Qt——Common properties, methods and signals of QLineEdit control

Common properties, methods and signals of QLineEdit control

1. Common properties and methods of QLineEdit control
2. Common signals of QLineEdit control

QLineEdit: Single-line text input box control

1. Commonly used properties and methods of QLineEdit control:

1. text：

Description: Get or set the text content in the text box.
Usage: You can use setText()the method to set the text content of the text box, or use the text() method to get the current text in the text box.

setText(const QString &text)：

2. placeholderText：

Description: Set a placeholder text, displayed when the text box is empty, to prompt the user to enter the expected content.
Usage: Use setPlaceholderText()the method to set placeholder text, usually used to indicate what content the user should input.

setPlaceholderText(const QString &text)：

edt->setPlaceholderText("请输入密码")://提示输入文本

3. maxLength：

Description: Set the maximum number of characters allowed to be entered in the text box. Usage: Set the maximum character limit
through the method, which is useful for limiting the length of user input.setMaxLength()

setMaxLength(int length)：

4. echoMode：

Description: Set the text display mode, used to handle the input of sensitive information such as passwords.
Usage: Use setEchoMode()the method to set the display mode, you can choose to display normal text, password characters or not display.

setEchoMode(EchoMode mode)：

edt->setEchoMode(QLineEdit::Password); //设置密码隐藏模式

edt->setEchoMode(QLineEdit::PasswordEchoOnEdit): //设置鼠标点击别的地方密码隐藏模式

5. readOnly：

Description: Set whether the text box is in read-only mode, that is, users cannot edit the content.
Usage: Use setReadOnly()the method to set whether it is read-only, suitable for scenarios where information is displayed but editing is not allowed.

setReadOnly(bool readOnly)：

6. selectedText(): Get the text data selected by the cursor

edt->selectedText();

2. Common signals of QLineEdit control

1. textChanged(const QString &text)：

Description: This signal is triggered when the text content changes.
Parameters: text is the current text content.
Usage: Connect to the slot function of this signal to perform corresponding operations when the text changes.

2. editingFinished()：

Description: This signal is triggered when editing is completed (for example, the user presses the Enter key).
Usage: Connect to the slot function of this signal to perform corresponding operations when editing is completed.

3. returnPressed()：

Description: This signal is triggered when the user presses the Enter key.
Usage: Connect to the slot function of this signal to perform the corresponding operation when the user presses the Enter key.

4. cursorPositionChanged(int oldPos, int newPos)：

Description: This signal is triggered when the cursor position changes.
Parameters: oldPos is the cursor position before change, newPos is the cursor position after change.
Usage: Connect to the slot function of this signal to perform corresponding operations when the cursor position changes.

5. selectionChanged()：

Description: This signal is triggered when the selected text changes.
Usage: Connect to the slot function of this signal to perform corresponding operations when the selected text changes.

6. textEdited(const QString &text)：

Description: This signal is triggered when the text content is edited (not necessarily changed).
Parameters: text is the current text content.
Usage: Connect to the slot function of this signal to perform corresponding operations when the text is edited.

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    
    
    ui->setupUi(this);
    setFixedSize(640,480);
    lab = new QLabel("行编辑器", this);

//    ed1 = new QLineEdit(QLine(), this);
//    ed1->setFixedSize(100, 50);

    //setEchoMode(QLineEdit::Password):设置密码隐藏模式
    ui->etd1->setEchoMode(QLineEdit::Password);
    //setEchoMode(QLineEdit::PasswordEchoOnEdit):设置鼠标点击别的地方密码隐藏模式
    ui->etd2->setEchoMode(QLineEdit::PasswordEchoOnEdit);

    //setPlaceholderText():提示输入文本
    ui->etd3->setPlaceholderText("密码");

    //绑定事件（信号发送者, 触发事件地址, 信号接收者, 触发事件槽函数）
    connect(ui->etd, &QLineEdit::editingFinished, this, &Widget::textFinshed);
    //
    //connect(ui->etd2, &QLineEdit:: textChanged, this, QOverload<QString>::of(&Widget::te));



}

Widget::~Widget()
{
    
    
    delete ui;
}

void Widget::textFinshed()
{
    
    
    ui->label->setText(ui->etd->text());
}

/*
 * 设计器右键转到槽：自动声明定义槽函数，该函数已经绑定了信号
 * 槽函数语法：void on_objectName_signal();
 * on_objectName控件的signal信号被触发，系统自动调用该槽函数
 */

void Widget::on_etd1_selectionChanged() //on_对象名_信号()
{
    
    
    //selectedText():获得光标选中的文本数据
    ui->label_2->setText(ui->etd1->selectedText());
}

/*
 * 当信号有形参，目的是触发信号时，传递数据。关联的槽函数，如果需要接收数据，则必须设计 同类型的形爹，如果不需要数据，则不必设置形参
 * 信号与槽函数的参数个数关系: 槽函数形参个数 <= 信号的形参个数
 */

void Widget::on_etd2_textChanged()
{
    
    
    ui->label_3->setText(ui->etd2->text());
}


void Widget::on_etd2_textChanged(const QString text)
{
    
    
    ui->label_3->setText(text);
}