Class “Listeners”
Objects of the type Listeners provide methods to manage listeners and trigger events. They encapsulate the tabris event system in a way that is more convenient to use with TypeScript and the ES2017 async/await feature.
| TypeScript type | Listeners<EventData extends {target: object}> extends Object |
| Constructor | public |
| Singleton | No |
| Namespace | tabris |
| Direct subclasses | ChangeListeners |
| JSX support | No |
Constructor
new Listeners(target, type)
| Parameter | Type | Optional | Description |
|---|---|---|---|
| target | object |
No | |
| type | string |
No |
Methods
addListener(listener)
Registers a listener to be notified by new events. Each listener can only be added once. Returns the target object. Instances of Listeners can also be called directly as a function to register a new listener. I.e. widget.onResize(listener); is the same as widget.onResize.addListener(listener); It is also the same as widget.on('resize', listener');, but with better TypeScript support.
| Parameter | Type | Optional | Description |
|---|---|---|---|
| listener | (event: EventObject) => void |
No |
Returns this.target
once(listener)
Notifies the given listener the next time an event is issued, but not afterwards. Returns the target object.
| Parameter | Type | Optional | Description |
|---|---|---|---|
| listener | (event: EventObject) => void |
No |
Returns this.target
promise()
Returns a promise that resolves the next time an event is issued. The dispatched event object will be used as the resolved value.
Returns Promise
removeListener(listener)
Deregisters a listener, it will not be notified of future events. Returns the target object.
| Parameter | Type | Optional | Description |
|---|---|---|---|
| listener | (event: EventObject) => void |
No |
Returns this.target
trigger()
Issues a plain event object to all registered listeners with a newly constructed event object.
Returns this.target
trigger(eventData?)
Issues an event object to all registered listeners. If an uninitialized (not previously issued) instance of EventObject is given as the argument it will be issued directly as-is. Any other type of object (including an already initialized/previously issued event object) will be copied to create a new event object. This allows for simple event re-routing.
| Parameter | Type | Optional | Description |
|---|---|---|---|
| eventData | object |
Yes |
Returns this.target
Properties
target
The object that issues the events, e.g. a widget.
| Type | object |
| Settable | No |
| Change events | Yes |
type
The event type. This value will be set in the type field of the event object given to the listener. It is the same value used by the on and trigger methods.
| Type | string |
| Settable | No |
| Change events | Yes |
Change Events
typeChanged
Fired when the type property has changed.
| Parameter | Type | Description |
|---|---|---|
| value | string |
The new value of type. |
targetChanged
Fired when the target property has changed.
| Parameter | Type | Description |
|---|---|---|
| value | object |
The new value of target. |
