QLineEdit Class Reference
^{[QtGui module]}

Detailed Description

The QLineEdit widget is a one-line text editor.

A line edit allows the user to enter and edit a single line of plain text with a useful collection of editing functions, including undo and redo, cut and paste, and drag and drop.

By changing the echoMode() of a line edit, it can also be used as a "write-only" field, for inputs such as passwords.

The length of the text can be constrained to maxLength(). The text can be arbitrarily constrained using a validator() or an inputMask(), or both.

A related class is QTextEdit which allows multi-line, rich text editing.

You can change the text with setText() or insert(). The text is retrieved with text(); the displayed text (which may be different, see EchoMode) is retrieved with displayText(). Text can be selected with setSelection() or selectAll(), and the selection can be cut(), copy()ied and paste()d. The text can be aligned with setAlignment().

When the text changes the textChanged() signal is emitted; when the text changes other than by calling setText() the textEdited() signal is emitted; when the cursor is moved the cursorPositionChanged() signal is emitted; and when the Return or Enter key is pressed the returnPressed() signal is emitted.

When editing is finished, either because the line edit lost focus or Return/Enter is pressed the editingFinished() signal is emitted.

Note that if there is a validator set on the line edit, the returnPressed()/editingFinished() signals will only be emitted if the validator returns QValidator::Acceptable.

By default, QLineEdits have a frame as specified by the Windows and Motif style guides; you can turn it off by calling setFrame(false).

The default key bindings are described below. The line edit also provides a context menu (usually invoked by a right mouse click) that presents some of these editing options.

Any other key sequence that represents a valid character, will cause the character to be inserted into the line edit.

See also QTextEdit, QLabel, QComboBox, and GUI Design Handbook: Field, Entry.

Member Type Documentation

enum QLineEdit::EchoMode

This enum type describes how a line edit should display its contents.

See also setEchoMode() and echoMode().

Property Documentation

acceptableInput : const bool

This property holds whether the input satisfies the inputMask and the validator.

Access functions:

• bool hasAcceptableInput () const

See also setInputMask() and setValidator().

alignment : Qt::Alignment

This property holds the alignment of the line edit.

Only horizontal alignments are allowed in here, Qt::AlignJustify will map to Qt::AlignLeft.

Access functions:

• Qt::Alignment alignment () const
• void setAlignment ( Qt::Alignment flag )

See also Qt::Alignment.

cursorPosition : int

This property holds the current cursor position for this line edit.

Setting the cursor position causes a repaint when appropriate.

Access functions:

• int cursorPosition () const
• void setCursorPosition ( int )

displayText : const QString

This property holds the displayed text.

If echoMode is Normal this returns the same as text(); if EchoMode is Password it returns a string of asterisks text().length() characters long, e.g. "******"; if EchoMode is NoEcho returns an empty string, "".

Access functions:

• QString displayText () const

See also setEchoMode(), text(), and EchoMode.

dragEnabled : bool

This property holds whether the lineedit starts a drag if the user presses and moves the mouse on some selected text.

Dragging is disabled by default.

Access functions:

• bool dragEnabled () const
• void setDragEnabled ( bool b )

echoMode : EchoMode

This property holds the line edit's echo mode.

The initial setting is Normal, but QLineEdit also supports NoEcho and Password modes.

The widget's display and the ability to copy or drag the text is affected by this setting.

Access functions:

• EchoMode echoMode () const
• void setEchoMode ( EchoMode )

See also EchoMode and displayText().

frame : bool

This property holds whether the line edit draws itself with a frame.

If enabled (the default) the line edit draws itself inside a frame, otherwise the line edit draws itself without any frame.

Access functions:

• bool hasFrame () const
• void setFrame ( bool )

hasSelectedText : const bool

This property holds whether there is any text selected.

hasSelectedText() returns true if some or all of the text has been selected by the user; otherwise returns false.

Access functions:

• bool hasSelectedText () const

See also selectedText().

inputMask : QString

This property holds the validation input mask.

If no mask is set, inputMask() returns an empty string.

Sets the QLineEdit's validation mask. Validators can be used instead of, or in conjunction with masks; see setValidator().

Unset the mask and return to normal QLineEdit operation by passing an empty string ("") or just calling setInputMask() with no arguments.

The mask format understands these mask characters:

The mask consists of a string of mask characters and separators, optionally followed by a semicolon and the character used for blanks: the blank characters are always removed from the text after editing. The default blank character is space.

Examples:

To get range control (e.g. for an IP address) use masks together with validators.

Access functions:

• QString inputMask () const
• void setInputMask ( const QString & inputMask )

See also maxLength.

maxLength : int

This property holds the maximum permitted length of the text.

If the text is too long, it is truncated at the limit.

If truncation occurs any selected text will be unselected, the cursor position is set to 0 and the first part of the string is shown.

If the line edit has an input mask, the mask defines the maximum string length.

Access functions:

• int maxLength () const
• void setMaxLength ( int )

See also inputMask.

modified : bool

This property holds whether the line edit's contents has been modified by the user.

The modified flag is never read by QLineEdit; it has a default value of false and is changed to true whenever the user changes the line edit's contents.

This is useful for things that need to provide a default value but do not start out knowing what the default should be (perhaps it depends on other fields on the form). Start the line edit without the best default, and when the default is known, if modified() returns false (the user hasn't entered any text), insert the default value.

Calling setText() resets the modified flag to false.

Access functions:

• bool isModified () const
• void setModified ( bool )

readOnly : bool

This property holds whether the line edit is read only.

In read-only mode, the user can still copy the text to the clipboard, or drag and drop the text (if echoMode() is Normal), but cannot edit it.

QLineEdit does not show a cursor in read-only mode.

Access functions:

• bool isReadOnly () const
• void setReadOnly ( bool )

See also setEnabled().

redoAvailable : const bool

This property holds whether redo is available.

Access functions:

• bool isRedoAvailable () const

selectedText : const QString

This property holds the selected text.

If there is no selected text this property's value is an empty string.

Access functions:

• QString selectedText () const

See also hasSelectedText().

text : QString

This property holds the line edit's text.

Setting this property clears the selection, clears the undo/redo history, moves the cursor to the end of the line and resets the modified property to false. The text is not validated when inserted with setText().

The text is truncated to maxLength() length.

Access functions:

• QString text () const
• void setText ( const QString & )

See also insert() and clear().

undoAvailable : const bool

This property holds whether undo is available.

Access functions:

• bool isUndoAvailable () const

Member Function Documentation

QLineEdit::QLineEdit ( QWidget * parent = 0 )

Constructs a line edit with no text.

The maximum text length is set to 32767 characters.

The parent argument is sent to the QWidget constructor.

See also setText() and setMaxLength().

QLineEdit::QLineEdit ( const QString & contents, QWidget * parent = 0 )

Constructs a line edit containing the text contents.

The cursor position is set to the end of the line and the maximum text length to 32767 characters.

The parent and argument is sent to the QWidget constructor.

See also text() and setMaxLength().

QLineEdit::~QLineEdit ()

Destroys the line edit.

void QLineEdit::backspace ()

If no text is selected, deletes the character to the left of the text cursor and moves the cursor one position to the left. If any text is selected, the cursor is moved to the beginning of the selected text and the selected text is deleted.

See also del().

void QLineEdit::clear ()   [slot]

Clears the contents of the line edit.

See also setText() and insert().

void QLineEdit::contextMenuEvent ( QContextMenuEvent * event )   [virtual protected]

Shows the standard context menu created with createStandardContextMenu().

If you do not want the line edit to have a context menu, you can set its contextMenuPolicy to Qt::NoContextMenu. If you want to customize the context menu, reimplement this function. If you want to extend the standard context menu, reimplement this function, call createStandardContextMenu() and extend the menu returned.

    void LineEdit::contextMenuEvent(QContextMenuEvent *event)
    {
        QMenu *menu = createStandardContextMenu();
        menu->addAction(tr("My Menu Item"));
        //...
        menu->exec(event->globalPos());
        delete menu;
    }

The event parameter is used to obtain the position where the mouse cursor was when the event was generated.

Reimplemented from QWidget.

See also setContextMenuPolicy().

void QLineEdit::copy () const   [slot]

Copies the selected text to the clipboard, if there is any, and if echoMode() is Normal.

See also cut() and paste().

QMenu * QLineEdit::createStandardContextMenu ()

This function creates the standard context menu which is shown when the user clicks on the line edit with the right mouse button. It is called from the default contextMenuEvent() handler. The popup menu's ownership is transferred to the caller.

void QLineEdit::cursorBackward ( bool mark, int steps = 1 )

Moves the cursor back steps characters. If mark is true each character moved over is added to the selection; if mark is false the selection is cleared.

See also cursorForward().

void QLineEdit::cursorForward ( bool mark, int steps = 1 )

Moves the cursor forward steps characters. If mark is true each character moved over is added to the selection; if mark is false the selection is cleared.

See also cursorBackward().

int QLineEdit::cursorPositionAt ( const QPoint & pos )

Returns the cursor position under the point pos.

void QLineEdit::cursorPositionChanged ( int old, int new )   [signal]

This signal is emitted whenever the cursor moves. The previous position is given by old, and the new position by new.

See also setCursorPosition() and cursorPosition().

void QLineEdit::cursorWordBackward ( bool mark )

Moves the cursor one word backward. If mark is true, the word is also selected.

See also cursorWordForward().

void QLineEdit::cursorWordForward ( bool mark )

Moves the cursor one word forward. If mark is true, the word is also selected.

See also cursorWordBackward().

void QLineEdit::cut ()   [slot]

Copies the selected text to the clipboard and deletes it, if there is any, and if echoMode() is Normal.

If the current validator disallows deleting the selected text, cut() will copy without deleting.

See also copy(), paste(), and setValidator().

void QLineEdit::del ()

If no text is selected, deletes the character to the right of the text cursor. If any text is selected, the cursor is moved to the beginning of the selected text and the selected text is deleted.

See also backspace().

void QLineEdit::deselect ()

Deselects any selected text.

See also setSelection() and selectAll().

void QLineEdit::editingFinished ()   [signal]

This signal is emitted when the Return or Enter key is pressed or the line edit looses focus. Note that if there is a validator() or inputMask() set on the line edit and enter/return is pressed, the editingFinished() signal will only be emitted if the input follows the inputMask() and the validator() returns QValidator::Acceptable.

void QLineEdit::end ( bool mark )

Moves the text cursor to the end of the line unless it is already there. If mark is true, text is selected towards the last position; otherwise, any selected text is unselected if the cursor is moved.

See also home().

void QLineEdit::home ( bool mark )

Moves the text cursor to the beginning of the line unless it is already there. If mark is true, text is selected towards the first position; otherwise, any selected text is unselected if the cursor is moved.

See also end().

void QLineEdit::insert ( const QString & newText )

Deletes any selected text, inserts newText, and validates the result. If it is valid, it sets it as the new contents of the line edit.

See also setText() and clear().

void QLineEdit::keyPressEvent ( QKeyEvent * event )   [virtual protected]

Converts the given key press event into a line edit action.

If Return or Enter is pressed and the current text is valid (or can be made valid by the validator), the signal returnPressed() is emitted.

The default key bindings are listed in the class's detailed description.

Reimplemented from QWidget.

QSize QLineEdit::minimumSizeHint () const   [virtual]

Returns a minimum size for the line edit.

The width returned is enough for at least one character.

Reimplemented from QWidget.

void QLineEdit::paste ()   [slot]

Inserts the clipboard's text at the cursor position, deleting any selected text, providing the line edit is not read-only.

If the end result would not be acceptable to the current validator, nothing happens.

See also copy() and cut().

void QLineEdit::redo ()   [slot]

Redoes the last operation if redo is available.

void QLineEdit::returnPressed ()   [signal]

This signal is emitted when the Return or Enter key is pressed. Note that if there is a validator() or inputMask() set on the line edit, the returnPressed() signal will only be emitted if the input follows the inputMask() and the validator() returns QValidator::Acceptable.

void QLineEdit::selectAll ()   [slot]

Selects all the text (i.e. highlights it) and moves the cursor to the end. This is useful when a default value has been inserted because if the user types before clicking on the widget, the selected text will be deleted.

See also setSelection() and deselect().

void QLineEdit::selectionChanged ()   [signal]

This signal is emitted whenever the selection changes.

See also hasSelectedText() and selectedText().

int QLineEdit::selectionStart () const

selectionStart() returns the index of the first selected character in the line edit or -1 if no text is selected.

See also selectedText().

void QLineEdit::setSelection ( int start, int length )

Selects text from position start and for length characters. Negative lengths are allowed.

See also deselect(), selectAll(), and selectedText().

void QLineEdit::setValidator ( const QValidator * v )

Sets this line edit to only accept input that the validator, v, will accept. This allows you to place any arbitrary constraints on the text which may be entered.

If v == 0, setValidator() removes the current input validator. The initial setting is to have no input validator (i.e. any input is accepted up to maxLength()).

See also validator(), QIntValidator, QDoubleValidator, and QRegExpValidator.

QSize QLineEdit::sizeHint () const   [virtual]

Returns a recommended size for the widget.

The width returned, in pixels, is usually enough for about 15 to 20 characters.

Reimplemented from QWidget.

void QLineEdit::textChanged ( const QString & text )   [signal]

This signal is emitted whenever the text changes. The text argument is the new text.

Unlike textEdited(), this signal is also emitted when programmatically setting the text via setText().

void QLineEdit::textEdited ( const QString & text )   [signal]

This signal is emitted whenever the text is edited. The text argument is the next text.

Unlike textChanged(), this signal is not emitted when programmatically setting the text via setText().

void QLineEdit::undo ()   [slot]

Undoes the last operation if undo is available. Deselects any current selection, and updates the selection start to the current cursor position.

const QValidator * QLineEdit::validator () const

Returns a pointer to the current input validator, or 0 if no validator has been set.

See also setValidator().