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java.lang.Objectcom.trolltech.qt.QSignalEmitter
com.trolltech.qt.QtJambiObject
com.trolltech.qt.core.QObject
com.trolltech.qt.gui.QWidget
com.trolltech.qt.gui.QAbstractButton
com.trolltech.qt.gui.QPushButton
public class QPushButton
The QPushButton widget provides a command button.
The push button, or command button, is perhaps the most commonly used widget in any graphical user interface. Push (click) a button to command the computer to perform some action, or to answer a question. Typical buttons are OK, Apply, Cancel, Close, Yes, No and Help.
A command button is rectangular and typically displays a text label describing its action. A shortcut key can be specified by preceding the preferred character with an ampersand in the text. For example:
QPushButton *button = new QPushButton("&Download", this);
In this example the shortcut is Alt+D. See the QShortcut documentation for details (to display an actual ampersand, use '&&').
Push buttons display a textual label, and optionally a small icon. These can be set using the constructors and changed later using setText and setIcon. If the button is disabled the appearance of the text and icon will be manipulated with respect to the GUI style to make the button look "disabled".
A push button emits the signal clicked when it is activated by the mouse, the Spacebar or by a keyboard shortcut. Connect to this signal to perform the button's action. Push buttons also provide less commonly used signals, for example, pressed and released.
Command buttons in dialogs are by default auto-default buttons, i.e. they become the default push button automatically when they receive the keyboard input focus. A default button is a push button that is activated when the user presses the Enter or Return key in a dialog. You can change this with setAutoDefault. Note that auto-default buttons reserve a little extra space which is necessary to draw a default-button indicator. If you do not want this space around your buttons, call setAutoDefault(false).
Being so central, the button widget has grown to accommodate a great many variations in the past decade. The Microsoft style guide now shows about ten different states of Windows push buttons and the text implies that there are dozens more when all the combinations of features are taken into consideration.
The most important modes or states are:
As a general rule, use a push button when the application or dialog window performs an action when the user clicks on it (such as Apply, Cancel, Close and Help) and when the widget is supposed to have a wide, rectangular shape with a text label. Small, typically square buttons that change the state of the window rather than performing an action (such as the buttons in the top-right corner of the QFileDialog) are not command buttons, but tool buttons. Qt provides a special class (QToolButton) for these buttons.
If you need toggle behavior (see setCheckable) or a button that auto-repeats the activation signal when being pushed down like the arrows in a scroll bar (see setAutoRepeat), a command button is probably not what you want. When in doubt, use a tool button.
A variation of a command button is a menu button. These provide not just one command, but several, since when they are clicked they pop up a menu of options. Use the method setMenu to associate a popup menu with a push button.
Other classes of buttons are option buttons (see QRadioButton) and check boxes (see QCheckBox).
![]() | A push button shown in the Macintosh widget style. Note that when a button's width becomes smaller than 50 or its height becomes smaller than 30, the button's corners are changed from round to square. Use the setMinimumSize function to prevent this behavior. |
![]() | A push button shown in the Windows XP widget style. |
![]() | A push button shown in the Plastique widget style. |
In Qt, the QAbstractButton base class provides most of the modes and other API, and QPushButton provides GUI logic. See QAbstractButton for more information about the API.
Nested Class Summary |
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Nested classes/interfaces inherited from class com.trolltech.qt.gui.QWidget |
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QWidget.RenderFlag, QWidget.RenderFlags |
Nested classes/interfaces inherited from class com.trolltech.qt.QSignalEmitter |
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QSignalEmitter.Signal0, QSignalEmitter.Signal1<A>, QSignalEmitter.Signal2<A,B>, QSignalEmitter.Signal3<A,B,C>, QSignalEmitter.Signal4<A,B,C,D>, QSignalEmitter.Signal5<A,B,C,D,E>, QSignalEmitter.Signal6<A,B,C,D,E,F>, QSignalEmitter.Signal7<A,B,C,D,E,F,G>, QSignalEmitter.Signal8<A,B,C,D,E,F,G,H>, QSignalEmitter.Signal9<A,B,C,D,E,F,G,H,I> |
Field Summary |
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Fields inherited from class com.trolltech.qt.gui.QAbstractButton |
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clicked, pressed, released, toggled |
Fields inherited from class com.trolltech.qt.gui.QWidget |
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customContextMenuRequested |
Constructor Summary | |
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QPushButton()
Equivalent to QPushButton(0). |
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QPushButton(QIcon icon,
java.lang.String text)
Equivalent to QPushButton(icon, text, 0). |
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QPushButton(QIcon icon,
java.lang.String text,
QWidget parent)
Constructs a push button with an icon and a text, and a parent. |
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QPushButton(QWidget parent)
Constructs a push button with no text and a parent. |
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QPushButton(java.lang.String text)
Equivalent to QPushButton(text, 0). |
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QPushButton(java.lang.String text,
QWidget parent)
Constructs a push button with the parent parent and the text text. |
Method Summary | |
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boolean |
autoDefault()
Returns whether the push button is an auto default button. |
boolean |
event(QEvent e)
This is the main event handler; it handles event arg__1. You can reimplement this function in a subclass, but we recommend using one of the specialized event handlers instead. Key press and release events are treated differently from other events. event checks for Tab and Shift+Tab and tries to move the focus appropriately. If there is no widget to move the focus to (or the key press is not Tab or Shift+Tab), event calls keyPressEvent. Mouse and tablet event handling is also slightly special: only when the widget is enabled, event will call the specialized handlers such as mousePressEvent; otherwise it will discard the event. This function returns true if the event was recognized, otherwise it returns false. If the recognized event was accepted (see QEvent::accepted), any further processing such as event propagation to the parent widget stops. |
protected void |
focusInEvent(QFocusEvent arg__1)
This event handler can be reimplemented in a subclass to receive keyboard focus events (focus received) for the widget. The event is passed in the arg__1 parameter A widget normally must setFocusPolicy to something other than Qt::NoFocus in order to receive focus events. (Note that the application programmer can call setFocus on any widget, even those that do not normally accept focus.) The default implementation updates the widget (except for windows that do not specify a focusPolicy). |
protected void |
focusOutEvent(QFocusEvent arg__1)
This event handler can be reimplemented in a subclass to receive keyboard focus events (focus lost) for the widget. The events is passed in the arg__1 parameter. A widget normally must setFocusPolicy to something other than Qt::NoFocus in order to receive focus events. (Note that the application programmer can call setFocus on any widget, even those that do not normally accept focus.) The default implementation updates the widget (except for windows that do not specify a focusPolicy). |
static QPushButton |
fromNativePointer(QNativePointer nativePointer)
This function returns the QPushButton instance pointed to by nativePointer |
protected void |
initStyleOption(QStyleOptionButton option)
Initialize option with the values from this QPushButton. |
boolean |
isDefault()
Returns whether the push button is the default button. |
boolean |
isFlat()
Returns whether the button border is raised. |
protected void |
keyPressEvent(QKeyEvent arg__1)
This event handler, for event arg__1, can be reimplemented in a subclass to receive key press events for the widget. A widget must call setFocusPolicy to accept focus initially and have focus in order to receive a key press event. If you reimplement this handler, it is very important that you ignore() the event if you do not understand it, so that the widget's parent can interpret it. The default implementation closes popup widgets if the user presses Esc. Otherwise the event is ignored. |
QMenu |
menu()
Returns the button's associated popup menu or 0 if no popup menu has been set. |
QSize |
minimumSizeHint()
Returns the recommended minimum size for the widget. |
protected void |
paintEvent(QPaintEvent arg__1)
This event handler can be reimplemented in a subclass to receive paint events which are passed in the arg__1 parameter. A paint event is a request to repaint all or part of the widget. It can happen as a result of repaint or update, or because the widget was obscured and has now been uncovered, or for many other reasons. Many widgets can simply repaint their entire surface when asked to, but some slow widgets need to optimize by painting only the requested region: QPaintEvent::region(). This speed optimization does not change the result, as painting is clipped to that region during event processing. QListView and QTableView do this, for example. Qt also tries to speed up painting by merging multiple paint events into one. When update is called several times or the window system sends several paint events, Qt merges these events into one event with a larger region (see QRegion::united()). repaint does not permit this optimization, so we suggest using update whenever possible. When the paint event occurs, the update region has normally been erased, so that you're painting on the widget's background. The background can be set using setBackgroundRole and setPalette. From Qt 4.0, QWidget automatically double-buffers its painting, so there's no need to write double-buffering code in paintEvent to avoid flicker. Note: Under X11 it is possible to toggle the global double buffering by calling qt_x11_set_global_double_buffer(). Example usage: ... extern void qt_x11_set_global_double_buffer(bool); qt_x11_set_global_double_buffer(false); ... Note: In general, one should refrain from calling update or repaint inside of paintEvent. For example, calling update or repaint on children inside a paintEvent results in undefined behavior; the child may or may not get a paint event. |
void |
setAutoDefault(boolean arg__1)
Sets whether the push button is an auto default button to arg__1. |
void |
setDefault(boolean arg__1)
Sets whether the push button is the default button to arg__1. |
void |
setFlat(boolean arg__1)
Sets whether the button border is raised to arg__1. |
void |
setMenu(QMenu menu)
Associates the popup menu menu with this push button. |
void |
showMenu()
Shows (pops up) the associated popup menu. |
QSize |
sizeHint()
Returns the recommended size for the widget. |
Methods inherited from class com.trolltech.qt.gui.QAbstractButton |
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animateClick, animateClick, autoExclusive, autoRepeat, autoRepeatDelay, autoRepeatInterval, changeEvent, checkStateSet, click, group, hitButton, icon, iconSize, isCheckable, isChecked, isDown, keyReleaseEvent, mouseMoveEvent, mousePressEvent, mouseReleaseEvent, nextCheckState, setAutoExclusive, setAutoRepeat, setAutoRepeatDelay, setAutoRepeatInterval, setCheckable, setChecked, setDown, setIcon, setIconSize, setShortcut, setShortcut, setShortcut, setText, shortcut, text, timerEvent, toggle |
Methods inherited from class com.trolltech.qt.core.QObject |
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blockSignals, childEvent, children, connectSlotsByName, customEvent, disposeLater, dumpObjectInfo, dumpObjectTree, dynamicPropertyNames, eventFilter, findChild, findChild, findChild, findChildren, findChildren, findChildren, findChildren, installEventFilter, isWidgetType, killTimer, moveToThread, objectName, parent, property, removeEventFilter, setObjectName, setParent, setProperty, signalsBlocked, startTimer, thread |
Methods inherited from class com.trolltech.qt.QtJambiObject |
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dispose, disposed, finalize, reassignNativeResources, tr, tr, tr |
Methods inherited from class com.trolltech.qt.QSignalEmitter |
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disconnect, disconnect, signalSender |
Methods inherited from class java.lang.Object |
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clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Methods inherited from interface com.trolltech.qt.QtJambiInterface |
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disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
Constructor Detail |
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public QPushButton(java.lang.String text)
Equivalent to QPushButton(text, 0).
public QPushButton(java.lang.String text, QWidget parent)
Constructs a push button with the parent parent and the text text.
public QPushButton(QIcon icon, java.lang.String text)
Equivalent to QPushButton(icon, text, 0).
public QPushButton(QIcon icon, java.lang.String text, QWidget parent)
Constructs a push button with an icon and a text, and a parent.
Note that you can also pass a QPixmap object as an icon (thanks to the implicit type conversion provided by C++).
public QPushButton()
Equivalent to QPushButton(0).
public QPushButton(QWidget parent)
Constructs a push button with no text and a parent.
Method Detail |
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public final boolean autoDefault()
Returns whether the push button is an auto default button.
If this property is set to true then the push button is an auto default button.
In some GUI styles a default button is drawn with an extra frame around it, up to 3 pixels or more. Qt automatically keeps this space free around auto-default buttons, i.e. auto-default buttons may have a slightly larger size hint.
This property's default is true for buttons that have a QDialog parent; otherwise it defaults to false.
See the default property for details of how default and auto-default interact.
public final boolean isDefault()
Returns whether the push button is the default button.
Default and autodefault buttons decide what happens when the user presses enter in a dialog.
A button with this property set to true (i.e., the dialog's default button,) will automatically be pressed when the user presses enter, with one exception: if an autoDefault button currently has focus, the autoDefault button is pressed. When the dialog has autoDefault buttons but no default button, pressing enter will press either the autoDefault button that currently has focus, or if no button has focus, the next autoDefault button in the focus chain.
In a dialog, only one push button at a time can be the default button. This button is then displayed with an additional frame (depending on the GUI style).
The default button behavior is provided only in dialogs. Buttons can always be clicked from the keyboard by pressing Spacebar when the button has focus.
If the default property is set to false on the current default button while the dialog is visible, a new default will automatically be assigned the next time a pushbutton in the dialog receives focus.
This property's default is false.
public final boolean isFlat()
Returns whether the button border is raised.
This property's default is false. If this property is set, most styles will not paint the button background unless the button is being pressed. setAutoFillBackground can be used to ensure that the background is filled using the QPalette::Button brush.
public final QMenu menu()
Returns the button's associated popup menu or 0 if no popup menu has been set.
public final void setAutoDefault(boolean arg__1)
Sets whether the push button is an auto default button to arg__1.
If this property is set to true then the push button is an auto default button.
In some GUI styles a default button is drawn with an extra frame around it, up to 3 pixels or more. Qt automatically keeps this space free around auto-default buttons, i.e. auto-default buttons may have a slightly larger size hint.
This property's default is true for buttons that have a QDialog parent; otherwise it defaults to false.
See the default property for details of how default and auto-default interact.
public final void setDefault(boolean arg__1)
Sets whether the push button is the default button to arg__1.
Default and autodefault buttons decide what happens when the user presses enter in a dialog.
A button with this property set to true (i.e., the dialog's default button,) will automatically be pressed when the user presses enter, with one exception: if an autoDefault button currently has focus, the autoDefault button is pressed. When the dialog has autoDefault buttons but no default button, pressing enter will press either the autoDefault button that currently has focus, or if no button has focus, the next autoDefault button in the focus chain.
In a dialog, only one push button at a time can be the default button. This button is then displayed with an additional frame (depending on the GUI style).
The default button behavior is provided only in dialogs. Buttons can always be clicked from the keyboard by pressing Spacebar when the button has focus.
If the default property is set to false on the current default button while the dialog is visible, a new default will automatically be assigned the next time a pushbutton in the dialog receives focus.
This property's default is false.
public final void setFlat(boolean arg__1)
Sets whether the button border is raised to arg__1.
This property's default is false. If this property is set, most styles will not paint the button background unless the button is being pressed. setAutoFillBackground can be used to ensure that the background is filled using the QPalette::Button brush.
public final void setMenu(QMenu menu)
Associates the popup menu menu with this push button. This turns the button into a menu button, which in some styles will produce a small triangle to the right of the button's text.
Ownership of the menu is not transferred to the push button.
![]() | ![]() | Push buttons with popup menus shown in the Plastique widget style (left) and Cleanlooks widget style (right). |
public final void showMenu()
Shows (pops up) the associated popup menu. If there is no such menu, this function does nothing. This function does not return until the popup menu has been closed by the user.
public boolean event(QEvent e)
This is the main event handler; it handles event arg__1. You can reimplement this function in a subclass, but we recommend using one of the specialized event handlers instead.
Key press and release events are treated differently from other events. event checks for Tab and Shift+Tab and tries to move the focus appropriately. If there is no widget to move the focus to (or the key press is not Tab or Shift+Tab), event calls keyPressEvent.
Mouse and tablet event handling is also slightly special: only when the widget is enabled, event will call the specialized handlers such as mousePressEvent; otherwise it will discard the event.
This function returns true if the event was recognized, otherwise it returns false. If the recognized event was accepted (see QEvent::accepted), any further processing such as event propagation to the parent widget stops.
event
in class QAbstractButton
protected void focusInEvent(QFocusEvent arg__1)
This event handler can be reimplemented in a subclass to receive keyboard focus events (focus received) for the widget. The event is passed in the arg__1 parameter
A widget normally must setFocusPolicy to something other than Qt::NoFocus in order to receive focus events. (Note that the application programmer can call setFocus on any widget, even those that do not normally accept focus.)
The default implementation updates the widget (except for windows that do not specify a focusPolicy).
focusInEvent
in class QAbstractButton
protected void focusOutEvent(QFocusEvent arg__1)
This event handler can be reimplemented in a subclass to receive keyboard focus events (focus lost) for the widget. The events is passed in the arg__1 parameter.
A widget normally must setFocusPolicy to something other than Qt::NoFocus in order to receive focus events. (Note that the application programmer can call setFocus on any widget, even those that do not normally accept focus.)
The default implementation updates the widget (except for windows that do not specify a focusPolicy).
focusOutEvent
in class QAbstractButton
protected void keyPressEvent(QKeyEvent arg__1)
This event handler, for event arg__1, can be reimplemented in a subclass to receive key press events for the widget.
A widget must call setFocusPolicy to accept focus initially and have focus in order to receive a key press event.
If you reimplement this handler, it is very important that you ignore() the event if you do not understand it, so that the widget's parent can interpret it.
The default implementation closes popup widgets if the user presses Esc. Otherwise the event is ignored.
keyPressEvent
in class QAbstractButton
public QSize minimumSizeHint()
Returns the recommended minimum size for the widget.
If the value of this property is an invalid size, no minimum size is recommended.
The default implementation of minimumSizeHint returns an invalid size if there is no layout for this widget, and returns the layout's minimum size otherwise. Most built-in widgets reimplement minimumSizeHint.
QLayout will never resize a widget to a size smaller than the minimum size hint unless minimumSize is set or the size policy is set to QSizePolicy::Ignore. If minimumSize is set, the minimum size hint will be ignored.
minimumSizeHint
in class QWidget
protected void paintEvent(QPaintEvent arg__1)
This event handler can be reimplemented in a subclass to receive paint events which are passed in the arg__1 parameter.
A paint event is a request to repaint all or part of the widget. It can happen as a result of repaint or update, or because the widget was obscured and has now been uncovered, or for many other reasons.
Many widgets can simply repaint their entire surface when asked to, but some slow widgets need to optimize by painting only the requested region: QPaintEvent::region(). This speed optimization does not change the result, as painting is clipped to that region during event processing. QListView and QTableView do this, for example.
Qt also tries to speed up painting by merging multiple paint events into one. When update is called several times or the window system sends several paint events, Qt merges these events into one event with a larger region (see QRegion::united()). repaint does not permit this optimization, so we suggest using update whenever possible.
When the paint event occurs, the update region has normally been erased, so that you're painting on the widget's background.
The background can be set using setBackgroundRole and setPalette.
From Qt 4.0, QWidget automatically double-buffers its painting, so there's no need to write double-buffering code in paintEvent to avoid flicker.
Note: Under X11 it is possible to toggle the global double buffering by calling qt_x11_set_global_double_buffer(). Example usage:
... extern void qt_x11_set_global_double_buffer(bool); qt_x11_set_global_double_buffer(false); ...
Note: In general, one should refrain from calling update or repaint inside of paintEvent. For example, calling update or repaint on children inside a paintEvent results in undefined behavior; the child may or may not get a paint event.
paintEvent
in class QAbstractButton
public QSize sizeHint()
Returns the recommended size for the widget.
If the value of this property is an invalid size, no size is recommended.
The default implementation of sizeHint returns an invalid size if there is no layout for this widget, and returns the layout's preferred size otherwise.
sizeHint
in class QWidget
public static QPushButton fromNativePointer(QNativePointer nativePointer)
nativePointer
- the QNativePointer of which object should be returned.protected final void initStyleOption(QStyleOptionButton option)
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