QlineEdit信号映射问题

Question

我想把参数传递给slot。所以我使用信号映射。我使用setmapping将QlinEedit变量作为参数传递给插槽。但是我的槽函数没有调用。

QSignalMapper* maper = new QSignalMapper (this) ;
connect(ui->step2,SIGNAL(returnPressed()),maper,SLOT(map()));
maper->setMapping(ui->step2,ui->step2);
connect (maper, SIGNAL(mapped(QLineEdit*)), this, SLOT(on_steps_returnPressed(QLineEdit*))) ;

Answer 1

QSignalMapper类已被弃用，您应该将新的信号/槽语法与lambda函数一起使用：

connect(ui->step2, &QLineEdit::returnPressed, [=]() { this->on_steps_returnPressed(ui->step2); });

您还可以仅传递QLineEdit中的文本，而不是其上的指针：

connect(ui->step2, &QLineEdit::returnPressed, [=]() { this->on_steps_returnPressed(ui->step2->text()); });

如果无论如何都要使用QSignalMapper，那么就必须使用信号QSignalMapper::mapped(QWidget*)。由于插槽必须与连接的信号具有相同的签名，因此on_steps_returnPressed变为on_steps_returnPressed(QWidget*) (将参数转换为QLineEdit)：

QSignalMapper* maper = new QSignalMapper (this) ;
connect(step2, SIGNAL(returnPressed()), maper, SLOT(map()));
maper->setMapping(step2, step2);
connect(maper, SIGNAL(mapped(QWidget*)), this, SLOT(on_steps_returnPressed(QWidget*)));

你的槽应该是这样的：

void on_steps_returnPressed(QWidget* widget)
{
    QLineEdit* edit = qobject_cast<QLineEdit*>(widget);
    if (!edit)
        return;
    label->setText(edit->text());
}

比较这两种解决方案的完整示例：

class Widget: public QWidget
{
    Q_OBJECT
public:
    Widget(QWidget* parent=nullptr): QWidget(parent),
        lineEdit1(new QLineEdit(this)),
        lineEdit2(new QLineEdit(this)),
        label(new QLabel(this))
    {
        QVBoxLayout* layout = new QVBoxLayout(this);
        layout->addWidget(lineEdit1);
        layout->addWidget(lineEdit2);
        layout->addWidget(label);

        connect(lineEdit1, &QLineEdit::returnPressed, [=]() { this->on_steps_returnPressed(lineEdit1); });

        QSignalMapper* maper = new QSignalMapper (this) ;
        connect(lineEdit2, SIGNAL(returnPressed()), maper, SLOT(map()));
        maper->setMapping(lineEdit2, lineEdit2);
        connect(maper, SIGNAL(mapped(QWidget*)), this, SLOT(on_steps_returnPressed(QWidget*)));
    }

public slots:
    void on_steps_returnPressed(QLineEdit* edit)
    {
        label->setText(edit->text());
    }
    void on_steps_returnPressed(QWidget* widget)
    {
        QLineEdit* edit = qobject_cast<QLineEdit*>(widget);
        if (!edit)
            return;
        label->setText(edit->text());
    }
private:
    QLineEdit* lineEdit1;
    QLineEdit* lineEdit2;
    QLabel* label;
};