QT qlineedit, qtextedit, qplaintextedit differences

QLineEdit、QTextEdit 、QPlainTextEdit Respective use scenarios

QLineEdit

QLineEdit It's a single line text input box .

QLineEdit Allows users to enter and edit single line plain text , Provides a lot of useful editing functions , Include ： Undo and Redo 、 Cut and paste 、 And drag and drop （ see setDragEnabled()）.

By changing the echoMode(), It can also be set as a “ Just write ” Field , Used to enter passwords, etc .

// Limit maximum input  128  position 
lineEdit->setMaxLength(128);
// Not writable 
lineEdit->setEchoMode(QLineEdit::NoEcho);
// password * Number input 
lineEdit->setEchoMode(QLineEdit::Password);

  Varied echoMode()

    switch (index) {
        case 0:
            // Default , What you enter is displayed 
            echoLineEdit->setEchoMode(QLineEdit::Normal);
            break;
        case 1:
            // password , Generally, small black dots are used to cover the characters you enter 
            echoLineEdit->setEchoMode(QLineEdit::Password);
            break;
        case 2:
            // When editing, input characters to display the input content , Otherwise, use small black dots instead 
            echoLineEdit->setEchoMode(QLineEdit::PasswordEchoOnEdit);
            break;
        case 3:
            // No input is visible （ Just can't see , It's not that you can't input ）
            echoLineEdit->setEchoMode(QLineEdit::NoEcho);
        }

 LineEdit Edit box limits number input collation

// Display the integer of the specified range 
ui->lineEdit->setValidator(new QIntValidator(1,1000,this));  // [1,1000] Integer input in the range 
ui->lineEdit->setValidator(new QDoubleValidator(0.1,0.9,2,this)); // [0.1,0.9], After the decimal point 2 position 
ui->lineEdit->setValidator(new QRegularExpressionValidator(QRegularExpression("^[(\\s|\\S)+]{0,200}$"),this)); //  Input 200 Characters 


// Just enter the numbers , Decimal point and minus sign 
QRegExp exp("[0-9\\.-]+$");
QValidator *Validator = new QRegExpValidator(exp);
ui->lineEdit->setValidator(Validator);

//ip Address input 
QString exp = "^(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|[1-9])\\."
          "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)\\."
          "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)\\."
          "(1\\d{2}|2[0-4]\\d|25[0-5]|[1-9]\\d|\\d)$";
QRegExp rege(exp);
QValidator *Validator = new QRegExpValidator(rege);
ui->lineEdit->setValidator(Validator);

You can only enter Numbers

     // Integers 
     QRegExp exp("^-?[0-9]+$");
     QValidator *Validator = new QRegExpValidator(exp);
     ui->lineEdit_PageIndexList->setValidator(Validator);

data

// The set of real Numbers 
QRegExp exp("^-?[0-9\\.]+$");
QValidator *Validator = new QRegExpValidator(exp);
ui->lineEdit->setValidator(Validator);
 
// Positive integer 
QRegExp exp("^0?[.]\\d+$");
QValidator *Validator = new QRegExpValidator(exp);
ui->lineEdit->setValidator(Validator);
 
// Positive decimal 
QRegExp exp("^[1-9]\\d+$");
QValidator *Validator = new QRegExpValidator(exp);
ui->lineEdit->setValidator(Validator);

QTextEdit

Multiple lines , Rich text editor , It can also be displayed HTML Rich text ;

QTextEdit* m_textShower;// The text that reads the contents of the file is displayed 

m_textShower = newQTextEdit;

(1) How to set the font 
QFonttextFont;

textFont.setPointSize(16);

m_textShower->setFont(textFont);

(2) Set the method of editing as read-only property 
m_textShower->setReadOnly(true);

(3) How to set text 

QTextCursorcsor = m_textShower->textCursor();

csor.movePosition(QTextCursor::Start);

csor.insertText(fileContext);

(4) How to clear text 
m_textShower->clear();

Text can use setSelection() or selectAll() To select , The selected text can be cut()、copy() and paste(), Use setAlignment() To set the alignment of text .

Very powerful ;

QPlainTextEdit

QPlainTextEdit Is a multiline text editor , For displaying and editing multiple lines of simple text .

QPlainTextEdit It can be understood as QTextEdit Low profile version of .QPlainTextEdit Support plain text display ,QTextEdit Support rich text display . One more style .
QPlainTextEdit The displayed efficiency ratio QTextEdit high , If you need to display a lot of text , Especially when you need the scroll bar to scroll back and forth ,QPlainTextEdit Is much better .

Common methods

// Append a line of string 
appendPlainText()
// take QPlainTextEdit The text in the component is converted to a string 
toPlainText()

// Reading strings line by line is troublesome ,QPlainTextEidt With QTextDocument Type stores data 
document() Member functions , You can return the file object pointer QTextDocument
// Is a text object in memory , Store in text blocks , Judge the text block with carriage return , That is to say, generally one line is a text block 
QTextDocument
//QTextDocument Member function of , Read text block , The serial number from 0 Start , The read text block is QTextBlock type , You can go through text() Member function gets text QString

findBlockByNumber(int)
// Member functions , Can get QTextDocument Number of text blocks , Used to traverse text blocks 
blockCount()