Getting ready

In this recipe, we will use the Kv language for the design of the widgets, so, again, you will need to be familiar with the Kv language. Also, this recipe will use the common button and label widgets for reference. Obviously, to get more benefit, a device with an accelerometer is useful to run the code.

It is necessary to install a package for the use of the accelerometer in any mobile device; there is a way to deal with every specific device, but we do not have to reinvent the wheel. Let's use a Plyer package, which is an effort from many of the Kivy developers. To install the package from the shell, use:

$ sudo pip plyer install

Here where we are using pip to install the Plyer package, if you do not have pip installed in your computer, see the recipe Using Kivy Garden in Chapter 1, Kivy and the Kv language.

How to do it…

To complete this recipe, follow these steps:

How it works…

First, review the KV file. Note that the first line is the name of the rule, similar to the class in the Python file. Included in the next lines are the definitions of the four labels that we will use, so note the text of the label with the ID status. It will likely be blank, but it will be visible only when we modify this field from the Python code.

In the Python code, the first three lines are usual to import kivy and the widgets. The fourth line:

from kivy.clock import Clock

This will import the clock, which is used to get the accelerometer value in a time lap because, as we already said, this input is continuously providing data. The fifth line:

from plyer import accelerometer

This is importing the package plyer, which is the one that makes it possible to retrieve the data from an iOS or Android device. The sixth line:

class Accel(Widget):

This is the line where the class for the rule starts. Its name must be the same as the Kivy rule. The seventh, eighth, and ninth lines are:

 def __init__(self):
 super(Accel, self).__init__()
 self.sensorEnabled = False

These define the method that initializes the class and put in standby the accelerometer to be used later. The tenth, eleventh, twelfth, thirteenth, and fourteenth lines are:

 def get_acceleration(self, dt):
 val = accelerometer.acceleration
 self.ids.label1.text = "X: " + str(val[0])
 self.ids.label2.text = "Y: " + str(val[1])
 self.ids.label3.text = "Z: " + str(val[2])

These lines are used to retrieve the data of the accelerometer and will modify the text of the first three labels with the data of the acceleration. Now, look at the fifteenth line:

def pressed1(self):

This is where we define the method performed when the button is pressed. In the sixteenth line, we start a try sentence to start getting data from the accelerometer. In the seventeenth line, it is shown that if the accelerometer is disabled, enable it or vice versa. The eighteenth line is:

Clock.schedule_interval(self.get_acceleration, 1 / 20.)

In this line, we do the acquisition of the acceleration in time intervals. The acceleration is acquired by calling the get_acceleration method. The next class is usual to display our Kivy interface.

There's more…

Also, the plyer package allows you to interact with the compass and the GPS of the mobile device using a similar procedure. In the case of the compass, it is very easy to change. The change in the code is the word gyroscope for compass and acceleration for orientation.

See also

To get more details about widgets, see the recipes in Chapter 4, Widgets, and if you want to run the code in a mobile device, see Chapter 9, Kivy for Mobile Devices.