初学Qt,想在主窗口(QWidget)中单击一个按钮(QPushButton)时打开 一个对话框(QDialog)。
我使用的环境为:
Qt 版本:5.6.2 非商业版 Qt Creator 版本:4.0.3
最初的代码如下:
main.cpp
#include <QApplication>
#include <QPushButton>
#include <QHBoxLayout>
#include "finddialog.h"
void btnSearchClick();
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QWidget *winMain = new QWidget;
winMain->setWindowTitle("Open Dialog");
QPushButton *btnQuit = new QPushButton(QObject::tr("Quit"));
QObject::connect(btnQuit, SIGNAL(clicked()),&app, SLOT(quit()));
QPushButton *btnSearch = new QPushButton(QObject::tr("Search"));
QObject::connect(btnSearch, SIGNAL(clicked), &app, SLOT(btnSearchClick()));
QVBoxLayout *mainLayout = new QVBoxLayout;
mainLayout->addWidget(btnSearch);
mainLayout->addWidget(btnQuit);
winMain->setLayout(mainLayout);
winMain->show();
return app.exec();
}
void btnSearchClick() {
FindDialog *dlgFind = new FindDialog;
dlgFind->show();
}
下面finddialog.h和finddialog.cpp的代码取自于《C++ GUI Qt4编程》(第二版)(Jasmin、Mark著,闫锋欣等译 电子工业出版社)
finddialog.h代码:
#ifndef FINDDIALOG_H
#define FINDDIALOG_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 findClicked();
void enableFindButton(const QString &text);
private:
QLabel *lbFindWhat;
QLineEdit *edtFindStr;
QCheckBox *caseCheckBox;
QCheckBox *backwardCheckBox;
QPushButton *btnFind;
QPushButton *btnClose;
};
#endif // FINDDIALOG_H
finddialog.cpp代码:
#include <QtWidgets>
#include "finddialog.h"
FindDialog::FindDialog(QWidget *parent) : QDialog(parent) {
lbFindWhat = new QLabel(tr("Find &what:"));
//lbFindWhat = new QLabel;
lbFindWhat->setText(tr("Find &what"));
edtFindStr = new QLineEdit;
lbFindWhat->setBuddy(edtFindStr);
caseCheckBox = new QCheckBox(tr("Match &case"));
backwardCheckBox = new QCheckBox(tr("Search &backward"));
btnFind = new QPushButton(tr("&Find"));
btnFind->setDefault(true);
btnFind->setEnabled(false);
btnClose = new QPushButton(tr("Close"));
connect(edtFindStr, SIGNAL(textChanged(const QString &)), this, SLOT(enableFindButton(const QString &)));
connect(btnFind, SIGNAL(clicked()), this, SLOT(findClicked()));
connect(btnClose, SIGNAL(clicked()), this, SLOT(close()));
QHBoxLayout *topLevelLayout = new QHBoxLayout;
topLevelLayout->addWidget(lbFindWhat);
topLevelLayout->addWidget(edtFindStr);
QVBoxLayout *leftLayout = new QVBoxLayout;
leftLayout->addLayout(topLevelLayout);
leftLayout->addWidget(caseCheckBox);
leftLayout->addWidget(backwardCheckBox);
QVBoxLayout *rightLayout = new QVBoxLayout;
rightLayout->addWidget(btnFind);
rightLayout->addWidget(btnClose);
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 = edtFindStr->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) {
btnFind->setEnabled(!text.isEmpty());
}
但是在执行时,单击按钮btnSearch没有反应,而且报出“app没有槽btnSearchClick”(不是精确的错误信息,大意如此)。
我知道肯定是我的匹配“信号-槽”connect没有写对,即main中的“QObject::connect(btnSearch, SIGNAL(clicked), &app, SLOT(btnSearchClick()));”有问题。
在网上也找了很久,但没有解决问题。后来看到优快云上一个大侠(“shen_wei”)的一段话:“推荐你去看看Qt自带的例子。。这样你能学习的更多!!”,很有启发。找来找去,还是老老实实看Qt自带的例子吧。终于在“Examples\Qt-5.6\widgets\dialogs\findfiles”中找到答案。
只要把“QObject::connect(btnSearch, SIGNAL(clicked), &app, SLOT(btnSearchClick()));”修改下面的语句即可:
QObject::connect(btnSearch, &QAbstractButton::clicked, &app, &btnSearchClick);
也就是不使用SIGNAL和SLOT宏。
修改后,运行结果正确,正是我想要的结果。