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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:
  1. 1.
    Push. Set to ON state when pressed, then back to OFF state when released
  2. 2.
    Switch. Toggles between ON/OFF state each time it is pressed
  3. 3.
    Page. Opens a specified app page when pressed (requires Plus plan)
  4. 4.
    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);
}
Sketch: Basic Sketch​
​

Changing Image Button state

You can also update the state of the button from hardware.
Blynk.virtualWrite(vPin, HIGH);
or
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.

​

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");

Set a custom label for the widget

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");

Change widget properties via HTTPs API

get
https://{server_address}
/external/api/update/property?token={your 32 char token}&pin={your vPin}&{property}={value}
Updates the Datastream Property and all assigned Widgets

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 modified 4mo ago