内容

• 特性
• 详细描述
• 用法范例

HistoryState QML Type

The HistoryState type provides a means of returning to a previously active substate. 更多...

导入语句：	import QtQml.StateMachine 6.2
Since:	Qt 5.4
继承：	QAbstractState

• 所有成员列表，包括继承成员

特性

• defaultState : QAbstractState
• historyType : enumeration

详细描述

A history state is a pseudo-state that represents the child state that the parent state was in the last time the parent state was exited. A transition with a history state as its target is in fact a transition to one of the other child states of the parent state. HistoryState is part of Qt State Machine QML API .

使用 defaultState property to set the state that should be entered if the parent state has never been entered.

用法范例

import QtQuick
import QtQml.StateMachine as DSM
Rectangle {
    Button {
        anchors.fill: parent
        id: button
        text: "Press me"
        DSM.StateMachine {
            id: stateMachine
            initialState: parentState
            running: true
            DSM.State {
                id: parentState
                initialState: child2
                onEntered: console.log("parentState entered")
                onExited: console.log("parentState exited")
                DSM.State {
                    id: child1
                    onEntered: console.log("child1 entered")
                    onExited: console.log("child1 exited")
                }
                DSM.State {
                    id: child2
                    onEntered: console.log("child2 entered")
                    onExited: console.log("child2 exited")
                }
                DSM.HistoryState {
                    id: historyState
                    defaultState: child1
                }
                DSM.SignalTransition {
                    targetState: historyState
                    // Clicking the button will cause the state machine to enter the child state
                    // that parentState was in the last time parentState was exited, or the history state's default
                    // state if parentState has never been entered.
                    signal: button.clicked
                }
            }
        }
    }
}
					

By default, a history state is shallow, meaning that it will not remember nested states. This can be configured through the historyType 特性。

另请参阅 StateMachine and State .

特性文档编制

defaultState : QAbstractState

The default state of this history state.

The default state indicates the state to transition to if the parent state has never been entered before.

historyType : enumeration

The type of history that this history state records.

此特性的默认值为 HistoryState .ShallowHistory.

This enum specifies the type of history that a HistoryState records.

• HistoryState .ShallowHistory Only the immediate child states of the parent state are recorded. In this case, a transition with the history state as its target will end up in the immediate child state that the parent was in the last time it was exited. This is the default.
• HistoryState .DeepHistory Nested states are recorded. In this case a transition with the history state as its target will end up in the most deeply nested descendant state the parent was in the last time it was exited.