- Kivy Cookbook
- Hugo Solis
- 574字
- 2021-07-16 20:39:57
Recognizing touch shapes
There is a useful tool provided by Kivy that permits us to recognize the shape of the touch that is performed. In this recipe, we will go through the foundations of using it.
Getting ready
In this recipe, we will use the Kv language for the design of the widgets, so we assume that the reader is familiar with the Kv language. Also, this recipe will use the common button and label widgets for reference.
How to do it…
Follow these steps:
- First, in the KV file, define a button and an empty label:
<MyW>: Button: id: button1 pos: 0,0 text: 'Hello' Label: id: label1 pos: 50, 200 text: '' - In the class of the widget in the Python code, we need to override the method
on_touch_move. - Change the button position to the information in
touch.pos. - Change the text in the label when a rectangular shape is present:
import kivy kivy.require('1.9.0') from kivy.app import App from kivy.uix.widget import Widget from kivy.input.shape import ShapeRect class MyW(Widget): def on_touch_move(self, touch): if 'pos' in touch.profile: self.ids.button1.pos = touch.pos if isinstance(touch.shape, ShapeRect): self.ids.label1.text =\ 'My touch have a rectangle shape of size' + str(touch.shape.width)+ str(touch.shape.height) class e6App(App): def build(self): return MyW() if __name__ == '__main__': e6App().run()
How it works…
In the KV file, the first line as usual is the name of the rule. The second line is the definition of the button widget, the third line is the ID of the button, which is necessary to do the call of the widget inside the Python code, the fourth line specifies the initial position of the button, and the fifth line is the definition of the text in the button. The sixth line is the definition of the label widget, the seventh line is ID of the label, the eighth line is the initial position of the label, and the ninth line is the initial text of the label.
In relation to the Python code, the initial four lines are the usual lines to use Kivy and the button widget. Next, the fifth one:
from kivy.input.shape import ShapeRect
In this line, we import the information of ShapeRect to be compared with the touch performed in the app. The sixth line is:
class MyW(Widget):
This is where we define the class associated with our rule in the KV file. The seventh line:
def on_touch_move(self, touch):
Here, we start the declaration of the dispatched on_touch_move method; you must note the parameter touch in the declaration, and this parameter is necessary to call the event by the input. The eighth and ninth lines are:
if 'pos' in touch.profile: self.ids.button1.pos = touch.pos
Those lines change the position of the button. The tenth line is:
if isinstance(touch.shape, ShapeRect):
It is where the comparison between the imported shape and the shape of the touch is performed. The eleventh line will change the label text with the dimension of the touch if this is rectangular. The last lines of the Python code are the usual lines to run and display our Kivy interface. Just remember that the initial part of the name of the class is:
class e6App(App):
It will be the same of the KV file; the name of the KV file in this case is e6.kv
See also
If you want to run your interface, take a look at our recipe Running your code, and to get more details about widgets, see the recipes in Chapter 4, Widgets.