Image Button

Image Button widget improves the UI of your IoT app communicating the button or device state visually. The widget allows you to turn any image into a button and use custom images for different button states.

Mode

Image Button can operate in these modes:

Push. Set to ON state when pressed, then back to OFF state when released
Switch. Toggles between ON/OFF state each time it is pressed
Page. Opens a specified app page when pressed (requires Plus plan)
QR. Opens phone QR Scanner (requires PRO plan)

How the QR code scanner works

End users will tap on the widget and a code scanner (camera) will open. The camera should be pointed to the code.

Once the code is successfully scanned, its contents will be sent to the hardware in a String format to the specified Datastream. The scanner screen will be closed automatically. A String Datastream should be added to the Device Template to accept these values.

Value of the code is sent as is (not pre-processed or post-processed by Blynk).

In case of scanning an unsupported format, no error will be shown. User would need to close the scanner view (camera) manually.

End-users would need to grant permissions to use the camera on the smartphone OS level. If permission wasn’t granted, a message will be shown to go to settings to enable access to the camera.

Scanner works with these code formats

QR
AZTEC
CODE_39
CODE_39 mod 43
CODE_93
CODE_128
DATA_MATRIX
EAN_8
EAN-13
ITF
PDF_417
UPC_E

Android app can additionally support these formats:

CODABAR
MAXICODE
RSS_14
RSS_EXPANDED
UPC_A
UPC_EAN_EXTENSION

Datastream

Select or create a datastream of data type integer, double, or string. Widget properties (label, color, etc.) are also changed via the datastream, but only for virtual, enumerable, and location pins, not digital and analog pins.

How to process Image Button input on the device

When button is pressed, value is sent and stored into the Blynk.Cloud. After that it's sent to your device.

Reading the Image Button value

For example, if Button Widget is set to Datastream with Virtual Pin V1, you can use such code:

BLYNK_WRITE(V1) // this command is listening when something is written to V1
{
  int pinValue = param.asInt(); // assigning incoming value from pin V1 to a variable
  
  if (pinValue == 1){
   // do something when button is pressed;
  } else if (pinValue == 0) {
   // do something when button is released;
  }
  
  Serial.print("V1 button value is: "); // printing value to serial monitor
  Serial.println(pinValue);
}

Changing Image Button state

You can also update the state of the button from hardware.

Blynk.virtualWrite(vPin, HIGH);

Blynk.virtualWrite(vPin, 1);

Don't put Blynk.virtualWrite()into the void loop() as it can cause a flood of messages and your hardware will be disconnected. Send such updates only when necessary, use flags, or timers.

Sketch: Basic Sketch

Sketch: Physical Button Interrupt

Sketch: Physical Button Poll

Sketch: Physical Button State Sync

Change Image Button Properties

You can change certain properties of the Widget from your hardware. For that, use this command:

Blynk.setProperty(vPin, "widgetProperty", "propertyValue");

Where:

vPin is: virtual pin number the widget is assigned to
widgetProperty: property you want to change
propertyValue: value of the property you want to change

Don't put Blynk.setProperty()into the void loop() as it can cause a flood of messages and your hardware will be disconnected. Send such updates only when necessary, or use timers.

Properties you can change

You can change the properties onImageUrl, offImageUrl, label, isDisabled, isHidden, and page of the widget from your hardware, or via an HTTP API. The URL must be encoded, so spaces in labels must be replaced with %20, and color hexadecimal values in the HTTP API URL must include the hash # character urlencoded as %23.

Change On/Off images

Blynk.setProperty(V1, "onImageUrl", "URL");
Blynk.setProperty(V1, "offImageUrl", "URL");

Blynk.setProperty(V1, "label", "Toggle");

Disable/Enable

Widget will be greyed out on UI and users won't be able to tap on it.

Blynk.setProperty(V1, "isDisabled", true);

Show/Hide

Widget will be hidden from dashboard. Design your UI so that it doesn't look weird when there is no widget.

Blynk.setProperty(V1, "isHidden", true);

Change Page Target

This command will set which page should open when the button is pressed. PageId can be found in the mobile app in developer mode: Toolbox -> Pages

Blynk.setProperty(V1, "page", "pageId");

Updates the Datastream Property and all assigned Widgets

GET https://{server_address}/external/api/update/property?token={your 32 char token}&pin={your vPin}&{property}={value}

The endpoint allows you to update the Datastream Property value via GET request. All widgets (both web and mobile) that are assigned to this datastream will inherit this property. The Datastream Property is persistent and will be stored forever until you change it with another value. In order to clear the property you need to clear the device data in device actions menu.

Example: https://blynk.cloud/external/api/update/property?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&pin=V2&label=My%20Label

https://blynk.cloud/external/api/update/property?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&pin=V1&offImageUrl=https://mechatronicsolutionsllc.com/Blynk%20image%20beat%20.png

https://blynk.cloud/external/api/update/property?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&pin=V1&isDisabled=true

https://blynk.cloud/external/api/update/property?token=GVki9IC70vb3IqvsV0YD3el4y0OpneL1&pin=V1&page={pageID}

Path Parameters

Name	Type	Description
{server address}*	string	Get from the bottom right of your Blynk console. More information.

Name

Type

Description

{server address}*

string

Get from the bottom right of your Blynk console. More information.

Query Parameters

Name Type Description

Name	Type	Description
token*	string	Device auth token from Device info
pin*	string	The datastream virtual pin (should start with "v")
{property}	string	The property of the widget you want to update: `onLabel`, `offLabel`, `label`, `color`, `isDisabled`, `isHidden`, and `page`
onImageUrl	string	the image URL, should be urlencoded
offImageUrl	string	the image URL, should be urlencoded
label	string	the text used as widget label
isDisabled	string	true or false
isHidden	string	true or false
pageID	string	pageID

token*

string

Device auth token from Device info

pin*

string

The datastream virtual pin (should start with "v")

{property}

string

The property of the widget you want to update: onLabel, offLabel, label, color, isDisabled, isHidden, and page

onImageUrl

string

the image URL, should be urlencoded

offImageUrl

string

the image URL, should be urlencoded

label

string

the text used as widget label

isDisabled

string

true or false

isHidden

string

true or false

pageID

string

pageID

{"error":{"message":"Invalid token."}}

Sync to the latest known state

You can update your hardware to the latest datastream value from Blynk.Cloud after your hardware went offline, and then came online again. Use Blynk.syncVirtual() to update a single virtual pin, or Blynk.syncAll() to update all virtual pins. See State Syncing for more details.

BLYNK_CONNECTED() { 
  // Called when hardware is connected to Blynk.Cloud  

  // get the latest value for V1
  Blynk.syncVirtual(V1); 

  // Request Blynk server to re-send latest values for all pins
  Blynk.syncAll()
}

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Last updated 1 year ago

Image Button

Mode

How the QR code scanner works

Scanner works with these code formats

Datastream

How to process Image Button input on the device

Reading the Image Button value

Changing Image Button state

Change Image Button Properties

Properties you can change

Change On/Off images

Set a custom label for the widget

Disable/Enable

Show/Hide

Change Page Target

Change widget properties via HTTPs API

Updates the Datastream Property and all assigned Widgets

Path Parameters

Query Parameters

Sync to the latest known state