diff options
Diffstat (limited to 'doc')
-rw-r--r-- | doc/src/declarative/dynamicobjects.qdoc | 48 | ||||
-rw-r--r-- | doc/src/snippets/declarative/dynamicObjects.qml | 30 | ||||
-rw-r--r-- | doc/src/snippets/declarative/flickableScrollbar.qml | 26 |
3 files changed, 74 insertions, 30 deletions
diff --git a/doc/src/declarative/dynamicobjects.qdoc b/doc/src/declarative/dynamicobjects.qdoc index 5cdd768..dc0277d 100644 --- a/doc/src/declarative/dynamicobjects.qdoc +++ b/doc/src/declarative/dynamicobjects.qdoc @@ -132,36 +132,24 @@ do not have an id in QML. \section1 Deleting Objects Dynamically -You should generally avoid dynamically deleting objects that you did not -dynamically create. In many UIs, it is sufficient to set the opacity to 0 or -to move the item off of the edge of the screen. If you have lots of dynamically -created items however, deleting them when they are no longer used will provide -a worthwhile performance benefit. Note that you should never manually delete -items which were dynamically created by QML Elements such as \l{Loader}. - -To manually delete a QML item, call its destroy method. This method has one -argument, which is an approximate delay in milliseconds and which defaults to zero. This -allows you to wait until the completion of an animation or transition. An example: - -\code - Component { - id: fadesOut - Rectangle{ - id: rect - width: 40; height: 40; - NumberAnimation on opacity { from:1; to:0; duration: 1000 } - Component.onCompleted: rect.destroy(1000); - } - } - function createFadesOut(parentItem) - { - var object = fadesOut.createObject(); - object.parent = parentItem; - } -\endcode - -In the above example, the dynamically created rectangle calls destroy as soon as it is created, - but delays long enough for its fade out animation to be played. +In many user interfaces, it is sufficient to set an item's opacity to 0 or +to move the item off the screen instead of deleting the item. If you have +lots of dynamically created items, however, you may receive a worthwhile +performance benefit if unused items are deleted. + +Note that you should never manually delete items that were dynamically created +by QML elements (such as \l Loader). Also, you should generally avoid deleting +items that you did not dynamically create yourself. + +Items can be deleted using the \c destroy() method. This method has an optional +argument (which defaults to 0) that specifies the approximate delay in milliseconds +before the object is to be destroyed. This allows you to wait until the completion of +an animation or transition. An example: + +\snippet doc/src/snippets/declarative/dynamicObjects.qml 0 + +Here, \c Rectangle objects are destroyed one second after they are created, which is long +enough for the \c NumberAnimation to be played before the object is destroyed. */ diff --git a/doc/src/snippets/declarative/dynamicObjects.qml b/doc/src/snippets/declarative/dynamicObjects.qml new file mode 100644 index 0000000..dd55d78 --- /dev/null +++ b/doc/src/snippets/declarative/dynamicObjects.qml @@ -0,0 +1,30 @@ +import Qt 4.7 + +//![0] +Rectangle { + id: rootItem + width: 300 + height: 300 + + Component { + id: rectComponent + + Rectangle { + id: rect + width: 40; height: 40; + color: "red" + + NumberAnimation on opacity { from: 1; to: 0; duration: 1000 } + + Component.onCompleted: rect.destroy(1000); + } + } + + function createRectangle() { + var object = rectComponent.createObject(); + object.parent = rootItem; + } + + Component.onCompleted: createRectangle() +} +//![0] diff --git a/doc/src/snippets/declarative/flickableScrollbar.qml b/doc/src/snippets/declarative/flickableScrollbar.qml new file mode 100644 index 0000000..147751a --- /dev/null +++ b/doc/src/snippets/declarative/flickableScrollbar.qml @@ -0,0 +1,26 @@ +import Qt 4.7 + +//![0] +Rectangle { + width: 200; height: 200 + + Flickable { + id: flickable +//![0] + anchors.fill: parent + contentWidth: image.width; contentHeight: image.height + + Image { id: image; source: "pics/qt.png" } +//![1] + } + + Rectangle { + id: scrollbar + anchors.right: flickable.right + y: flickable.visibleArea.yPosition * flickable.height + width: 10 + height: flickable.visibleArea.heightRatio * flickable.height + color: "black" + } +} +//![1] |