Accessing Publish and Subscribe from QML

QML

Two ValueSpaceSubscriber instances are created, one for each of the battery values. We give each object a unique id so that we can reference it from elsewhere in the QML. We set the path properties to the Value Space path of the keys. Finally we set the notify properties to true to enable the emission of change notification signals.

        ValueSpaceSubscriber {
            id: batteryCharge
            path: "/power/battery/charge"
        }
        ValueSpaceSubscriber {
            id: batteryCharging
            path: "/power/battery/charging"
        }

The default state of the rectangle used to visualize the battery charge uses the charge property of our BatteryCharge class in the expression for its height.

            id: visualCharge
            x: 12
            y: 22 + 196 - height
            width: 76
            height: 196 * batteryCharge.value / 100
            clip: true
            color: "green"

When the battery charge changes the height of the rectangle will automatically change.

Next we define two additional states. The low state is entered when the battery charge drops below 25% and the battery is not being recharged. When in this state the color is set to red.

            State {
                name: "low"
                when: batteryCharge.value < 25 && !batteryCharging.value
                PropertyChanges {
                    target: visualCharge
                    color: "red"
                }
            }

The charging state is entered when the battery is being recharged. When in this state a particle effect animation is enabled.

            State {
                name: "charging"
                when: batteryCharging.value
                PropertyChanges {
                    target: Bubbles
                    count: batteryCharge.value / 5
                    emissionRate: 5
                }
            },