# Key Listener

Welcome to the svyKeyListener wiki!

## Introduction

svyKeyListener is a simple service to send key strokes from the browser to a callback method executing on the server This allows a developer to handle keystroke events inside the servoy environment. "keylistener" attribute of a component (from Properties view) must be used together with addKeyListener API of the service to get desired effect.

Table of contents

* [svyKeyListener API](#svykeylistener-api)

## svyKeyListener API

| Method                                  | Params                                                                                                                                          |  Return | Description                                                                                                                                  |
| --------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------- | :-----: | -------------------------------------------------------------------------------------------------------------------------------------------- |
| [addKeyListener](#addkeylistener)       | callbackKey:string, callback:Function, \[clearPreviousCallback:boolean], \[delay:boolean], \[regexPattern:boolean], \[regexReplacement:boolean] |         | Registers the listener on the components which have the "keylistener" attribute with the given callbackKey value, to call the given callback |
| [removeKeyListener](#removekeylistener) | callbackKey:string                                                                                                                              | boolean | Removes the listener associated to the given callback key                                                                                    |

### addKeyListener

Registers the listener on the components which have the "keylistener" attribute with the given callbackKey value, to call the given callback. **Params**

| Type     | Name             | Description                                                                                                                                                                                | Required |
| -------- | ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------- |
| string   | callbackKey      | The callback key.                                                                                                                                                                          | Required |
| Function | callback         | The function will be called and passed \[string value, JSEvent event, number keyCode, boolean altKey, boolean ctrlKey, boolean shiftKey, boolean capsLock]                                 | Required |
| boolean  | clearCB          | Specifies if the previously added callback associated to this callback key should be removed.                                                                                              | Optional |
| int      | delay            | Debouncing for callback function. The callback is fired only when the specified delay (milliseconds) has been pass. If "delay" is not specified, a default delay of 1000 ms will be used." | Optional |
| String   | regexPattern     | Javascript regular expression string to modify current value of the component                                                                                                              | Optional |
| String   | regexReplacement | The value that is used to replace the regular expression with in the current value of the component                                                                                        | Optional |

**Returns** void

#### example

On the component(s) you want to register the listener, you need to add a **keylistener** attribute. Let's assume we add the **keylistener** attribute with the value **test** to be used as a callback key:

Then, for instance in the onShow method of the form, you need to associate that callback key to a function:

```javascript
function onShow(firstShow, event) {
	plugins.keyListener.addKeyListener('test', onKey)
}

function onKey(value, event, keyCode, altKey, ctrlKey, shiftKey, capsLock){
        application.output("The new value is "+value);
}
```

The behavior may be altered using optional parameters:

```javascript
function onShow(firstShow, event) {
        // the onKey() will be triggered after 500 ms. The 'blue' string from the input value will be 
        // replaced with 'red' string.
	plugins.keyListener.addKeyListener('test', onKey, false, 500, 'blue', 'red');
}

function onKey(value, event, keyCode, altKey, ctrlKey, shiftKey, capsLock){
        application.output("The new value is "+value);
}
```

### removeKeyListener

Removes the listener associated to the given callback key. Returns true if the listener was removed.

**Params**

| Type   | Name        | Description       | Required |
| ------ | ----------- | ----------------- | -------- |
| string | callbackKey | The callback key. | Required |

**Returns** boolean

#### example

```javascript
function onAction(event) {
	if (plugins.keyListener.removeKeyListener('test')) {
           application.output("Removed the key listener associated to the callback key 'test'");
        }
}
```


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