HistoryState QML Type

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

• List of all members, including inherited members

Properties

• defaultState : QAbstractState
• historyType : enumeration

Detailed Description

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 The Declarative State Machine Framework.

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

Example Usage

  import QtQuick 2.0
  import QtQml.StateMachine 1.0 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 property.

See also StateMachine and State.

Property Documentation