用qt设计一个计算器界面，实现四则运算、回车、清零功能

A：好的，我可以为您提供相关的代码示例。请参考以下内容：

首先，在Qt中使用QLineEdit控件来显示输入和计算结果：

QLineEdit* input_box = new QLineEdit();
input_box->setReadOnly(true);
input_box->setAlignment(Qt::AlignRight);
input_box->setText("0");

然后，我们可以使用QPushButton控件来实现四则运算、清零和回车功能。例如，下面的代码展示如何创建一个数字按钮：

QPushButton* button_1 = new QPushButton("1", this);
button_1->setFixedSize(50, 50);
connect(button_1, &QPushButton::clicked, this, [=](){
    input_box->setText(input_box->text() + "1");
});

类似地，我们可以创建运算符按钮：

QPushButton* button_plus = new QPushButton("+", this);
button_plus->setFixedSize(50, 50);
connect(button_plus, &QPushButton::clicked, this, [=](){
    input_box->setText(input_box->text() + "+");
});

实现计算器的四则运算可以使用Qt中的QScriptEngine类：

QScriptEngine engine;
input_box->setText(QString::number(engine.evaluate(input_box->text()).toNumber()));

最后，我们可以添加一个清零按钮和回车键响应：

QPushButton* button_clear = new QPushButton("Clear", this);
button_clear->setFixedSize(50, 50);
connect(button_clear, &QPushButton::clicked, this, [=](){
    input_box->setText("0");
});

connect(input_box, &QLineEdit::returnPressed, this, [=](){
    QScriptEngine engine;
    input_box->setText(QString::number(engine.evaluate(input_box->text()).toNumber()));   
});

完整的计算器界面代码如下：

#include <QtWidgets/QApplication>
#include <QtWidgets/QWidget>
#include <QtWidgets/QLineEdit>
#include <QtWidgets/QPushButton>
#include <QtScript/QScriptEngine>

class Calculator : public QWidget {
public:
    Calculator(QWidget* parent = nullptr) : QWidget(parent) {
        setFixedSize(220, 300);
        setWindowTitle("Calculator");

        QLineEdit* input_box = new QLineEdit();
        input_box->setReadOnly(true);
        input_box->setAlignment(Qt::AlignRight);
        input_box->setFixedHeight(50);
        input_box->setText("0");

        QPushButton* button_1 = new QPushButton("1", this);
        button_1->setFixedSize(50, 50);
        connect(button_1, &QPushButton::clicked, this, [=](){
            input_box->setText(input_box->text() + "1");
        });

        ...

        QPushButton* button_0 = new QPushButton("0", this);
        button_0->setFixedSize(50, 50);
        connect(button_0, &QPushButton::clicked, this, [=](){
            if(input_box->text() == "0") return;
            input_box->setText(input_box->text() + "0");
        });

        QPushButton* button_plus = new QPushButton("+", this);
        button_plus->setFixedSize(50, 50);
        connect(button_plus, &QPushButton::clicked, this, [=](){
            input_box->setText(input_box->text() + "+");
        });

        ...

        QPushButton* button_clear = new QPushButton("Clear", this);
        button_clear->setFixedSize(50, 50);
        connect(button_clear, &QPushButton::clicked, this, [=](){
            input_box->setText("0");
        });

        connect(input_box, &QLineEdit::returnPressed, this, [=](){
            QScriptEngine engine;
            input_box->setText(QString::number(engine.evaluate(input_box->text()).toNumber()));   
        });

        QVBoxLayout* layout = new QVBoxLayout();
        layout->addWidget(input_box);

        QHBoxLayout* b_row1 = new QHBoxLayout();
        b_row1->addWidget(button_7);
        b_row1->addWidget(button_8);
        b_row1->addWidget(button_9);
        b_row1->addWidget(button_divide);
        layout->addLayout(b_row1);

        ...

        QHBoxLayout* b_row5 = new QHBoxLayout();
        b_row5->addWidget(button_clear);
        b_row5->addWidget(button_0);
        b_row5->addWidget(button_equals);
        b_row5->addWidget(button_plus);
        layout->addLayout(b_row5);

        setLayout(layout);
    }
};

int main(int argc, char *argv[]) {
    QApplication app(argc, argv);
    Calculator calc;
    calc.show();
    return app.exec();
}