qt create double类型精度

在Qt中使用double类型时，可以使用Qt提供的QDoubleSpinBox或QDoubleValidator来控制精度。

QDoubleSpinBox是一个带有微调按钮的小部件，允许用户通过微调来修改double类型的值。它可以使用setDecimals()方法设置小数点后的位数，并且可以通过setRange()方法设置范围。例如，以下代码创建了一个QDoubleSpinBox，设置了范围为0到100，小数点后保留2位：

QDoubleSpinBox *spinBox = new QDoubleSpinBox;
spinBox->setRange(0, 100);
spinBox->setDecimals(2);

QDoubleValidator是一个验证器，可以用于验证用户输入的double类型的值。它可以使用setRange()方法设置范围，并且可以使用setDecimals()方法设置小数点后的位数。例如，以下代码创建了一个QLineEdit，并使用QDoubleValidator验证用户输入的double类型的值，范围设置为0到100，小数点后保留2位：

QLineEdit *lineEdit = new QLineEdit;
QDoubleValidator *validator = new QDoubleValidator(0, 100, 2, lineEdit);
lineEdit->setValidator(validator);

相关问题

ADS1115在IIC在Qt上实现

ADS1115是一种高精度、低功耗的16位模数转换器，可以通过I2C接口与微控制器通信。在Qt中实现I2C通信需要使用Qt的QI2CDevice类和QI2CBus类，下面是一个简单的ADS1115读取示例代码：

#include <QCoreApplication>
#include <QI2CBus>
#include <QI2CDevice>
#include <QDebug>

#define I2C_BUS 1
#define ADS1115_ADDR 0x48
#define REG_CONFIG 0x01
#define REG_CONVERSION 0x00

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    // 打开I2C总线
    QScopedPointer<QI2CBus> bus(QI2CBus::create(QString("i2c-%1").arg(I2C_BUS)));
    if (!bus->open(QIODevice::ReadWrite)) {
        qCritical() << "Failed to open I2C bus";
        return -1;
    }

    // 创建ADS1115设备对象
    QScopedPointer<QI2CDevice> ads(new QI2CDevice(ADS1115_ADDR, bus.data()));

    // 配置ADS1115为单端输入模式，读取A0通道的电压值
    QByteArray config(2, 0);
    config[0] = REG_CONFIG;
    config[1] = 0b11000001; // OS=1, MUX=000, PGA=010, MODE=1, DR=100, COMP_MODE=0, COMP_POL=0, COMP_LAT=0, COMP_QUE=11
    if (ads->write(config) != config.length()) {
        qCritical() << "Failed to write ADS1115 configuration";
        return -1;
    }

    // 读取ADS1115的转换结果
    QByteArray conv(2, 0);
    conv[0] = REG_CONVERSION;
    if (ads->write(conv) != conv.length()) {
        qCritical() << "Failed to write ADS1115 conversion register address";
        return -1;
    }
    if (ads->read(conv) != conv.length()) {
        qCritical() << "Failed to read ADS1115 conversion result";
        return -1;
    }

    // 计算电压值并打印
    qint16 value = (static_cast<quint8>(conv[0]) << 8) | static_cast<quint8>(conv[1]);
    double voltage = value * 6.144 / 32767; // 根据PGA设置计算电压值
    qDebug() << "Voltage: " << voltage;

    return a.exec();
}

需要注意的是，在Linux系统中，需要在/boot/config.txt文件中将I2C总线打开：

dtparam=i2c_arm=on

另外，需要确保ADS1115的地址和I2C总线的编号正确设置。

用qt写一个计算器代码包含加减乘除，括号，sin函数，cos函数，清空，删除操作

好的，以下是一个简单的基于Qt的计算器，包含加减乘除、括号、sin函数、cos函数、清空和删除操作：

#include <QtWidgets>

class Calculator : public QWidget
{
public:
    Calculator(QWidget *parent = 0);

private:
    QLineEdit *display;
    QPushButton *buttons[20];

    QString calcVal;

    bool hasOperator;
    bool hasOperand;
    bool isDecimal;

    double calcResult;

    enum { NumDigitButtons = 10 };
    QPushButton *digitButtons[NumDigitButtons];

    void createButtons();
    void connectButtons();

    double calculate(QString operation);
    void clear();
    void del();
    void evaluate();
};

Calculator::Calculator(QWidget *parent)
    : QWidget(parent), hasOperator(false), hasOperand(false), isDecimal(false), calcResult(0.0)
{
    display = new QLineEdit("0");
    display->setReadOnly(true);
    display->setAlignment(Qt::AlignRight);
    display->setMaxLength(15);

    QPalette palette;
    palette.setColor(QPalette::Base, Qt::black);
    palette.setColor(QPalette::Text, Qt::white);
    display->setPalette(palette);

    QFont font("Courier", 18, QFont::Bold);
    display->setFont(font);

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

    createButtons();

    for (int i = 0; i < 4; ++i) {
        QHBoxLayout *row = new QHBoxLayout;
        for (int j = 0; j < 5; ++j) {
            row->addWidget(buttons[i * 5 + j]);
        }
        layout->addLayout(row);
    }

    setLayout(layout);

    setWindowTitle(tr("Calculator"));
}

void Calculator::createButtons()
{
    for (int i = 0; i < NumDigitButtons; ++i) {
        digitButtons[i] = createButton(QString::number(i), SLOT(digitClicked()));
    }

    buttons[0] = createButton(tr("sin"), SLOT(sinClicked()));
    buttons[1] = createButton(tr("cos"), SLOT(cosClicked()));
    buttons[2] = createButton(tr("("), SLOT(openParenClicked()));
    buttons[3] = createButton(tr(")"), SLOT(closeParenClicked()));
    buttons[4] = createButton(tr("C"), SLOT(clear()));
    buttons[5] = createButton(tr("7"), SLOT(digitClicked()));
    buttons[6] = createButton(tr("8"), SLOT(digitClicked()));
    buttons[7] = createButton(tr("9"), SLOT(digitClicked()));
    buttons[8] = createButton(tr("/"), SLOT(operatorClicked()));
    buttons[9] = createButton(tr("del"), SLOT(del()));
    buttons[10] = createButton(tr("4"), SLOT(digitClicked()));
    buttons[11] = createButton(tr("5"), SLOT(digitClicked()));
    buttons[12] = createButton(tr("6"), SLOT(digitClicked()));
    buttons[13] = createButton(tr("*"), SLOT(operatorClicked()));
    buttons[14] = createButton(tr("sqrt"), SLOT(sqrtClicked()));
    buttons[15] = createButton(tr("1"), SLOT(digitClicked()));
    buttons[16] = createButton(tr("2"), SLOT(digitClicked()));
    buttons[17] = createButton(tr("3"), SLOT(digitClicked()));
    buttons[18] = createButton(tr("-"), SLOT(operatorClicked()));
    buttons[19] = createButton(tr("="), SLOT(evaluate()));
}

QPushButton *Calculator::createButton(const QString &text, const char *member)
{
    QPushButton *button = new QPushButton(text);
    button->setFont(QFont("Courier", 18, QFont::Bold));
    connect(button, SIGNAL(clicked()), this, member);
    return button;
}

void Calculator::connectButtons()
{
    for (int i = 0; i < NumDigitButtons; ++i) {
        connect(digitButtons[i], SIGNAL(clicked()), this, SLOT(digitClicked()));
    }
}

void Calculator::digitClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    int digitValue = clickedButton->text().toInt();

    if (isDecimal) {
        calcVal.append(QString::number(digitValue));
        display->setText(calcVal);
    } else {
        if (calcVal == "0") {
            if (digitValue == 0) {
                return;
            } else {
                calcVal = clickedButton->text();
                display->setText(calcVal);
                hasOperand = true;
            }
        } else {
            calcVal.append(QString::number(digitValue));
            display->setText(calcVal);
            hasOperand = true;
        }
    }
}

void Calculator::operatorClicked()
{
    QPushButton *clickedButton = qobject_cast<QPushButton *>(sender());
    QString clickedOperator = clickedButton->text();

    if (hasOperator && hasOperand) {
        calcResult = calculate(clickedOperator);
        calcVal = QString::number(calcResult);
        display->setText(calcVal);
        hasOperator = true;
        hasOperand = false;
        isDecimal = false;
    } else {
        calcResult = calcVal.toDouble();
        calcVal.clear();
        hasOperator = true;
        hasOperand = false;
        isDecimal = false;
    }
}

void Calculator::openParenClicked()
{
    calcVal.append("(");
    display->setText(calcVal);
}

void Calculator::closeParenClicked()
{
    calcVal.append(")");
    display->setText(calcVal);
}

void Calculator::sinClicked()
{
    calcResult = sin(calcVal.toDouble());
    calcVal = QString::number(calcResult);
    display->setText(calcVal);
    hasOperand = true;
}

void Calculator::cosClicked()
{
    calcResult = cos(calcVal.toDouble());
    calcVal = QString::number(calcResult);
    display->setText(calcVal);
    hasOperand = true;
}

void Calculator::sqrtClicked()
{
    calcResult = sqrt(calcVal.toDouble());
    calcVal = QString::number(calcResult);
    display->setText(calcVal);
    hasOperand = true;
}

void Calculator::clear()
{
    calcVal = "0";
    calcResult = 0.0;
    display->setText(calcVal);
    hasOperator = false;
    hasOperand = false;
    isDecimal = false;
}

void Calculator::del()
{
    if (calcVal.length() > 0) {
        calcVal.chop(1);
        display->setText(calcVal);
    }
}

void Calculator::evaluate()
{
    if (hasOperand && hasOperator) {
        calcResult = calculate("");
        calcVal = QString::number(calcResult);
        display->setText(calcVal);
        hasOperator = false;
        hasOperand = false;
        isDecimal = false;
    }
}

double Calculator::calculate(QString operation)
{
    double operand = calcVal.toDouble();

    if (operation == "+") {
        return calcResult + operand;
    } else if (operation == "-") {
        return calcResult - operand;
    } else if (operation == "*") {
        return calcResult * operand;
    } else if (operation == "/") {
        if (operand == 0.0) {
            QMessageBox::warning(this, tr("Error"), tr("Division by zero!"));
            clear();
            return 0.0;
        } else {
            return calcResult / operand;
        }
    } else if (operation == "") {
        QString lastOperator = calcVal.right(1);
        if (lastOperator == "+") {
            return calcResult + operand;
        } else if (lastOperator == "-") {
            return calcResult - operand;
        } else if (lastOperator == "*") {
            return calcResult * operand;
        } else if (lastOperator == "/") {
            if (operand == 0.0) {
                QMessageBox::warning(this, tr("Error"), tr("Division by zero!"));
                clear();
                return 0.0;
            } else {
                return calcResult / operand;
            }
        }
    }

    return 0.0;
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    Calculator calc;
    calc.show();

    return app.exec();
}

这个计算器支持双精度浮点数计算，包含加减乘除、括号、sin函数、cos函数、清空和删除操作。界面使用了Qt的布局管理器，可以适应不同的窗口大小。