Qt程序测试错误

Question

我正试图从qt书中编译对话程序。我一直得到这个错误:

:'QLabel':类没有构造函数

职业:

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:

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

头:

#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

实现:

#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

:'QLabel':类没有构造函数

似乎你包括QtGui而不是QtWidgets。替换这一行:

#include <QtGui>

#include <QtWidgets>

如果您正在使用Qt 5构建。这本书是为Qt 4编写的，小部件类被移到了它们自己的模块中。

免责声明:包含整个模块是一个坏主意。

Answer 2

当用Qt 4编写的程序在Qt 5中编译时就会出现这个问题

解决方案是:

1. 在.pro文件中添加以下行:

QT += core gui widgets

1. 包含以下头文件:

#include <QtWidgets>