[英]How can I change the timing for signals and slot in QT?
我正在创建一个管理学生信息的程序。 目前我有一个 tableview 和一个添加按钮,当我点击添加按钮时,会弹出一个新对话框,提示用户添加一个新学生。 我的意图是我创建一个信号和槽连接到我的对话框,这样每当按下 ok 按钮时,我的 tableview 就会刷新(我正在使用 SQLITE)。 但是,现在的问题是,在我看来,在我调用刷新窗口 function 后数据库正在更新,所以当我调用刷新窗口 function 时,数据库尚未更新。 我不确定这是否是问题所在,但这就是我的想法。
下面是一些代码: 当我点击添加按钮时
void viewStudents::on_addStudent_clicked()
{
studentWindow = new studentManagement(username,this);
QObject::connect(studentWindow,SIGNAL(accepted()),this, SLOT(refreshwindow()));
studentWindow->show();
}
我的刷新窗口 function
void viewStudents::refreshwindow()
{
QSqlQueryModel *modal = new QSqlQueryModel();
QSqlDatabase tempdb = QSqlDatabase::addDatabase("QSQLITE");
tempdb.setDatabaseName("accounts.db");
if(tempdb.open()){
QSqlQuery tempquery;
tempquery.exec("SELECT firstname, lastname, DOB, Day_of_lessons, Start_date, Price_per_lesson, Length_of_lessons from studentList WHERE teacher = '"+username+"';");
modal->setQuery(tempquery);
ui->tableView->setModel(modal);
ui->tableView->resizeColumnsToContents();
ui->tableView->resizeRowsToContents();
tempdb.close();
}
else{
QMessageBox::warning(this,"Error","Something unexpected has happened.");
}
}
我的添加学生对话框
studentManagement::studentManagement(QString username, QWidget *parent) :
QDialog(parent),
ui(new Ui::studentManagement)
{
this->username = username;
ui->setupUi(this);
QFont information_font = ui->informationLabel->font();
information_font.setPointSize(14);
information_font.setBold(true);
ui->informationLabel->setFont(information_font);
ui->startdate->setMinimumDate(QDate::currentDate());
ui->dayOfLessonsBox->addItem("Monday");
ui->dayOfLessonsBox->addItem("Tuesday");
ui->dayOfLessonsBox->addItem("Wednesday");
ui->dayOfLessonsBox->addItem("Thursday");
ui->dayOfLessonsBox->addItem("Friday");
ui->dayOfLessonsBox->addItem("Saturday");
ui->dayOfLessonsBox->addItem("Sunday");
}
studentManagement::~studentManagement()
{
delete ui;
}
void studentManagement::on_buttonBox_accepted()
{
QString firstname = ui->firstname->text();
QString lastname = ui->lastname->text();
QString DOB = ui->dateofbirth->text();
QString dayOfLessons = ui->dayOfLessonsBox->currentText();
QString startdate = ui->startdate->text();
QString pricing = ui->pricing->text();
QString lengthoflessons = ui->lengthoflessons->text();
QSqlDatabase mydb = QSqlDatabase::addDatabase("QSQLITE");
mydb.setDatabaseName("accounts.db");
if(!mydb.open())QMessageBox::warning(this,"File Not Found Error", "The database file cannot be find.");
else{
QSqlQuery query;
if(query.exec("INSERT INTO studentList VALUES('"+firstname+"', '"+lastname+"', '"+DOB+"', '"+dayOfLessons+"', '"+startdate+"', '"+pricing+"', '"+lengthoflessons+"', '"+username+"');")){
mydb.close();
}
}
}
如果有人能帮我一点忙,或者给我一些关于去哪里看的建议,我将不胜感激!
首先,您应该在构造函数中使用您的connect
语句,或者每次on_addStudent_clicked()
时都会执行一个新的连接,这不会形成错误,但完全没有必要。
其次,当我们向列表中添加一条记录时,我们希望确保立即刷新列表,因此它需要紧跟在insert
语句之后。
第三,Qt 非常智能,可以找到您要创建的隐式连接,如果您使用一般形式的on_something_someevent()
创建 function,那么它将自动查找名为something
的对象/类( QObject
类型)并连接它的信号是this
和someevent
on_something_someevent()
作为插槽的事件。 结果,像thisobject::on_something_someevent(){}
这样写 function 将自动呈现为:
QObject::connect(something, SIGNAL(someevent()), this, SLOT(on_something_someevent()));
这非常方便,但它可能会尝试创建不需要的connect
或至少引发警告或错误。
最后,不要忘记在您的 header 文件中使用public slot:
定义您的插槽。 公共部分是必要的,否则您会收到访问冲突错误,因为 Qt 框架无法调用您的插槽 function(来自另一个对象)。
这是您的代码的更正形式,我认为它可以完成这项工作(我没有您的 .ui 或 .h 文件,既没有您的两个类的完整源代码,也没有您的main()
function,所以请将其视为我希望传达要点的部分来源)
void viewStudents::refreshwindow()
{
QSqlQueryModel modal = QSqlQueryModel::QSqlQueryModel();
QSqlDatabase tempdb = QSqlDatabase::addDatabase("QSQLITE");
tempdb.setDatabaseName("accounts.db");
if (tempdb.open()) {
QSqlQuery tempquery;
tempquery.exec("SELECT firstname, lastname, DOB, Day_of_lessons, Start_date, Price_per_lesson, Length_of_lessons from studentList WHERE teacher = '" + username + "';");
modal->setQuery(tempquery);
ui->tableView->setModel(modal);
ui->tableView->resizeColumnsToContents();
ui->tableView->resizeRowsToContents();
tempdb.close();
}
else {
QMessageBox::warning(this, "Error", "Something unexpected has happened.");
}
}
studentManagement::studentManagement(QString username, QWidget *parent) :
QDialog(parent),
ui(new Ui::studentManagement)
{
this->username = username;
ui->setupUi(this);
QFont information_font = ui->informationLabel->font();
information_font.setPointSize(14);
information_font.setBold(true);
ui->informationLabel->setFont(information_font);
ui->startdate->setMinimumDate(QDate::currentDate());
ui->dayOfLessonsBox->addItem("Monday");
ui->dayOfLessonsBox->addItem("Tuesday");
ui->dayOfLessonsBox->addItem("Wednesday");
ui->dayOfLessonsBox->addItem("Thursday");
ui->dayOfLessonsBox->addItem("Friday");
ui->dayOfLessonsBox->addItem("Saturday");
ui->dayOfLessonsBox->addItem("Sunday");
// This connect statment could be quit unnecessary as Qt will create it automatically
// Since you have created the function name as it is expected by Qt (on_class_event)
QObject::connect(addStudent, SIGNAL(clicked()), this, SLOT(on_addStudent_clicked()));
}
studentManagement::~studentManagement()
{
delete ui;
}
void studentManagement::on_addStudent_clicked()
{
QString firstname = ui->firstname->text();
QString lastname = ui->lastname->text();
QString DOB = ui->dateofbirth->text();
QString dayOfLessons = ui->dayOfLessonsBox->currentText();
QString startdate = ui->startdate->text();
QString pricing = ui->pricing->text();
QString lengthoflessons = ui->lengthoflessons->text();
QSqlDatabase mydb = QSqlDatabase::addDatabase("QSQLITE");
mydb.setDatabaseName("accounts.db");
if (!mydb.open())
{
QMessageBox::warning(this, "File Not Found Error", "The database file cannot be find.");
}
else
{
QSqlQuery query;
if (query.exec("INSERT INTO studentList VALUES('" + firstname + "', '" + lastname + "', '" + DOB + "', '" + dayOfLessons + "', '" + startdate + "', '" + pricing + "', '" + lengthoflessons + "', '" + username + "');"))
mydb.close();
}
studentWindow = new studentManagement(username, this);
studentWindow->show();
viewStudents::refreshwindow();
// OR
// define refreshwindow as a public slot and emit a signal from here
emit(viewStudents::refreshwindow());
}
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