When it comes to haptic feedback on mobile devices, less is more. Too much vibration can be annoying and even numbing to the hands, as the device is usually in-hand with the user's full attention. It can also be distracting from the user's intended task, which may lead the user to quickly turn off all haptics. However, well crafted haptics provide valuable sensory feedback that provide users with a richer engagement with their device.
This page explains use cases for using haptics, introduces classifications for haptic effects, and also covers basic guidelines for apps.
Use cases for adding haptics to your app
Here are some reasons for incorporating haptics into your app.
To notify the user of an event that needs their attention. Examples include an incoming phone call or text message, or an upcoming meeting on the calendar.
To confirm a state change in the device following a user action. Examples include click feedback for a button press, unlocking a phone, fingerprint acceptance or rejection, or activating the camera.
To delight the user with effects. Such effects could enhance an ongoing user action or emulate physical interaction. Examples include scroll feedback, a slider snapping into place, or haptic effects in sync with animations, sounds, videos, and games.
Haptics classifications
The haptic principles presented here are designed around clear haptics, rich haptics, and buzzy haptics.
Clear haptics
Clear haptics refers to crisp and clean sensations associated with a discrete event, such as button presses. These effects often aim to imitate a corresponding real-world mechanical action, like those felt when pressing on a physical button.
Android has predefined clear haptic effects in VibrationEffect. However,
in general apps should use action-oriented constants from
HapticFeedbackConstants to ensure consistency of effect and action across
the device.
The other advantage of action-oriented constants is that the platform can provide fallback behavior if a more complex effect isn't supported by the user's device.
As you expand the use cases of haptic feedback, the available clear haptics can sometimes feel plain and monotone. In that case, aim for rich haptics that are more expressive.
Rich haptics
Rich haptics generally require haptic actuators that have a wider frequency bandwidth, enabling greater expressiveness and range. Rich haptics can also be produced by sequencing clear haptics primitives in varied amplitudes and intervals.
Examples of rich haptic effects are:
- A "fluttery" sensation, similar to a butterfly flapping its wings on your fingertip
- The texture of a surface felt by a finger dragging or swiping across it
- The sensations of wobbliness and instability, or heaviness and reverberation
Buzzy haptics
Buzzy haptics can be characterized by noisy, sharp and penetrating vibrations that leave an after effect such as a tingling sensation even after the vibration is over. It also tends to have a ringing effect that feels like a reverberation before the vibration stops completely.
Examples of buzzy haptic sensations are:
- Operating a jackhammer
- Riding a motorcycle
- In mobile devices, a long-winded, ringing vibration after a key press
Dating back to pagers and feature phones, low-end mobile phones with low-performance haptic actuators or drivers tended to produce buzzy long vibrations for notification purposes.
Haptics design guidelines
At a high level, the design guidelines can be summarized as:
- Favor rich and clear haptics over buzzy haptics.
- Be consistent, both with the system and the app design.
- Be mindful of frequency of use, and importance.
Prioritize predefined haptic constants and effects
If your action is covered by a predefined action present in
HapticFeedbackConstants, use that constant. This ensures a consistent
user interaction experience, which is particularly valuable as an accessibility
consideration.
If you're creating your own effect, consider using the VibrationEffect
predefined effects and the VibrationEffect.Composition primitives. They
are more likely to give a consistent quality experience across devices that
support them.
Correlate event importance and frequency with strength
Haptic effects shouldn't overwhelm the user or feel gratuitous.
Haptic effects applied to very frequent events, like scrolling or moving a text handle, should be very subtle to provide a pleasant overall experience.
More important events, like refreshing a page or submitting a form, should be stronger than changing a toggle or scrolling on a list, for example.
Combine both concepts to create effects that become stronger as the interaction reaches a target, for example gradually increasing the amplitude of a sequence of ticks with dragging, dropping or snapping actions.
Be consistent
Be consistent within your app with the application of haptics. If a particular interaction, like form submission or in-app navigation, has haptic feedback, make sure the same effect is applied to all similar interactions. This helps users to associate a meaning to a particular haptic feedback.
Also be consistent with the Android system by using the same
HapticFeedbackConstants for well defined interactions, like time pickers or
virtual keyboards.
Design visual and audio experience together with haptics
Consider haptics as part of the total user experience.
We strongly recommend co-design of visual, audio, and haptic effects. Make it harmonious or congruent with visual animations and sound patterns. Visual and auditory inputs can enhance the haptics perceived, and a well-designed haptic effect can provide a sense of physicality to visual and audio effects.
Conversely, a haptic feedback that is played out of sync or that feels inconsistent with visual and audio effects can be a bit unsettling to the user. In some cases, the user may perceive the haptic actuator to be broken.
Avoid legacy one-shot vibrations for haptic feedback
Avoid using the legacy one-shot
vibrations, like the
ones defined by VibrationEffect.createOneShot or performed with the APIs
Vibrator.vibrate(long) and Vibrator.vibrate(long[], int).
These vibrations might feel buzzy when they last for a long period after the input waveform has ended, especially on devices with a low-performance haptic actuator or driver.
A good keyclick haptic feedback signal should last between 10 to 20 milliseconds. However, the actuator may continue to ring for another 20 to 50 milliseconds after a 20-millisecond input to the actuator has ended. Therefore, it's best to avoid single-shot vibrations for this type of feedback.