Text metric: On Display

This handler called when tile needs to be updated. E.g. when last activity time needs to be updated or new payload received and needs to be displayed.

Note: This handler called only for visible tiles. If tile scrolled away, this handler will not be called.
Important: this handler is executed each time in CLEAN mode. This means, that previous call state will be cleaned up (any declared variables and functions from previous call will be purged in subsequent call)!
To pass data between calls and handlers use event.data.

In this handler you can use the following:

app.publish(topic, payload, retained, qos);

Publish payload (String) to topic (String) with specified retained flag (Boolean) and qos (Integer). Example:

app.publish('messages/alert', 'HOT', false, 0);

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app.openUri(uri);

Open specified uri (String) in an external app. uri examples:
- http://www.example.com/page.html
- tel:123
- content://contacts/people/

Usually you don’t want to use it in On Display handler, because On Display executed every time, when tile needs to be updated and this happens quite often.

app.openUri('http://www.example.com');

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event.data

(Any type) Custom runtime user data, bound to this particular metric. You can get/set any data, which you need to be preserved between calls.
The data shared between On Receive, On Display, On Tap handlers. So you can set data in On Receive and use this data later in On Display.

Warning: never pass functions through event.data!
The data NOT preserved between app launches. Usually, because the data is not assigned by default, you want to start your handler’s code with check if data assigned, and then use the data:

In On Receive handler:

if (!event.data) {
    event.data = {};
}
event.data['some flag'] = 
    (event.getLastPayload() == 'something' ? true : false);

In On Display or in On Tap handler:

if (event.data['some flag']) {
    // do something
} else {
    // do something other
}

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event.getSecondsSinceLastActivity()

(Integer) Number of seconds, elapsed since last activity (since payload received):

// blink tile to draw attention, if last payload
// was received more than 60 seconds ago
event.blink = event.getSecondsSinceLastActivity() > 60;

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event.lastActivityString

(String) Text to display at the bottom of tile. By default it contains elapsed time, but you can override it. For example:

event.lastActivityString = 
    event.getSecondsSinceLastActivity() + " seconds ago";

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event.blink

(Boolean) Tile will blink if value of the property is true. Example:

// blink tile if temperature out of range
event.blink =
    (event.getLastPayload() < 20 || event.getLastPayload() > 40);

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event.name

(String) Text to display at the top of the tile. By default it contains metric name. You can override it.

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event.getLastPayload()

(String) Returns last received raw payload. Raw means, that prefix, postfix and any other payload transformations not applied yet (if configured).

// change text color if temperature is below 20 degrees
// and display 'COLD' instead of temperature
if (event.getLastPayload() < 20) {
    event.textColor = '#ffcccc';
    event.text = 'COLD';
} else {
    event.textColor = '#ffffff';
};

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event.text

(String) Main tile text. You can override it. See example from above.

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event.textColor

(HEX String) Main text color. E.g. #ffffcc.

// change text color if temperature is less than 20 degrees
event.textColor = 
    event.getLastPayload() < 20 ? '#ffcccc' : '#ffffff';