diff options
Diffstat (limited to 'doc/src/frameworks-technologies/animation.qdoc')
| -rw-r--r-- | doc/src/frameworks-technologies/animation.qdoc | 377 |
1 files changed, 377 insertions, 0 deletions
diff --git a/doc/src/frameworks-technologies/animation.qdoc b/doc/src/frameworks-technologies/animation.qdoc new file mode 100644 index 0000000..d495aeb --- /dev/null +++ b/doc/src/frameworks-technologies/animation.qdoc @@ -0,0 +1,377 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain +** additional rights. These rights are described in the Nokia Qt LGPL +** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this +** package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at http://qt.nokia.com/contact. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! + \group animation + \title Animation Framework +*/ + +/*! + \page animation-overview.html + \title The Animation Framework + + \brief An overview of the Animation Framework + + \ingroup frameworks-technologies + + \keyword Animation + + The animation framework is part of the Kinetic project, and aims + to provide an easy way for creating animated and smooth GUI's. By + animating Qt properties, the framework provides great freedom for + animating widgets and other \l{QObject}s. The framework can also + be used with the Graphics View framework. + + In this overview, we explain the basics of its architecture. We + also show examples of the most common techniques that the + framework allows for animating QObjects and graphics items. + + \tableofcontents + + \section1 The Animation Architecture + + We will in this section take a high-level look at the animation + framework's architecture and how it is used to animate Qt + properties. The following diagram shows the most important classes + in the animation framework. + + \image animations-architecture.png + + The animation framework foundation consists of the base class + QAbstractAnimation, and its two subclasses QVariantAnimation and + QAnimationGroup. QAbstractAnimation is the ancestor of all + animations. It represents basic properties that are common for all + animations in the framework; notably, the ability to start, stop, + and pause an animation. It is also receives the time change + notifications. + + The animation framework further provides the QPropertyAnimation + class, which inherits QVariantAnimation and performs animation of + a Qt property, which is part of Qt's \l{Meta-Object + System}{meta-object system}. The class performs an interpolation + over the property using an easing curve. So when you want to + animate a value, you can declare it as a property and make your + class a QObject. Note that this gives us great freedom in + animating already existing widgets and other \l{QObject}s. + + Complex animations can be constructed by building a tree structure + of \l{QAbstractAnimation}s. The tree is built by using + \l{QAnimationGroup}s, which function as containers for other + animations. Note also that the groups are subclasses of + QAbstractAnimation, so groups can themselves contain other groups. + + The animation framework can be used on its own, but is also + designed to be part of the state machine framework (See the + \l{The State Machine Framework}{state machine framework} for an + introduction to the Qt state machine). The state machine provides + a special state that can play an animation. A QState can also set + properties when the state is entered or exited, and this special + animation state will interpolate between these values when given a + QPropertyAnimation. We will look more closely at this later. + + Behind the scenes, the animations are controlled by a global + timer, which sends \l{QAbstractAnimation::updateCurrentTime()}{updates} to + all animations that are playing. + + For detailed descriptions of the classes' function and roles in + the framework, please look up their class descriptions. + + \section1 Classes in the Animation Framework + + These classes provide a framework for creating both simple and complex + animations. + + \annotatedlist animation + + \section1 Animating Qt Properties + + As mentioned in the previous section, the QPropertyAnimation class + can interpolate over Qt properties. It is this class that should + be used for animation of values; in fact, its superclass, + QVariantAnimation, is an abstract class, and cannot be used + directly. + + A major reason we chose to animate Qt properties is that it + presents us with freedom to animate already existing classes in + the Qt API. Notably, the QWidget class (which we can also embed in + a QGraphicsView) has properties for its bounds, colors, etc. + Let's look at a small example: + + \code + QPushButton button("Animated Button"); + button.show(); + + QPropertyAnimation animation(&button, "geometry"); + animation.setDuration(10000); + animation.setStartValue(QRect(0, 0, 100, 30)); + animation.setEndValue(QRect(250, 250, 100, 30)); + + animation.start(); + \endcode + + This code will move \c button from the top left corner of the + screen to the position (250, 250) in 10 seconds (10000 milliseconds). + + The example above will do a linear interpolation between the + start and end value. It is also possible to set values + situated between the start and end value. The interpolation + will then go by these points. + + \code + QPushButton button("Animated Button"); + button.show(); + + QPropertyAnimation animation(&button, "geometry"); + animation.setDuration(10000); + + animation.setKeyValueAt(0, QRect(0, 0, 100, 30)); + animation.setKeyValueAt(0.8, QRect(250, 250, 100, 30)); + animation.setKeyValueAt(1, QRect(0, 0, 100, 30)); + + animation.start(); + \endcode + + In this example, the animation will take the button to (250, 250) + in 8 seconds, and then move it back to its original position in + the remaining 2 seconds. The movement will be linearly + interpolated between these points. + + You also have the possibility to animate values of a QObject + that is not declared as a Qt property. The only requirement is + that this value has a setter. You can then subclass the class + containing the value and declare a property that uses this setter. + Note that each Qt property requires a getter, so you will need to + provide a getter yourself if this is not defined. + + \code + class MyGraphicsRectItem : public QObject, public QGraphicsRectItem + { + Q_OBJECT + Q_PROPERTY(QRectF geometry READ geometry WRITE setGeometry) + }; + \endcode + + In the above code example, we subclass QGraphicsRectItem and + define a geometry property. We can now animate the widgets + geometry even if QGraphicsRectItem does not provide the geometry + property. + + For a general introduction to the Qt property system, see its + \l{Qt's Property System}{overview}. + + \section1 Animations and the Graphics View Framework + + When you want to animate \l{QGraphicsItem}s, you also use + QPropertyAnimation. However, QGraphicsItem does not inherit QObject. + A good solution is to subclass the graphics item you wish to animate. + This class will then also inherit QObject. + This way, QPropertyAnimation can be used for \l{QGraphicsItem}s. + The example below shows how this is done. Another possibility is + to inherit QGraphicsWidget, which already is a QObject. + + \code + class Pixmap : public QObject, public QGraphicsPixmapItem + { + Q_OBJECT + Q_PROPERTY(QPointF pos READ pos WRITE setPos) + ... + \endcode + + As described in the previous section, we need to define + properties that we wish to animate. + + Note that QObject must be the first class inherited as the + meta-object system demands this. + + \section1 Easing Curves + + As mentioned, QPropertyAnimation performs an interpolation between + the start and end property value. In addition to adding more key + values to the animation, you can also use an easing curve. Easing + curves describe a function that controls how the speed of the + interpolation between 0 and 1 should be, and are useful if you + want to control the speed of an animation without changing the + path of the interpolation. + + \code + QPushButton button("Animated Button"); + button.show(); + + QPropertyAnimation animation(&button, "geometry"); + animation.setDuration(3000); + animation.setStartValue(QRect(0, 0, 100, 30)); + animation.setEndValue(QRect(250, 250, 100, 30)); + + animation.setEasingCurve(QEasingCurve::OutBounce); + + animation.start(); + \endcode + + Here the animation will follow a curve that makes it bounce like a + ball as if it was dropped from the start to the end position. + QEasingCurve has a large collection of curves for you to choose + from. These are defined by the QEasingCurve::Type enum. If you are + in need of another curve, you can also implement one yourself, and + register it with QEasingCurve. + + \omit Drop this for the first Lab release + (Example of custom easing curve (without the actual impl of + the function I expect) + \endomit + + \section1 Putting Animations Together + + An application will often contain more than one animation. For + instance, you might want to move more than one graphics item + simultaneously or move them in sequence after each other. + + The subclasses of QAnimationGroup (QSequentialAnimationGroup and + QParallelAnimationGroup) are containers for other animations so + that these animations can be animated either in sequence or + parallel. The QAnimationGroup is an example of an animation that + does not animate properties, but it gets notified of time changes + periodically. This enables it to forward those time changes to its + contained animations, and thereby controlling when its animations + are played. + + Let's look at code examples that use both + QSequentialAnimationGroup and QParallelAnimationGroup, starting + off with the latter. + + \code + QPushButton *bonnie = new QPushButton("Bonnie"); + bonnie->show(); + + QPushButton *clyde = new QPushButton("Clyde"); + clyde->show(); + + QPropertyAnimation *anim1 = new QPropertyAnimation(bonnie, "geometry"); + // Set up anim1 + + QPropertyAnimation *anim2 = new QPropertyAnimation(clyde, "geometry"); + // Set up anim2 + + QParallelAnimationGroup *group = new QParallelAnimationGroup; + group->addAnimation(anim1); + group->addAnimation(anim2); + + group->start(); + \endcode + + A parallel group plays more than one animation at the same time. + Calling its \l{QAbstractAnimation::}{start()} function will start + all animations it governs. + + \code + QPushButton button("Animated Button"); + button.show(); + + QPropertyAnimation anim1(&button, "geometry"); + anim1.setDuration(3000); + anim1.setStartValue(QRect(0, 0, 100, 30)); + anim1.setEndValue(QRect(500, 500, 100, 30)); + + QPropertyAnimation anim2(&button, "geometry"); + anim2.setDuration(3000); + anim2.setStartValue(QRect(500, 500, 100, 30)); + anim2.setEndValue(QRect(1000, 500, 100, 30)); + + QSequentialAnimationGroup group; + + group.addAnimation(&anim1); + group.addAnimation(&anim2); + + group.start(); + \endcode + + As you no doubt have guessed, QSequentialAnimationGroup plays + its animations in sequence. It starts the next animation in + the list after the previous is finished. + + Since an animation group is an animation itself, you can add + it to another group. This way, you can build a tree structure + of animations which specifies when the animations are played + in relation to each other. + + \section1 Animations and States + + When using a \l{The State Machine Framework}{state machine}, we + can associate one or more animations to a transition between states + using a QSignalTransition or QEventTransition class. These classes + are both derived from QAbstractTransition, which defines the + convenience function \l{QAbstractTransition::}{addAnimation()} that + enables the appending of one or more animations triggered when the + transition occurs. + + We also have the possibility to associate properties with the + states rather than setting the start and end values ourselves. + Below is a complete code example that animates the geometry of a + QPushButton. + + \code + QPushButton *button = new QPushButton("Animated Button"); + button->show(); + + QStateMachine *machine = new QStateMachine; + + QState *state1 = new QState(machine->rootState()); + state1->assignProperty(button, "geometry", QRect(0, 0, 100, 30)); + machine->setInitialState(state1); + + QState *state2 = new QState(machine->rootState()); + state2->assignProperty(button, "geometry", QRect(250, 250, 100, 30)); + + QSignalTransition *transition1 = state1->addTransition(button, + SIGNAL(clicked()), state2); + transition1->addAnimation(new QPropertyAnimation(button, "geometry")); + + QSignalTransition *transition2 = state2->addTransition(button, + SIGNAL(clicked()), state1); + transition2->addAnimation(new QPropertyAnimation(button, "geometry")); + + machine->start(); + \endcode + + For a more comprehensive example of how to use the state machine + framework for animations, see the states example (it lives in the + \c{examples/animation/states} directory). +*/ + |