QAbstractAnimation Class

The QAbstractAnimation class is the base of all animations. More...

Header: #include <QAbstractAnimation>
CMake: find_package(Qt6 COMPONENTS Core REQUIRED)
target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake: QT += core
Inherits: QObject
Inherited By:

QAnimationGroup, QPauseAnimation, and QVariantAnimation

Public Types

enum DeletionPolicy { KeepWhenStopped, DeleteWhenStopped }
enum Direction { Forward, Backward }
enum State { Stopped, Paused, Running }


Public Functions

QAbstractAnimation(QObject *parent = nullptr)
virtual ~QAbstractAnimation()
int currentLoop() const
int currentLoopTime() const
int currentTime() const
QAbstractAnimation::Direction direction() const
virtual int duration() const = 0
QAnimationGroup *group() const
int loopCount() const
void setDirection(QAbstractAnimation::Direction direction)
void setLoopCount(int loopCount)
QAbstractAnimation::State state() const
int totalDuration() const

Public Slots

void pause()
void resume()
void setCurrentTime(int msecs)
void setPaused(bool paused)
void start(QAbstractAnimation::DeletionPolicy policy = KeepWhenStopped)
void stop()


void currentLoopChanged(int currentLoop)
void directionChanged(QAbstractAnimation::Direction newDirection)
void finished()
void stateChanged(QAbstractAnimation::State newState, QAbstractAnimation::State oldState)

Protected Functions

virtual void updateCurrentTime(int currentTime) = 0
virtual void updateDirection(QAbstractAnimation::Direction direction)
virtual void updateState(QAbstractAnimation::State newState, QAbstractAnimation::State oldState)

Reimplemented Protected Functions

virtual bool event(QEvent *event) override

Detailed Description

The class defines the functions for the functionality shared by all animations. By inheriting this class, you can create custom animations that plug into the rest of the animation framework.

The progress of an animation is given by its current time (currentLoopTime()), which is measured in milliseconds from the start of the animation (0) to its end (duration()). The value is updated automatically while the animation is running. It can also be set directly with setCurrentTime().

At any point an animation is in one of three states: Running, Stopped, or Paused--as defined by the State enum. The current state can be changed by calling start(), stop(), pause(), or resume(). An animation will always reset its current time when it is started. If paused, it will continue with the same current time when resumed. When an animation is stopped, it cannot be resumed, but will keep its current time (until started again). QAbstractAnimation will emit stateChanged() whenever its state changes.

An animation can loop any number of times by setting the loopCount property. When an animation's current time reaches its duration(), it will reset the current time and keep running. A loop count of 1 (the default value) means that the animation will run one time. Note that a duration of -1 means that the animation will run until stopped; the current time will increase indefinitely. When the current time equals duration() and the animation is in its final loop, the Stopped state is entered, and the finished() signal is emitted.

QAbstractAnimation provides pure virtual functions used by subclasses to track the progress of the animation: duration() and updateCurrentTime(). The duration() function lets you report a duration for the animation (as discussed above). The animation framework calls updateCurrentTime() when current time has changed. By reimplementing this function, you can track the animation progress. Note that neither the interval between calls nor the number of calls to this function are defined; though, it will normally be 60 updates per second.

By reimplementing updateState(), you can track the animation's state changes, which is particularly useful for animations that are not driven by time.

See also QVariantAnimation, QPropertyAnimation, QAnimationGroup, and The Animation Framework.

Member Type Documentation

enum QAbstractAnimation::DeletionPolicy

QAbstractAnimation::KeepWhenStopped0The animation will not be deleted when stopped.
QAbstractAnimation::DeleteWhenStopped1The animation will be automatically deleted when stopped.

enum QAbstractAnimation::Direction

This enum describes the direction of the animation when in Running state.

QAbstractAnimation::Forward0The current time of the animation increases with time (i.e., moves from 0 and towards the end / duration).
QAbstractAnimation::Backward1The current time of the animation decreases with time (i.e., moves from the end / duration and towards 0).

See also direction.

enum QAbstractAnimation::State

This enum describes the state of the animation.

QAbstractAnimation::Stopped0The animation is not running. This is the initial state of QAbstractAnimation, and the state QAbstractAnimation reenters when finished. The current time remain unchanged until either setCurrentTime() is called, or the animation is started by calling start().
QAbstractAnimation::Paused1The animation is paused (i.e., temporarily suspended). Calling resume() will resume animation activity.
QAbstractAnimation::Running2The animation is running. While control is in the event loop, QAbstractAnimation will update its current time at regular intervals, calling updateCurrentTime() when appropriate.

See also state() and stateChanged().

Property Documentation

[bindable read-only] currentLoop : int

Note: This property supports QProperty bindings.

This property holds the current loop of the animation

This property describes the current loop of the animation. By default, the animation's loop count is 1, and so the current loop will always be 0. If the loop count is 2 and the animation runs past its duration, it will automatically rewind and restart at current time 0, and current loop 1, and so on.

When the current loop changes, QAbstractAnimation emits the currentLoopChanged() signal.

[bindable] currentTime : int

Note: This property supports QProperty bindings.

This property holds the current time and progress of the animation

This property describes the animation's current time. You can change the current time by calling setCurrentTime, or you can call start() and let the animation run, setting the current time automatically as the animation progresses.

The animation's current time starts at 0, and ends at totalDuration().

Note: You can bind other properties to currentTime, but it is not recommended setting bindings to it. As animation progresses, the currentTime is updated automatically, which cancels its bindings.

See also loopCount and currentLoopTime().

[bindable] direction : Direction

Note: This property supports QProperty bindings.

This property holds the direction of the animation when it is in Running state.

This direction indicates whether the time moves from 0 towards the animation duration, or from the value of the duration and towards 0 after start() has been called.

By default, this property is set to Forward.

[read-only] duration : const int

This property holds the duration of the animation.

If the duration is -1, it means that the duration is undefined. In this case, loopCount is ignored.

Access functions:

virtual int duration() const = 0

[bindable] loopCount : int

Note: This property supports QProperty bindings.

This property holds the loop count of the animation

This property describes the loop count of the animation as an integer. By default this value is 1, indicating that the animation should run once only, and then stop. By changing it you can let the animation loop several times. With a value of 0, the animation will not run at all, and with a value of -1, the animation will loop forever until stopped. It is not supported to have loop on an animation that has an undefined duration. It will only run once.

[bindable read-only] state : State

Note: This property supports QProperty bindings.

state of the animation.

This property describes the current state of the animation. When the animation state changes, QAbstractAnimation emits the stateChanged() signal.

Note: State updates might cause updates of the currentTime property, which, in turn, can cancel its bindings. So be careful when setting bindings to the currentTime property, when you expect the state of the animation to change.

Member Function Documentation

QAbstractAnimation::QAbstractAnimation(QObject *parent = nullptr)

Constructs the QAbstractAnimation base class, and passes parent to QObject's constructor.

See also QVariantAnimation and QAnimationGroup.

[signal] void QAbstractAnimation::currentLoopChanged(int currentLoop)

QAbstractAnimation emits this signal whenever the current loop changes. currentLoop is the current loop.

Note: Notifier signal for property currentLoop.

See also currentLoop() and loopCount().

[signal] void QAbstractAnimation::directionChanged(QAbstractAnimation::Direction newDirection)

QAbstractAnimation emits this signal whenever the direction has been changed. newDirection is the new direction.

Note: Notifier signal for property direction.

See also direction.

[signal] void QAbstractAnimation::finished()

QAbstractAnimation emits this signal after the animation has stopped and has reached the end.

This signal is emitted after stateChanged().

See also stateChanged().

[slot] void QAbstractAnimation::pause()

Pauses the animation. When the animation is paused, state() returns Paused. The value of currentTime will remain unchanged until resume() or start() is called. If you want to continue from the current time, call resume().

See also start(), state(), and resume().

[slot] void QAbstractAnimation::resume()

Resumes the animation after it was paused. When the animation is resumed, it emits the resumed() and stateChanged() signals. The currenttime is not changed.

See also start(), pause(), and state().

[slot] void QAbstractAnimation::setPaused(bool paused)

If paused is true, the animation is paused. If paused is false, the animation is resumed.

See also state(), pause(), and resume().

[slot] void QAbstractAnimation::start(QAbstractAnimation::DeletionPolicy policy = KeepWhenStopped)

Starts the animation. The policy argument says whether or not the animation should be deleted when it's done. When the animation starts, the stateChanged() signal is emitted, and state() returns Running. When control reaches the event loop, the animation will run by itself, periodically calling updateCurrentTime() as the animation progresses.

If the animation is currently stopped or has already reached the end, calling start() will rewind the animation and start again from the beginning. When the animation reaches the end, the animation will either stop, or if the loop level is more than 1, it will rewind and continue from the beginning.

If the animation is already running, this function does nothing.

See also stop() and state().

[signal] void QAbstractAnimation::stateChanged(QAbstractAnimation::State newState, QAbstractAnimation::State oldState)

QAbstractAnimation emits this signal whenever the state of the animation has changed from oldState to newState. This signal is emitted after the virtual updateState() function is called.

Note: Notifier signal for property state.

See also updateState().

[slot] void QAbstractAnimation::stop()

Stops the animation. When the animation is stopped, it emits the stateChanged() signal, and state() returns Stopped. The current time is not changed.

If the animation stops by itself after reaching the end (i.e., currentLoopTime() == duration() and currentLoop() > loopCount() - 1), the finished() signal is emitted.

See also start() and state().

[virtual] QAbstractAnimation::~QAbstractAnimation()

Stops the animation if it's running, then destroys the QAbstractAnimation. If the animation is part of a QAnimationGroup, it is automatically removed before it's destroyed.

int QAbstractAnimation::currentLoopTime() const

Returns the current time inside the current loop. It can go from 0 to duration().

See also duration() and currentTime.

[pure virtual] int QAbstractAnimation::duration() const

This pure virtual function returns the duration of the animation, and defines for how long QAbstractAnimation should update the current time. This duration is local, and does not include the loop count.

A return value of -1 indicates that the animation has no defined duration; the animation should run forever until stopped. This is useful for animations that are not time driven, or where you cannot easily predict its duration (e.g., event driven audio playback in a game).

If the animation is a parallel QAnimationGroup, the duration will be the longest duration of all its animations. If the animation is a sequential QAnimationGroup, the duration will be the sum of the duration of all its animations.

Note: Getter function for property duration.

See also loopCount.

[override virtual protected] bool QAbstractAnimation::event(QEvent *event)

Reimplements: QObject::event(QEvent *e).

QAnimationGroup *QAbstractAnimation::group() const

If this animation is part of a QAnimationGroup, this function returns a pointer to the group; otherwise, it returns nullptr.

See also QAnimationGroup::addAnimation().

int QAbstractAnimation::totalDuration() const

Returns the total and effective duration of the animation, including the loop count.

See also duration() and currentTime.

[pure virtual protected] void QAbstractAnimation::updateCurrentTime(int currentTime)

This pure virtual function is called every time the animation's currentTime changes.

See also updateState().

[virtual protected] void QAbstractAnimation::updateDirection(QAbstractAnimation::Direction direction)

This virtual function is called by QAbstractAnimation when the direction of the animation is changed. The direction argument is the new direction.

See also setDirection() and direction().

[virtual protected] void QAbstractAnimation::updateState(QAbstractAnimation::State newState, QAbstractAnimation::State oldState)

This virtual function is called by QAbstractAnimation when the state of the animation is changed from oldState to newState.

See also start(), stop(), pause(), and resume().

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