From d1c9173c0e494067e997a781fa0ef6dc1abf1c4b Mon Sep 17 00:00:00 2001
From: Brady James Garvin <bgarvin@cse.unl.edu>
Date: Mon, 26 Jul 2021 21:28:44 -0500
Subject: [PATCH] Show how to makee data computed and stored in the main app
class available to a screen.
---
first_screen.kv | 3 +++
main.py | 12 +++++++++++-
second_screen.kv | 3 +++
second_screen.py | 6 +++++-
twoscreen.kv | 1 +
5 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/first_screen.kv b/first_screen.kv
index 08e2856..a1120fb 100644
--- a/first_screen.kv
+++ b/first_screen.kv
@@ -6,6 +6,9 @@
Button:
text: 'This button prints a number.'
on_press: root.print_number() # In a custom widget's Kv, `root` refers to the custom widget.
+ Button:
+ text: 'This button rolls a new number.'
+ on_press: app.reroll()
Button:
text: 'Change…'
on_press: app.open_second_screen() # But `app` still refers to the application object.
diff --git a/main.py b/main.py
index 2781354..6dbd102 100644
--- a/main.py
+++ b/main.py
@@ -1,5 +1,7 @@
+from random import randrange
+
from kivy.app import App
-from kivy.properties import BooleanProperty, StringProperty
+from kivy.properties import BooleanProperty, NumericProperty, StringProperty
# The following lines ensure that FirstScreen and SecondScreen are available for when the Kv code is loaded.
@@ -16,6 +18,8 @@ class TwoScreenApp(App):
advancing = BooleanProperty(True)
current_screen_name = StringProperty() # We must wait to select a screen until the app starts.
+ roll = NumericProperty(1)
+
def open_first_screen(self):
self.advancing = True
self.current_screen_name = 'first'
@@ -24,6 +28,12 @@ class TwoScreenApp(App):
self.advancing = False
self.current_screen_name = 'second'
+ def reroll(self):
+ new_roll = randrange(1, 6)
+ if new_roll >= self.roll:
+ new_roll +=1
+ self.roll = new_roll
+
def on_start(self):
self.open_first_screen() # Once the app starts, we can select the starting screen.
diff --git a/second_screen.kv b/second_screen.kv
index 7fcb6f5..9302369 100644
--- a/second_screen.kv
+++ b/second_screen.kv
@@ -5,6 +5,9 @@
text: 'This is the second screen.'
Label:
text: root.message # In a custom widget's Kv, `root` refers to the custom widget.
+ Button:
+ text: 'This button prints the roll from the first screen.'
+ on_press: root.print_roll()
Button:
text: 'Change…'
on_press: app.open_first_screen() # But `app` still refers to the application object.
diff --git a/second_screen.py b/second_screen.py
index 7521f71..50cb1b9 100644
--- a/second_screen.py
+++ b/second_screen.py
@@ -1,6 +1,6 @@
from kivy.lang import Builder
from kivy.uix.screenmanager import Screen
-from kivy.properties import StringProperty
+from kivy.properties import NumericProperty, StringProperty
Builder.load_file('second_screen.kv') # Because this is not the main app, we must load the Kv explicitly.
@@ -8,3 +8,7 @@ Builder.load_file('second_screen.kv') # Because this is not the main app, we mu
class SecondScreen(Screen):
message = StringProperty('Hello, World!') # This property is changed by twoscreen.kv.
+ roll = NumericProperty()
+
+ def print_roll(self):
+ print(f'The latest roll was a {self.roll}.')
diff --git a/twoscreen.kv b/twoscreen.kv
index 331e111..53ca161 100644
--- a/twoscreen.kv
+++ b/twoscreen.kv
@@ -11,3 +11,4 @@ ScreenManager:
SecondScreen:
name: 'second'
message: 'This is a message!' # The app sends information to the custom widgets by setting their properties.
+ roll: app.roll
--
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