Question

我试图从qt书中编译对话程序。我一直收到这个错误：

：＆＃39; QLabel＆＃39; ：class没有构造函数

亲：

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = untitled
TEMPLATE = app


SOURCES += main.cpp\
        mainwindow.cpp \
    finddialog.cpp

HEADERS  += mainwindow.h \
    finddialog.h

FORMS    += mainwindow.ui

主要：

#include <QApplication>
#include "finddialog.h"
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    FindDialog *dialog = new FindDialog;
    dialog->show();
    return app.exec();
}

部首：

#ifndef FINDDIALOG_H
#define FINDDIALOG_H

#include <QDialog>

class QCheckBox;
class QLabel;
class QLineEdit;
class QPushButton;
class QWidget;

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 findClicked();
    void enableFindButton(const QString &text);
private:
    QLabel *label;
    QLineEdit *lineEdit;
    QCheckBox *caseCheckBox;
    QCheckBox *backwardCheckBox;
    QPushButton *findButton;
    QPushButton *closeButton;
};

#endif // FINDDIALOG_H

实施：

#include <QtGui>

#include "finddialog.h"

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(QString)), this, SLOT(enableFindButton(QString)));
    connect(findButton, SIGNAL(clicked()), this, SLOT(findClicked()));
    connect(closeButton, SIGNAL(clicked()), this, SLOT(close()));

    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);

    setWindowTitle(tr("Find"));
    setFixedHeight(sizeHint().height());
}

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());
}

Answer 1

：＆＃39; QLabel＆＃39; ：class没有构造函数

似乎你包括QtGui而不是QtWidgets。替换此行：

#include <QtGui>

与

#include <QtWidgets>

如果您正在使用Qt 5构建。本书是为Qt 4编写的，并且小部件类已移至他们自己的模块中。

免责声明：包含整个模块是一个坏主意。

Answer 2

在Qt 5中编写用Qt 4编写的程序时出现此问题

解决方案是：

在.pro文件中添加以下行：

QT + =核心gui小部件

包含以下标题文件：

#include <QtWidgets>

Qt编程错误与测试

2 个答案: