new HardwareButtons()
Gecko code in b2g/chrome/content/shell.js sends mozChromeEvents
when the user presses or releases a hardware button such as Home, Sleep,
and Volume Up and Down.
This module listens for those low-level mozChromeEvents, processes them
and generates higher-level events to handle autorepeat on the volume keys
long presses on Home and Sleep, and the Home+Sleep key combination.
Other system app modules should listen for the high-level button events
generated by this module.
The low-level input events processed by this module have type set
to mozChromeEvent and detail.type set to one of:
- home-button-press
- home-button-release
- sleep-button-press
- sleep-button-release
- volume-up-button-press
- volume-up-button-release
- volume-down-button-press
- volume-down-button-release
The high-level events generated by this module are simple Event objects
that are not cancelable and do not bubble. The are dispatched at the
window object. The type property is set to one of these:
| Event Type | Meaning |
|---|---|
| home | short press and release of home button |
| holdhome | long press and hold of home button |
| sleep | short press and release of sleep button |
| wake | sleep or home pressed while sleeping |
| holdsleep | long press and hold of sleep button |
| volumeup | volume up pressed and released or autorepeated |
| volumedown | volume down pressed and released or autorepeated |
| home+sleep | home and sleep pressed at same time (used for screenshots) |
Because these events are fired at the window object, they cannot be
captured. Many modules listen for the home event. Those that want
to respond to it and prevent others from responding should callstopImmediatePropagation(). Overlays that want to prevent the window
manager from showing the homescreen on the home event should call that
method. Note, however, that this only works for scripts that run and
register their event handlers before AppWindowManager does.
As of the implementation itself, we process events with a
finite state machine.
Each state object has a process() method for handling events.
And optionally has enter() and exit() methods called when the FSM
enters and exits that state.
Example
var hardwareButtons = new HardwareButtons();
hardwareButtons.start(); // Attach the event listeners.
hardwareButtons.stop(); // Deattach the event listeners.Members
-
HOLD_INTERVAL :Number
-
How long for press and hold Home or Sleep.
-
REPEAT_DELAY :Number
-
How long before volume autorepeat begins.
-
REPEAT_INTERVAL :Number
-
How fast the autorepeat is.
Methods
-
handleEvent(evt)
-
Handle events from Gecko.
Parameters:
Name Type Description evt Object Event.
-
publish(type)
-
Dispatch a high-level event of the specified type.
Parameters:
Name Type Description type String name of the event.
-
setState(s, type)
-
Transit the FSM to a new state.
Parameters:
Name Type Description s String Keyword of the new state to switch to.
type String Name of the event to handle
-
start()
-
Start listening to events from Gecko and FSM.
-
stop()
-
Stop listening to events. Must call before throwing away the instance
to avoid memory leaks.