StackView QML Type

Provides a stack-based navigation model. 更多...

import 语句：	import QtQuick.Controls 2.15
Since:	Qt 5.7
继承：	Control

所有成员列表，包括继承成员

特性

busy : bool
currentItem : Item
depth : int
empty : bool
initialItem : var
popEnter : Transition
popExit : Transition
pushEnter : Transition
pushExit : Transition
replaceEnter : Transition
replaceExit : Transition

附加特性

index : int
status : enumeration
view : StackView
visible : bool

附加信号

activated ()
activating ()
deactivated ()
deactivating ()
removed ()

方法

void clear ( transition )
Item find ( callback , behavior )
Item get ( index , behavior )
Item pop ( item , operation )
Item push ( item , properties , operation )
Item replace ( target , item , properties , operation )

详细描述

StackView can be used with a set of inter-linked information pages. For example, an email application with separate views to list the latest emails, view a specific email, and list/view the attachments. The email list view is pushed onto the stack as users open an email, and popped out as they choose to go back.

The following snippet demonstrates a simple use case, where the mainView is pushed onto and popped out of the stack on relevant button click:

ApplicationWindow {
    title: qsTr("Hello World")
    width: 640
    height: 480
    visible: true
    StackView {
        id: stack
        initialItem: mainView
        anchors.fill: parent
    }
    Component {
        id: mainView
        Row {
            spacing: 10
            Button {
                text: "Push"
                onClicked: stack.push(mainView)
            }
            Button {
                text: "Pop"
                enabled: stack.depth > 1
                onClicked: stack.pop()
            }
            Text {
                text: stack.depth
            }
        }
    }
}

Using StackView in an Application

Using StackView in an application is as simple as adding it as a child to a Window. The stack is usually anchored to the edges of the window, except at the top or bottom where it might be anchored to a status bar, or some other similar UI component. The stack can then be used by invoking its navigation methods. The first item to show in the StackView is the one that was assigned to initialItem , or the topmost item if initialItem is not set.

StackView supports three primary navigation operations: push() , pop() ，和 replace() . These correspond to classic stack operations where "push" adds an item to the top of a stack, "pop" removes the top item from the stack, and "replace" is like a pop followed by a push, which replaces the topmost item with the new item. The topmost item in the stack corresponds to the one that is currently visible on screen. Logically, "push" navigates forward or deeper into the application UI, "pop" navigates backward, and "replace" replaces the currentItem .

Pushing Items

In the following animation, three Label controls are pushed onto a stack view with the push() 函数：

The stack now contains the following items: [A, B, C] .

注意： When the stack is empty, a push() operation will not have a transition animation because there is nothing to transition from (typically on application start-up).

Popping Items

Continuing on from the example above, the topmost item on the stack is removed with a call to pop() :

The stack now contains the following items: [A, B] .

注意： A pop() operation on a stack with depth 1 or 0 does nothing. In such cases, the stack can be emptied using the clear() 方法。

Unwinding Items via Pop

Sometimes, it is necessary to go back more than a single step in the stack. For example, to return to a "main" item or some kind of section item in the application. In such cases, it is possible to specify an item as a parameter for pop() . This is called an "unwind" operation, where the stack unwinds till the specified item. If the item is not found, stack unwinds until it is left with one item, which becomes the currentItem . To explicitly unwind to the bottom of the stack, it is recommended to use pop(null) , although any non-existent item will do.

In the following animation, we unwind the stack to the first item by calling pop(null) :

The stack now contains a single item: [A] .

Replacing Items

In the following animation, we replace the topmost item with D :

The stack now contains the following items: [A, B, D] .

Deep Linking

Deep linking means launching an application into a particular state. For example, a newspaper application could be launched into showing a particular article, bypassing the topmost item. In terms of StackView, deep linking means the ability to modify the state of the stack, so much so that it is possible to push a set of items to the top of the stack, or to completely reset the stack to a given state.

The API for deep linking in StackView is the same as for basic navigation. Pushing an array instead of a single item adds all the items in that array to the stack. The transition animation, however, is applied only for the last item in the array. The normal semantics of push() apply for deep linking, that is, it adds whatever is pushed onto the stack.

注意： Only the last item of the array is loaded. The rest of the items are loaded only when needed, either on subsequent calls to pop or on request to get an item using get() .

This gives us the following result, given the stack [A, B, C]:

push([D, E, F]) => [A, B, C, D, E, F] - "push" transition animation between C and F
replace([D, E, F]) => [A, B, D, E, F] - "replace" transition animation between C and F
clear() followed by push([D, E, F]) => [D, E, F] - no transition animation for pushing items as the stack was empty.

Finding Items

An Item for which the application does not have a reference can be found by calling find() . The method needs a callback function, which is invoked for each item in the stack (starting at the top) until a match is found. If the callback returns true , find() stops and returns the matching item, otherwise null 被返回。

The code below searches the stack for an item named "order_id" and unwinds to that item.

stackView.pop(stackView.find(function(item) {
    return item.name == "order_id";
}));

You can also get to an item in the stack using get(index) .

previousItem = stackView.get(myItem.StackView.index - 1));

过渡

For each push or pop operation, different transition animations are applied to entering and exiting items. These animations define how the entering item should animate in, and the exiting item should animate out. The animations can be customized by assigning different Transition s for the pushEnter , pushExit , popEnter , popExit , replaceEnter ，和 replaceExit properties of StackView.

注意： The transition animations affect each others' transitional behavior. Customizing the animation for one and leaving the other may give unexpected results.

The following snippet defines a simple fade transition for push and pop operations:

StackView {
    id: stackview
    anchors.fill: parent
    pushEnter: Transition {
        PropertyAnimation {
            property: "opacity"
            from: 0
            to:1
            duration: 200
        }
    }
    pushExit: Transition {
        PropertyAnimation {
            property: "opacity"
            from: 1
            to:0
            duration: 200
        }
    }
    popEnter: Transition {
        PropertyAnimation {
            property: "opacity"
            from: 0
            to:1
            duration: 200
        }
    }
    popExit: Transition {
        PropertyAnimation {
            property: "opacity"
            from: 1
            to:0
            duration: 200
        }
    }
}

注意： Using anchors on the items added to a StackView is not supported. Typically push, pop, and replace transitions animate the position, which is not possible when anchors are applied. Notice that this only applies to the root of the item. Using anchors for its children works as expected.

Item Ownership

StackView only takes ownership of items that it creates itself. This means that any item pushed onto a StackView will never be destroyed by the StackView; only items that StackView creates from 组件 or URLs are destroyed by the StackView. To illustrate this, the messages in the example below will only be printed when the StackView is destroyed, not when the items are popped off the stack:

Component {
    id: itemComponent
    Item {
        Component.onDestruction: print("Destroying second item")
    }
}
StackView {
    initialItem: Item {
        Component.onDestruction: print("Destroying initial item")
    }
    Component.onCompleted: push(itemComponent.createObject(window))
}

However, both of the items created from the URL and Component in the following example will be destroyed by the StackView when they are popped off of it:

Component {
    id: itemComponent
    Item {
        Component.onDestruction: print("Destroying second item")
    }
}
StackView {
    initialItem: "Item1.qml"
    Component.onCompleted: push(itemComponent)
}

Size

StackView does not inherit an implicit size from items that are pushed onto it. This means that using it as the contentItem 的 Dialog , for example, will not work as expected:

Dialog {
    StackView {
        initialItem: Rectangle {
            width: 200
            height: 200
            color: "salmon"
        }
    }
}

There are several ways to ensure that StackView has a size in this situation:

Set implicitWidth and implicitHeight on the StackView itself.
Set implicitWidth and implicitHeight 在 Rectangle .
Set contentWidth and contentHeight on the Dialog.
Give the Dialog a size.

另请参阅 Customizing StackView , 导航控件 , 容器控件，和 Focus Management in Qt Quick Controls .

特性文档编制

[read-only] busy : bool

This property holds whether a transition is running.

[read-only] currentItem : Item

This property holds the current top-most item in the stack.

[read-only] depth : int

This property holds the number of items currently pushed onto the stack.

[read-only] empty : bool

This property holds whether the stack is empty.

该特性在 QtQuick.Controls 2.3 (Qt 5.10) 引入。

另请参阅 depth .

initialItem : var

This property holds the initial item that should be shown when the StackView is created. The initial item can be an Item , Component ，或 url . Specifying an initial item is equivalent to:

Component.onCompleted: stackView.push(myInitialItem)

另请参阅 push() .

popEnter : Transition

This property holds the transition that is applied to the item that enters the stack when another item is popped off of it.

另请参阅 Customizing StackView .

popExit : Transition

This property holds the transition that is applied to the item that exits the stack when the item is popped off of it.

另请参阅 Customizing StackView .

pushEnter : Transition

This property holds the transition that is applied to the item that enters the stack when the item is pushed onto it.

另请参阅 Customizing StackView .

pushExit : Transition

This property holds the transition that is applied to the item that exits the stack when another item is pushed onto it.

另请参阅 Customizing StackView .

replaceEnter : Transition

This property holds the transition that is applied to the item that enters the stack when another item is replaced by it.

另请参阅 Customizing StackView .

replaceExit : Transition

This property holds the transition that is applied to the item that exits the stack when it is replaced by another item.

另请参阅 Customizing StackView .

附加特性文档编制

[read-only] StackView.index : int

This attached property holds the stack index of the item it's attached to, or -1 if the item is not in a stack.

[read-only] StackView.status : enumeration

This attached property holds the stack status of the item it's attached to, or StackView.Inactive if the item is not in a stack.

Available values:

常量	描述
`StackView.Inactive`	The item is inactive (or not in a stack).
`StackView.Deactivating`	The item is being deactivated (popped off).
`StackView.Activating`	The item is being activated (becoming the current item).
`StackView.Active`	The item is active, that is, the current item.

[read-only] StackView.view : StackView

This attached property holds the stack view of the item it's attached to, or null if the item is not in a stack.

StackView.visible : bool

This attached property holds the visibility of the item it's attached to. The value follows the value of Item::visible .

默认情况下， StackView shows incoming items when the enter transition begins, and hides outgoing items when the exit transition ends. Setting this property explicitly allows the default behavior to be overridden, making it possible to keep items that are below the top-most item visible.

注意： The default transitions of most styles slide outgoing items outside the view, and may also animate their opacity. In order to keep a full stack of items visible, consider customizing the transitions so that the items underneath can be seen.

StackView {
    id: stackView
    property real offset: 10
    width: 100; height: 100
    initialItem: Component {
        id: page
        Rectangle {
            property real pos: StackView.index * stackView.offset
            property real hue: Math.random()
            color: Qt.hsla(hue, 0.5, 0.8, 0.6)
            border.color: Qt.hsla(hue, 0.5, 0.5, 0.9)
            StackView.visible: true
        }
    }
    pushEnter: Transition {
        id: pushEnter
        ParallelAnimation {
            PropertyAction { property: "x"; value: pushEnter.ViewTransition.item.pos }
            NumberAnimation { properties: "y"; from: pushEnter.ViewTransition.item.pos + stackView.offset; to: pushEnter.ViewTransition.item.pos; duration: 400; easing.type: Easing.OutCubic }
            NumberAnimation { property: "opacity"; from: 0; to: 1; duration: 400; easing.type: Easing.OutCubic }
        }
    }
    popExit: Transition {
        id: popExit
        ParallelAnimation {
            PropertyAction { property: "x"; value: popExit.ViewTransition.item.pos }
            NumberAnimation { properties: "y"; from: popExit.ViewTransition.item.pos; to: popExit.ViewTransition.item.pos + stackView.offset; duration: 400; easing.type: Easing.OutCubic }
            NumberAnimation { property: "opacity"; from: 1; to: 0; duration: 400; easing.type: Easing.OutCubic }
        }
    }
    pushExit: Transition {
        id: pushExit
        PropertyAction { property: "x"; value: pushExit.ViewTransition.item.pos }
        PropertyAction { property: "y"; value: pushExit.ViewTransition.item.pos }
    }
    popEnter: Transition {
        id: popEnter
        PropertyAction { property: "x"; value: popEnter.ViewTransition.item.pos }
        PropertyAction { property: "y"; value: popEnter.ViewTransition.item.pos }
    }
}

This property was introduced in QtQuick.Controls 2.2 (Qt 5.9).