How To Output A Slider Value In App Designer

Sliders — Material Component For Android

Sliders used to view and select a value or range from the given slider bar.They're mainly used for adjusting settings such as volume and brightness, etc.

Sliders can use icons on both ends of the bar to represent a numeric or relative scale. The range of values or the nature of the values, such as volume change, can be communicated with icons.

Sliders add into Material design in library version 1.2.0. So, you need to add 1.2.0 or higher version on material design.

Types of sliders

There are two types of sliders.

Continuous Slider
Discrete Slider

Also, We have a another slider called range slider.

Lets see about these sliders in detail.

Continuous Slider

Continuous sliders allow us to select any value between the given start and end value.

For example, valueFrom = "0.0" and valueTo="100.0" in this case, you can select any values between from and to values like 55.5, 62.0, etc.

defining the slider In the layout,

          <com.google.android.material.slider.Slider
            android:id="@+id/continuousSlider"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:valueFrom="0.0"
            android:valueTo="100.0"
            android:value="20.0"/>

in the layout,

valueFrom : starting value of the slider.

valueTo : ending value of the slider.

value: setting the initial value of the slider.

Similarly, we can add a RangeSlider in a layout:

          <com.google.android.material.slider.RangeSlider
            android:id="@+id/rangeSlider"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:valueFrom="0.0"
            android:valueTo="100.0"
            android:stepSize="10.0"
            app:values="@array/initial_range_slider_values" />

The RangeSlider has app:values attribute to set the range for the slider. we need to provide the range in arrays.

values/arrays.xml:

          <resources>
            <array name="initial_range_slider_values">
            <item>20.0</item>
            <item>80.0</item>
            </array>
</resources>

Continous Range Slider — Continuous range slider

Values changes Listeners

We can observe the changes of the slider in two different ways.

addOnSliderTouchListener

by using addOnSliderTouchListener, we can observe the sliders start and stop touch position values.

          continuousSlider.addOnSliderTouchListener(object : Slider.OnSliderTouchListener {
            override fun onStartTrackingTouch(slider: Slider) {
            // Responds to when slider's touch event is being started
            Log.d("onStartTrackingTouch", slider.value.toString())
            }              override fun onStopTrackingTouch(slider: Slider) {
              // Responds to when slider's touch event is being stopped
              Log.d("onStopTrackingTouch", slider.value.toString())
              }
              })

similarly, we can add touch listener for the range slider.

          rangeSlider.addOnSliderTouchListener(object : RangeSlider.OnSliderTouchListener{
            override fun onStartTrackingTouch(slider: RangeSlider) {
            val values = rangeSlider.values
            Log.d("onStartTrackingTouch From", values[0].toString())
            Log.d("onStartTrackingTouch T0", values[1].toString())
            }              override fun onStopTrackingTouch(slider: RangeSlider) {
              val values = rangeSlider.values
              Log.d("onStopTrackingTouch From", values[0].toString())
              Log.d("onStopTrackingTouch T0", values[1].toString())
              }
              })

addOnChangeListener

Sliders OnChangeListener notified eveerytime the slider value changes.

          continuousSlider.addOnChangeListener(object: Slider.OnChangeListener{
            override fun onValueChange(slider: Slider, value: Float, fromUser: Boolean) {
            Log.d("addOnChangeListener", slider.value.toString())
            }
            })

Also, OnChangeListener for the RangeSlider.

          rangeSlider.addOnChangeListener(object : RangeSlider.OnChangeListener{              override fun onValueChange(slider: RangeSlider, value: Float, fromUser: Boolean) {
              val values = rangeSlider.values
              Log.d("From", values[0].toString())
              Log.d("T0", values[1].toString())
              }
              })

Discrete Slider

Discrete slider allows user to select an exact value in the given input range.

If you want to slider to be discrete, then you need to add attribute call android:stepSize="5.0". This will setup the step between valueFrom and valueTo values based on the stepSize value.

For example, valueFrom = 10.0, valueTo = 50.0 and stepSize = 10.0, then you can able to select values 10.0, 20.0, 30.0, 40.0, 50.0 only.

defining discrete slider in the layout:

          <com.google.android.material.slider.Slider
            android:id="@+id/discreteSlider"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:valueFrom="0.0"
            android:valueTo="100.0"
            android:stepSize="10.0"
            android:value="30.0"
            />

Also, we can add discrete in the RangeSlider.

We can observe the discrete slider values change same as continuous slider. Please check value changes Listeners above.

Setup the Slider Label

The label will be shown at the top of the slider thumb after you touch the thumb. Basically, Slider layout holding the current selected value of the slider.

We can change the behavior and label format using the below methods.

app:labelBehavior

You can change how it's drawn via the app:labelBehavior attribute or setLabelBehavior method.

app:labelBehavior having three different modes.

floating (default) — draw the label above the slider view.

withinBounds — draw the label within the slider view. So the label height will be include in the slider height.

gone — the label wont display.

LabelFormatter

By using a LabelFormatter you can change the display format of the selected values based on your requirement like 10KG, 12MB, like that.

That can be achieved through the setLabelFormatter method.That can be achieved through the setLabelFormatter method.

          continuousSlider.setLabelFormatter            {            value: Float            ->
              return@setLabelFormatter            "$${value.roundToInt()}"
}

In above code, I have rounded the selected values and converted into dollars.

key properties of sliders

A Slider has a four UI elements.

Track
Thumb
Value Label
Tick Mark (only for discrete slider)

Track Attributes

Thumb Attributes

Values Label Attributes

Tick Mark Attributes

Implementing slider theming

Sliders support Material Theming and can be customized in terms of color and typography.

Add all the theme related changes in res/values/styles.xml

Setting slider primary colors

          <style name="Widget.App.Slider" parent="Widget.MaterialComponents.Slider">
            <item name="materialThemeOverlay">@style/ThemeOverlay.App.Slider</item>
            <item name="labelStyle">@style/Widget.App.Tooltip</item>
            </style>              <style name="ThemeOverlay.App.Slider" parent="">
              <item name="colorPrimary">@color/green_200</item>
              <item name="colorOnPrimary">@color/green_900</item>
              <item name="colorOnSurface">@color/green_200</item>
              </style>

Theming slider Tooltip

          <style name="Widget.App.Tooltip" parent="Widget.MaterialComponents.Tooltip">
            <item name="android:textAppearance">@style/TextAppearance.App.Tooltip</item>
            <item name="backgroundTint">@color/green_200</item>
            </style>              <style name="TextAppearance.App.Tooltip" parent="TextAppearance.MaterialComponents.Tooltip">
              <item name="android:textColor">@android:color/black</item>
              </style>

Finally, add all the changes into AppTheme to reflect the changes in all the sliders.

          <style name="AppTheme" parent="Theme.MaterialComponents.Light.DarkActionBar">
            <item name="colorPrimary">@color/colorPrimary</item>
            <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
            <item name="colorAccent">@color/colorAccent</item>
            <item name="sliderStyle">@style/Widget.App.Slider</item>
            </style>

That's it.

You can download my Slider example in Github.

Thanks for the reading.

Please share if you like it.

Also, checkout my other post related to material design,

Android Chips : Material Component For Android

Android Snackbar Example