Android Tutorial Android shake event with PhoneSensors

Using the phone accelerometer it is possible to handle shake events.
The problem is of course to decide if the stream of values represents a shake.

The Shake code module finds shake patterns and raises a ShakeEvent when such occurs.

Using the Shake module is simple. Add Shake.bas code module to your project (Project - Add Existing module) and then you should add code similar to:

Code:

Sub Process_Globals
    Dim sensor As PhoneSensors
    Dim sounds As SoundPool
    Dim bounceId As Int
End Sub

Sub Globals

End Sub

Sub Activity_Create(FirstTime As Boolean)
    If FirstTime Then
        sensor.Initialize(sensor.TYPE_ACCELEROMETER)
        Shake.CallBackActivity = "Main" 'Set the activity that handles the Shake event
        sounds.Initialize(1)
        bounceId = sounds.Load(File.DirAssets, "break.mp3")
    End If
End Sub

Sub Activity_Resume
    sensor.StartListening("sensor")
End Sub

Sub Activity_Pause (UserClosed As Boolean)
    sensor.StopListening
End Sub

'Delegate the event handling to the Shake module
Sub sensor_SensorChanged (Values() As Float)
    Shake.HandleSensorEvent(Values)
End Sub

'This event is raised when a shake is detected
Sub ShakeEvent
    Activity.Color = Colors.RGB(Rnd(0, 255), Rnd(0, 255), Rnd(0, 255))
    sounds.Play(bounceId, 1, 1, 1, 0, 1)
End Sub

You should add a reference to the Phone library. This code also uses a SoundPool object to play a sound. So the Audio library is also required here.

Shake module also supports recording the sensors data to a CSV file.

This is useful for understanding the required pattern.
By recording the data and creating the following Excel graph:



I decided to use the change in the X acceleration (derivative line).

The attached program plays a sounds and changes the screen color when you shake the phone. It is not always easy to make a shake event. Playing a sound is a good cue for the user that the shake was "successful".

To prevent repetitive shake events, shakes are disabled for 1.5 seconds after a shake event.

 

See PhoneSensors.Initalize2:
http://www.basic4ppc.com/search?query=PhoneSensors.Initalize2

 

This is most probably an issue with the emulator. This code was first written with a Froyo device.

 

There are several parameters defined in the code module. You can change them from your UI.

 

You can see permissions in two places:
1. In the online help. For example: http://www.basic4ppc.com/android/help/phone.html#phoneid
2. After you compile your app you can press on the List Permissions button:



PhoneSensors does not add any permissions.

 

The same code will work from a service.