Implemented Selection.set_font() for Android

android/src/toga_android/widgets/selection.py

@@ -3,7 +3,7 @@
 
 from android import R
 from android.view import View
-from android.widget import AdapterView, ArrayAdapter, Spinner
+from android.widget import AdapterView, ArrayAdapter, Spinner, SpinnerAdapter
 
 from .base import Widget
 
@@ -20,14 +20,93 @@ def onNothingSelected(self, parent):
         self.impl.on_change(None)
 
 
+class TogaArrayAdapter(dynamic_proxy(SpinnerAdapter)):
+    def __init__(self, impl):
+        super().__init__()
+        self.impl = impl
+        self._default_textsize = -1
+        self._default_typeface = None
+        self._textsize = -1
+        self._typeface = None
+        self.adapter = ArrayAdapter(
+            self.impl._native_activity, R.layout.simple_spinner_item
+        )
+        self.adapter.setDropDownViewResource(R.layout.simple_spinner_dropdown_item)
+
+    def apply_font(self, tv):
+        if self.impl._font_impl and tv:
+            self.impl._font_impl.apply(
+                tv,
+                self._default_textsize,
+                self._default_typeface,
+            )
+            self._textsize = tv.getTextSize()
+            self._typeface = tv.getTypeface()
+
+    def cache_textview_defaults(self, tv):
+        self._default_textsize = tv.getTextSize()
+        self._default_typeface = tv.getTypeface()
+
+    def getDropDownView(self, position, convertView, parent):
+        tv = self.adapter.getDropDownView(position, convertView, parent)
+        self.apply_font(tv)
+        return tv
+
+    def getView(self, position, convertView, parent):
+        tv = self.adapter.getView(position, convertView, parent)
+        if self._default_textsize == -1:
+            self.cache_textview_defaults(tv)
+        self.apply_font(tv)
+        return tv
+
+    def clear(self):
+        return self.adapter.clear()
+
+    def getAutofillOptions(self):
+        return self.adapter.getAutofillOptions()
+
+    def getCount(self):
+        return self.adapter.getCount()
+
+    def getItem(self, position):
+        return self.adapter.getItem(position)
+
+    def getItemId(self, position):
+        return self.adapter.getItemId(position)
+
+    def getItemViewType(self, position):
+        return self.adapter.getItemViewType(position)
+
+    def getViewTypeCount(self):
+        return self.adapter.getViewTypeCount()
+
+    def hasStableIds(self):
+        return self.adapter.hasStableIds()
+
+    def insert(self, object, index):
+        return self.adapter.insert(object, index)
+
+    def isEmpty(self):
+        return self.adapter.isEmpty()
+
+    def registerDataSetObserver(self, observer):
+        self.adapter.registerDataSetObserver(observer)
+
+    def remove(self, object):
+        self.adapter.remove(object)
+
+    def unregisterDataSetObserver(self, observer):
+        self.adapter.unregisterDataSetObserver(observer)
+
+
 class Selection(Widget):
     focusable = False
+    _font_impl = None
 
     def create(self):
         self.native = Spinner(self._native_activity, Spinner.MODE_DROPDOWN)
         self.native.setOnItemSelectedListener(TogaOnItemSelectedListener(impl=self))
-        self.adapter = ArrayAdapter(self._native_activity, R.layout.simple_spinner_item)
-        self.adapter.setDropDownViewResource(R.layout.simple_spinner_dropdown_item)
+        self.adapter = TogaArrayAdapter(impl=self)
         self.native.setAdapter(self.adapter)
         self.last_selection = None
 
@@ -87,3 +166,10 @@ def rehint(self):
         self.native.measure(View.MeasureSpec.UNSPECIFIED, View.MeasureSpec.UNSPECIFIED)
         self.interface.intrinsic.width = at_least(self.native.getMeasuredWidth())
         self.interface.intrinsic.height = self.native.getMeasuredHeight()
+
+    def set_font(self, font):
+        self._font_impl = font._impl
+        tv = self.native.getSelectedView()
+        if tv:
+            self.adapter.apply_font(tv)
+        self.interface.refresh()

android/tests_backend/widgets/selection.py

@@ -8,6 +8,7 @@
 class SelectionProbe(SimpleProbe):
     native_class = Spinner
     supports_justify = False
+    default_font_size = 16
 
     def assert_resizes_on_content_change(self):
         xfail("Selection doesn't resize on content changes on this backend")
@@ -22,11 +23,11 @@ def color(self):
 
     @property
     def typeface(self):
-        xfail("Can't change the font of Selection on this backend")
+        return self.impl.adapter._typeface
 
     @property
     def text_size(self):
-        xfail("Can't change the font of Selection on this backend")
+        return self.impl.adapter._textsize
 
     @property
     def background_color(self):

changes/2130.misc.rst

@@ -0,0 +1 @@
+The set_font() method has been implemented for Selection on Android

examples/selection/selection/app.py

@@ -1,5 +1,6 @@
 import toga
-from toga.constants import COLUMN, ROW
+from toga.constants import COLUMN, ITALIC, NORMAL, ROW
+from toga.fonts import SYSTEM_DEFAULT_FONT_SIZE
 from toga.style import Pack
 
 
@@ -18,6 +19,9 @@ def startup(self):
         # Main window of the application with title and size
         self.main_window = toga.MainWindow(title=self.name, size=(640, 400))
 
+        # set font toggle
+        self.big_font = False
+
         # set up common styles
         label_style = Pack(flex=1, padding_right=24)
         box_style = Pack(direction=ROW, padding=10)
@@ -29,6 +33,14 @@ def startup(self):
             accessor="name",
             items=self.DATA_OPTIONS,
         )
+        self.styled_selection = toga.Selection(
+            style=Pack(
+                width=200,
+                padding=24,
+                font_family="serif",
+            ),
+            items=["Curium", "Titanium", "Copernicium"],
+        )
 
         self.main_window.content = toga.Box(
             children=[
@@ -86,10 +98,7 @@ def startup(self):
                     style=box_style,
                     children=[
                         toga.Label("Use some style!", style=label_style),
-                        toga.Selection(
-                            style=Pack(width=200, padding=24),
-                            items=["Curium", "Titanium", "Copernicium"],
-                        ),
+                        self.styled_selection,
                     ],
                 ),
                 toga.Box(
@@ -110,6 +119,12 @@ def startup(self):
                         ),
                     ],
                 ),
+                toga.Box(
+                    style=box_style,
+                    children=[
+                        toga.Button("Change font", on_press=self.change_font),
+                    ],
+                ),
             ],
             style=Pack(direction=COLUMN, padding=24),
         )
@@ -137,6 +152,15 @@ def report_selection(self, widget):
             f"Source: {self.source_selection.value.name} has weight {self.source_selection.value.weight}"
         )
 
+    def change_font(self, widget):
+        self.big_font = not self.big_font
+        if self.big_font:
+            self.styled_selection.style.font_size = 20
+            self.styled_selection.style.font_style = ITALIC
+        else:
+            self.styled_selection.style.font_size = SYSTEM_DEFAULT_FONT_SIZE
+            self.styled_selection.style.font_style = NORMAL
+
 
 def main():
     # App name and namespace