# Level Slider with Switch

Displays a vertically filled level for the last datastream value, and sets a new value when the user taps and drags the level control. The number of level segments displayed and selectable are adjustable by the widget settings. A switch below the vertical slider sets the assigned datastream to its minimum (OFF switch state) or maximum (ON switch state) when toggled.

### Datastream

* **LEVEL** - select or create a datastream of [data type](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/blynk.console/templates/datastreams/datastreams-common-settings/data-type) integer or double.
* **BUTTON** - select or create a datastream of [data type](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/blynk.console/templates/datastreams/datastreams-common-settings/data-type) integer or double.  The datastream may be the same as used for ‘LEVEL’, and if so then the switch will set the assigned datastream to the minimum value when OFF, and maximum value when ON.

### Widget Controls

The widget has the following controls:

* **Level Handle** - drag the level handle to adjust the level.
* **Switch** - tap to toggle the switch state. The associated datastream will be updated with its min (switch OFF) or max (switch ON) values.

### Widget Settings

* **NUMBER OF SEGMENTS** - defines visually how the levels are displayed relative to the latest datastream value, and the step behavior of the level handle when the number of segments is specified between 3 and 10. The ‘Fill’ option will use a continuous range between the min/max specified by ‘MIN/MAX VALUES’.
* **Unconnect bottom segment** - when enabled, the last bottom segment will always be displayed when the slider is at the minimum value.
* **Send on release** - when enabled, the selected value is sent when the user releases the control, otherwise it is continuously sent until released by the user (not recommended).

### How to process widget with the hardware

#### Reading the widget value

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

```cpp
BLYNK_WRITE(V1) {
// Called when the datastream V1 value changes

// Assign incoming value from pin V1 to a variable
// according to the datastream data type
int pinValue = param.asInt(); 
// double pinValue = param.asDouble();

if (pinValue == 0){
  // do something when the value is 0
} else if (pinValue > 0 && =< 128) {
  // do something when the value is between 1 and 128
} else {
  // print value to serial monitor
  Serial.print("V1 value is: "); 
  Serial.println(pinValue);
}

}
```

#### Changing the datastream value(s)

You can set the state of the widget by updating the assigned datastream value using the hardware or HTTP API. For a datastream V1 assigned data type of integer, double, or enum:

**Hardware:**

```cpp
Blynk.virtualWrite(V1, 1);
```

**HTTP API:**

```cpp
https://{server_address}/external/api/update/?token={your 32 char token}&V1=1
```

{% hint style="danger" %}
Don't put **`Blynk.virtualWrite()`**&#x69;nto 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](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/blynk-library-firmware-api/blynk-timer).
{% endhint %}

Sketch:[ Basic Sketch](https://github.com/blynkkk/blynk-library/blob/master/examples/GettingStarted/BlynkBlink/BlynkBlink.ino)

Sketch:[ ](https://github.com/blynkkk/blynk-library/blob/master/examples/More/Sync/ButtonInterrupt/ButtonInterrupt.ino)[Set Property](https://github.com/blynkkk/blynk-library/blob/master/examples/More/SetProperty/SetProperty_SingleValue/SetProperty_SingleValue.ino)

Sketch:[ ](https://github.com/blynkkk/blynk-library/blob/master/examples/More/Sync/ButtonPoll/ButtonPoll.ino)[VirtualPinWrite](https://github.com/blynkkk/blynk-library/blob/master/examples/GettingStarted/VirtualPinWrite/VirtualPinWrite.ino)

Sketch: [VirtualPinRead](https://github.com/blynkkk/blynk-library/blob/master/examples/GettingStarted/VirtualPinRead/VirtualPinRead.ino)

### Change Widget Properties

You can change certain properties of the Widget from your hardware. For that, use this command:&#x20;

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

Where:&#x20;

* `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

{% hint style="danger" %}
Don't put **`Blynk.setProperty()`**&#x69;nto 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.
{% endhint %}

### Properties you can change

You can change the properties *label*, *color*, *isDisabled*, *isHidden* of the widget from your hardware, or via an [HTTP API](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/blynk.cloud). 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.&#x20;

#### **Change Widget Label**

```cpp
Blynk.setProperty(V1, "label", "Air temperature");
```

#### **Set Widget Color**

Works only if the gradient was not set for this widget.

```cpp
//#D3435C - Blynk RED 
Blynk.setProperty(V1, "color", "#D3435C");
```

#### **Disable/Enable**

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

```cpp
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.

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

### Change widget properties via HTTPs API

## Updates the Datastream Property and all assigned Widgets

<mark style="color:blue;">`GET`</mark> `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&color=%23D3435C`

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

#### Path Parameters

| Name                                               | Type   | Description                                                                                                                                                                  |
| -------------------------------------------------- | ------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| {server address}<mark style="color:red;">\*</mark> | string | Get from the bottom right of your Blynk console. [More information](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/blynk.cloud/device-https-api/troubleshooting). |

#### Query Parameters

| Name                                    | Type   | Description                                                                                                                                                     |
| --------------------------------------- | ------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| token<mark style="color:red;">\*</mark> | string | Device [auth token](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/concepts/device#authtoken) from Device info                                       |
| pin<mark style="color:red;">\*</mark>   | string | The datastream [virtual pin](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/blynk.console/templates/datastreams/virtual-pin) (should start with "v") |
| {property}                              | string | The property of the widget you want to update: `label`, `color`, `isDisabled`, `isHidden`                                                                       |
| label                                   | string | the text used as widget label                                                                                                                                   |
| color                                   | string | button color hexadecimal, must include the hash # character urlencoded as %23. Works only if the gradient was not set for this widget.                          |
| isDisabled                              | string | true or false                                                                                                                                                   |
| isHidden                                | string | true or false                                                                                                                                                   |

{% tabs %}
{% tab title="200 Success" %}

```
```

{% endtab %}

{% tab title="400 Could not find a device token" %}

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

{% endtab %}
{% endtabs %}

### **Sync to the latest known state**&#x20;

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](https://docs.blynk.io/en/~/revisions/ynmC8lZ6FPocTYWigjcO/blynk-library-firmware-api/state-syncing) for more details.

```cpp
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()
}
```