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4 files changed, 211 insertions, 4 deletions
diff --git a/doc/src/declarative/behaviors-and-states.qdoc b/doc/src/declarative/behaviors-and-states.qdoc new file mode 100644 index 0000000..0815b39 --- /dev/null +++ b/doc/src/declarative/behaviors-and-states.qdoc @@ -0,0 +1,206 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the documentation of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:FDL$ +** 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 Technology Preview License Agreement accompanying +** this package. +** +** GNU Free Documentation License +** Alternatively, this file may be used under the terms of the GNU Free +** Documentation License version 1.3 as published by the Free Software +** Foundation and appearing in the file included in the packaging of this +** file. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ + +/*! +\page qml-behaviors-and-states.html +\title Using QML Behaviors with States + +\section1 Using Behaviors with States + +In some cases you may choose to use a Behavior to animate a property change caused by a state change. While this works well for some situations, in other situations it may lead to unexpected behavior. + +Here's an example that shows the problem: + +\qml +import QtQuick 1.0 + +Rectangle { + width: 400 + height: 400 + + Rectangle { + id: coloredRect + width: 100 + height: 100 + anchors.centerIn: parent + + color: "red" + Behavior on color { + ColorAnimation {} + } + + MouseArea { + id: mouser + anchors.fill: parent + hoverEnabled: true + } + + states: State { + name: "GreenState" + when: mouser.containsMouse + + PropertyChanges { + target: coloredRect + color: "green" + } + } + } +} +\endqml + +Testing the example by quickly and repeatedly moving the mouse in to and out of the colored rectangle shows that the colored rectangle will settle into a green color over time, never returning to full red. This is not what we wanted! The +problem occurs because we have used a Behavior to animate the change in color, and our state change is trigged by the mouse entering or exiting the MouseArea, which is easily interrupted. + +To state the problem more formally, using States and Behaviors together can cause unexpected behavior when: +\list +\o a Behavior is used to animate a property change, specifically when moving from an explicitly defined state back to the implicit base state; and +\o this Behavior can be interrupted to (re-)enter an explicitly defined state. +\endlist + +The problem occurs because of the way the base state is defined for QML: as the "snapshot" state of the application just prior to entering an explicitly defined state. In this case, if we are in the process of animating from green back +to red, and interrupt the animation to return to "GreenState", the base state will include the color in its intermediate, mid-animation form. + +While future versions of QML should be able to handle this situation more gracefully, there are currently several ways to rework your application to avoid this problem. + +1. Use a transition to animate the change, rather than a Behavior. + +\qml +import QtQuick 1.0 + +Rectangle { + width: 400 + height: 400 + + Rectangle { + id: coloredRect + width: 100 + height: 100 + anchors.centerIn: parent + + color: "red" + + MouseArea { + id: mouser + anchors.fill: parent + hoverEnabled: true + } + + states: State { + name: "GreenState" + when: mouser.containsMouse + + PropertyChanges { + target: coloredRect + color: "green" + } + } + + transitions: Transition { + ColorAnimation {} + } + } +} +\endqml + +2. Use a conditional binding to change the property value, rather than a state + +\qml +import QtQuick 1.0 + +Rectangle { + width: 400 + height: 400 + + Rectangle { + id: coloredRect + width: 100 + height: 100 + anchors.centerIn: parent + + color: mouser.containsMouse ? "green" : "red" + Behavior on color { + ColorAnimation {} + } + + MouseArea { + id: mouser + anchors.fill: parent + hoverEnabled: true + } + } +} +\endqml + +3. Use only explicitly defined states, rather than an implicit base state + +\qml +import QtQuick 1.0 + +Rectangle { + width: 400 + height: 400 + + Rectangle { + id: coloredRect + width: 100 + height: 100 + anchors.centerIn: parent + + Behavior on color { + ColorAnimation {} + } + + MouseArea { + id: mouser + anchors.fill: parent + hoverEnabled: true + } + + states: [ + State { + name: "GreenState" + when: mouser.containsMouse + + PropertyChanges { + target: coloredRect + color: "green" + } + }, + State { + name: "RedState" + when: !mouser.containsMouse + + PropertyChanges { + target: coloredRect + color: "red" + } + }] + } +} +\endqml + +*/ diff --git a/src/declarative/util/qdeclarativebehavior.cpp b/src/declarative/util/qdeclarativebehavior.cpp index 41f8fe5..a1321e2 100644 --- a/src/declarative/util/qdeclarativebehavior.cpp +++ b/src/declarative/util/qdeclarativebehavior.cpp @@ -72,7 +72,7 @@ public: /*! \qmlclass Behavior QDeclarativeBehavior - \ingroup qml-animation-transition + \ingroup qml-animation-transition \since 4.7 \brief The Behavior element allows you to specify a default animation for a property change. @@ -91,7 +91,8 @@ public: If a \l{QML States}{state change} has a \l Transition that matches the same property as a Behavior, the \l Transition animation overrides the Behavior for that - state change. + state change. For general advice on using Behaviors to animate state changes, see + \l{Using QML Behaviors with States}. \sa {QML Animation and Transitions}, {declarative/animation/behaviors}{Behavior example}, QtDeclarative */ diff --git a/src/declarative/util/qdeclarativexmllistmodel.cpp b/src/declarative/util/qdeclarativexmllistmodel.cpp index 5af53e6..c79baa4 100644 --- a/src/declarative/util/qdeclarativexmllistmodel.cpp +++ b/src/declarative/util/qdeclarativexmllistmodel.cpp @@ -919,7 +919,7 @@ void QDeclarativeXmlListModel::reload() } else { d->notifyQueryStarted(true); QNetworkRequest req(d->src); - req.setRawHeader("Accept", "application/xml"); + req.setRawHeader("Accept", "application/xml,*/*"); d->reply = qmlContext(this)->engine()->networkAccessManager()->get(req); QObject::connect(d->reply, SIGNAL(finished()), this, SLOT(requestFinished())); QObject::connect(d->reply, SIGNAL(downloadProgress(qint64,qint64)), diff --git a/tests/auto/declarative/qdeclarativexmllistmodel/tst_qdeclarativexmllistmodel.cpp b/tests/auto/declarative/qdeclarativexmllistmodel/tst_qdeclarativexmllistmodel.cpp index af54008..a0e2547 100644 --- a/tests/auto/declarative/qdeclarativexmllistmodel/tst_qdeclarativexmllistmodel.cpp +++ b/tests/auto/declarative/qdeclarativexmllistmodel/tst_qdeclarativexmllistmodel.cpp @@ -418,7 +418,7 @@ void tst_qdeclarativexmllistmodel::headers() QTRY_COMPARE(model->status(), QDeclarativeXmlListModel::Ready); QVariantMap expectedHeaders; - expectedHeaders["Accept"] = "application/xml"; + expectedHeaders["Accept"] = "application/xml,*/*"; QCOMPARE(factory.lastSentHeaders.count(), expectedHeaders.count()); foreach (const QString &header, expectedHeaders.keys()) { |