout(mainLayout);
//window title
setWindowTitle(tr("Find"));
setFixedHeight(sizeHint().height());
}
FindDialog::~FindDialog(){
}
void FindDialog::findClicked()
{
QString text = lineEdit->text();
Qt::CaseSensitivity cs = caseCheckBox->isChecked() ? Qt::CaseSensitive : Qt::CaseInsensitive;
if (backwardCheckBox->isChecked()) {
emit findPrevious(text, cs);
}
else {
emit findNext(text, cs);
}
}
void FindDialog::enableFindButton(const QString &text)
{
findButton->setEnabled(!text.isEmpty());
}