照片查看器 演示以下 Qt Quick 特征：
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In the Photo Viewer app, we use the following custom types that are each defined in a separate .qml file:
AlbumDelegate.qml
BusyIndicator.qml
Button.qml
EditableButton.qml
PhotoDelegate.qml
ProgressBar.qml
RssModel.qml
Tag.qml
To use the custom types, we add an import statement to the main QML file, main.qml, that imports the folder called
PhotoViewerCore
where the types are located:
import "PhotoViewerCore"
在 main.qml，使用 ApplicationWindow Qt Quick Control 以创建 APP 主窗口：
ApplicationWindow { id: mainWindow visible: true
使用 ListModel type with ListElement types to display photo albums:
ListModel {
id: photosModel
ListElement { tag: "Flowers" }
ListElement { tag: "Wildlife" }
ListElement { tag: "Prague" }
}
List elements are defined like other QML types except that they contain a collection of
role
definitions instead of properties. Roles both define how the data is accessed and include the data itself. For each list element, we use the
tag
role to specify the photos to download.
A
DelegateModel
type is used together with the
Package
type to provide delegates to multiple views. The
model
property holds the model providing data for the delegate model and the
delegate
property specifies the template defining each item instantiated by a view:
DelegateModel { id: albumVisualModel; model: photosModel; delegate: AlbumDelegate {} }
使用 GridView type to lay out the albums as a grid:
GridView {
id: albumView; width: parent.width; height: parent.height; cellWidth: 210; cellHeight: 220
model: albumVisualModel.parts.album; visible: albumsShade.opacity != 1.0
}
model
property references the package name
album
that we specify in AlbumDelegate.qml. We use the
Package
type to allow the photos to move between different views. The
Package
contains the named items
browser
,
fullscreen
，和
album
:
Package {
Item {
Package.name: 'browser'
GridView {
id: photosGridView; model: visualModel.parts.grid; width: mainWindow.width; height: mainWindow.height - 21
x: 0; y: 21; cellWidth: 160; cellHeight: 153; interactive: false
onCurrentIndexChanged: photosListView.positionViewAtIndex(currentIndex, ListView.Contain)
}
}
Item {
Package.name: 'fullscreen'
ListView {
id: photosListView; model: visualModel.parts.list; orientation: Qt.Horizontal
width: mainWindow.width; height: mainWindow.height; interactive: false
onCurrentIndexChanged: photosGridView.positionViewAtIndex(currentIndex, GridView.Contain)
highlightRangeMode: ListView.StrictlyEnforceRange; snapMode: ListView.SnapOneItem
}
}
Item {
Package.name: 'album'
id: albumWrapper; width: 210; height: 220
The named items are used as the delegates by the views that reference the special DelegateModel::parts property to select the model that provides the chosen delegate.
使用 ListView type to lay out albums in other views:
ListView { anchors.fill: parent; model: albumVisualModel.parts.browser; interactive: false }
ListView { anchors.fill: parent; model: albumVisualModel.parts.fullscreen; interactive: false }
We use the PhotoDelegate custom type that is specified in PhotoDelegate.qml to display photos. We use a Package type to lay out the photos either in a stack, list, or a grid:
Package { Item { id: stackItem; Package.name: 'stack'; width: 160; height: 153; z: stackItem.PathView.z } Item { id: listItem; Package.name: 'list'; width: mainWindow.width + 40; height: 153 } Item { id: gridItem; Package.name: 'grid'; width: 160; height: 153 }
The photos are rotated at random angles by using the
Math.random()
JavaScript 方法：
Item {
width: 160; height: 153
Item {
id: photoWrapper
property double randomAngle: Math.random() * (2 * 6 + 1) - 6
property double randomAngle2: Math.random() * (2 * 6 + 1) - 6
x: 0; y: 0; width: 140; height: 133
z: stackItem.PathView.z; rotation: photoWrapper.randomAngle
使用 BorderImage type to create borders for the images:
BorderImage {
anchors {
fill: originalImage.status == Image.Ready ? border : placeHolder
leftMargin: -6; topMargin: -6; rightMargin: -8; bottomMargin: -8
}
source: 'images/box-shadow.png'
border.left: 10; border.top: 10; border.right: 10; border.bottom: 10
}
In AlbumDelegate.qml, we use the DelegateModel to provide the PhotoDelegate delegate to the RssModel model:
DelegateModel {
id: visualModel; delegate: PhotoDelegate { }
model: RssModel { id: rssModel; tags: tag }
}
In RssModel.qml, we use an XmlListModel type as a data source for Package objects to download photos from the selected feeds:
import QtQuick.XmlListModel 2.0 XmlListModel { property string tags : "" function encodeTags(x) { return encodeURIComponent(x.replace(' ',',')); }
使用
tags
custom property to specify which photos to download. The
encodeTags
custom function uses the
encodeURIComponent
JavaScript method to ensure that the requests to the server are correctly formatted.
使用
source
property to fetch photos that have the specified tags attached from public Flickr feeds:
source: "http://api.flickr.com/services/feeds/photos_public.gne?"+(tags ? "tags="+encodeTags(tags)+"&" : "")
query: "/feed/entry"
namespaceDeclarations: "declare default element namespace 'http://www.w3.org/2005/Atom';"
query
property specifies that the
XmlListModel
generates a model item for each feed entry.
namespaceDeclarations
property specifies that the requested document uses the namespace
http://www.w3.org/2005/Atom
, which is declared as the default namespace.
使用
XmlRole
type to specify the model item attributes. Each model item has the
title
,
content
，和
hq
attributes that match the values of the corresponding feed entry:
XmlRole { name: "title"; query: "title/string()" }
XmlRole { name: "content"; query: "content/string()" }
XmlRole { name: "hq"; query: "link[@rel='enclosure']/@href/string()" }
When users select the Edit button, the album labels are flipped from their front side to their back side and the text on them changes from album name to 移除 .
In AlbumDelegate.qml, we use the Tag custom type to specify the text to display on the front and back sides of album labels:
Tag {
anchors { horizontalCenter: parent.horizontalCenter; bottom: parent.bottom; bottomMargin: 10 }
frontLabel: tag; backLabel: qsTr("Remove"); flipped: mainWindow.editMode
onTagChanged: rssModel.tags = tag
onBackClicked: if (mainWindow.editMode) photosModel.remove(index);
}
onTagChanged
signal handler is used to change the tag based on which the model is populated. The
onBackClicked
signal handler is used to remove the album.
在 Tag.qml，使用 可翻转 type with custom properties and signals to create the labels:
Flipable { id: flipable property alias frontLabel: frontButton.label property alias backLabel: backButton.label property int angle: 0 property int randomAngle: Math.random() * (2 * 6 + 1) - 6 property bool flipped: false signal frontClicked signal backClicked signal tagChanged(string tag)
front
property holds the EditableButton custom type that enables users to edit the label text:
front: EditableButton {
id: frontButton; rotation: flipable.randomAngle
anchors { centerIn: parent; verticalCenterOffset: -20 }
onClicked: flipable.frontClicked()
onLabelChanged: flipable.tagChanged(label)
}
back
property holds the
Button
custom type that is used to remove the album:
back: Button {
id: backButton; tint: "red"; rotation: flipable.randomAngle
anchors { centerIn: parent; verticalCenterOffset: -20 }
onClicked: flipable.backClicked()
}
In AlbumDelegate.qml, we use a
PathView
type to lay out the photos provided by the
visualModel.parts.stack
model on a path that has the form of a stack:
PathView {
id: photosPathView; model: visualModel.parts.stack; pathItemCount: 5
visible: !busyIndicator.visible
anchors.centerIn: parent; anchors.verticalCenterOffset: -30
path: Path {
PathAttribute { name: 'z'; value: 9999.0 }
PathLine { x: 1; y: 1 }
PathAttribute { name: 'z'; value: 0.0 }
}
}
path
property holds the
Path
type that defines the path used by the
PathView
。
PathAttribute
types are used to set a range of
0
to
9999
为
z
attribute. This way, the path creates a stack of album photos. Because each PhotoDelegate is slightly rotated at a random angle, this results in a realistic-looking stack of photos.
We use a busy indicator and a progress bar to indicate activity while Flickr feeds and photos are being loaded.
In AlbumDelegate.qml, we use the
BusyIndicator
custom type and the
on
custom property to display a rotating image while the Flickr feed is being loaded:
BusyIndicator {
id: busyIndicator
anchors { centerIn: parent; verticalCenterOffset: -20 }
on: rssModel.status != XmlListModel.Ready
}
In PhotoDelegate.qml, we use them to indicate activity while a photo is being loaded:
BusyIndicator { anchors.centerIn: parent; on: originalImage.status != Image.Ready }
定义
BusyIndicator
类型在
BusyIndicator.qml
. We use an
图像
type to display an image and apply a
NumberAnimation
to its
rotation
property to rotate the image in an infinite loop:
Image { id: container property bool on: false source: "images/busy.png"; visible: container.on NumberAnimation on rotation { running: container.on; from: 0; to: 360; loops: Animation.Infinite; duration: 1200 } }
在 APP 中，还可以使用 BusyIndicator 类型从 Qt Quick Controls 模块。
在 main.qml，使用
ProgressBar
custom type to indicate progress while a high quality version of a photo is being opened on full screen:
ProgressBar {
progress: mainWindow.downloadProgress; width: parent.width; height: 4
anchors.bottom: parent.bottom; opacity: mainWindow.imageLoading; visible: opacity != 0.0
}
定义
ProgressBar
类型在
ProgressBar.qml
. We use a
Rectangle
type to create the progress bar and apply a
NumberAnimation
to its
opacity
property to change the color of the bar from black to white as data loading proceeds:
Item { id: container property real progress: 0 Behavior on opacity { NumberAnimation { duration: 600 } } Rectangle { anchors.fill: parent; color: "black"; opacity: 0.5 } Rectangle { id: fill; color: "white"; height: container.height width: container.width * container.progress } }
在 APP 中，还可以使用 ProgressBar 类型从 Qt Quick Controls 模块。
The example application is translated into German and French. The translated strings are loaded at runtime according to the current locale.
使用 Column type in main.qml to position buttons for adding and editing albums and exiting the application:
Column {
spacing: 20; anchors { bottom: parent.bottom; right: parent.right; rightMargin: 20; bottomMargin: 20 }
Button {
id: newButton; label: qsTr("Add"); rotation: 3
anchors.horizontalCenter: parent.horizontalCenter
onClicked: {
mainWindow.editMode = false
photosModel.append( { tag: "" } )
albumView.positionViewAtIndex(albumView.count - 1, GridView.Contain)
}
}
Button {
id: deleteButton; label: qsTr("Edit"); rotation: -2;
onClicked: mainWindow.editMode = !mainWindow.editMode
anchors.horizontalCenter: parent.horizontalCenter
}
Button {
id: quitButton; label: qsTr("Quit"); rotation: -2;
onClicked: Qt.quit()
anchors.horizontalCenter: parent.horizontalCenter
}
}
使用 qsTr() command to mark the button labels translatable.
使用
lupdate()
tool to generate the translation source files and the
lrelease()
tool to convert the translated strings to the QM files used by the application at runtime. These files are stored in the
i18n
目录。
To make the application aware of the translations, we add code to the
main()
function in the main.cpp file. The code creates a
QTranslator
object, loads a translation according to the current locale at runtime, and installs the translator object into the application:
int main(int argc, char *argv[]) { QGuiApplication app(argc, argv); QTranslator qtTranslator; qtTranslator.load("qml_" + QLocale::system().name(), ":/i18n/"); app.installTranslator(&qtTranslator);
文件：
另请参阅 QML 应用程序 .