background_color Transparency Fixes

android/src/toga_android/colors.py

@@ -1,7 +1,20 @@
+from android import R
 from android.graphics import Color
+from java import jint
+from org.beeware.android import MainActivity
 from travertino.colors import TRANSPARENT
 
-CACHE = {TRANSPARENT: Color.TRANSPARENT}
+from toga.colors import rgba
+
+typed_array = MainActivity.singletonThis.getTheme().obtainStyledAttributes(
+    [R.attr.colorBackground]
+)
+DEFAULT_BACKGROUND_COLOR = typed_array.getColor(0, 0)
+typed_array.recycle()
+
+CACHE = {
+    TRANSPARENT: Color.TRANSPARENT,
+}
 
 
 def native_color(c):
@@ -14,3 +27,17 @@ def native_color(c):
         CACHE[c] = color
 
     return color
+
+
+def toga_color(c):  # pragma: no cover
+    # Select the `int` overloads rather than the `long` ones.
+    color_int = jint(c)
+    if color_int == 0:
+        return TRANSPARENT
+    else:
+        return rgba(
+            Color.red(color_int),
+            Color.green(color_int),
+            Color.blue(color_int),
+            Color.alpha(color_int) / 255,
+        )

android/src/toga_android/container.py

@@ -1,6 +1,6 @@
 from android.widget import RelativeLayout
 
-from .widgets.base import Scalable
+from .widgets.base import ContainedWidget, Scalable
 
 
 class Container(Scalable):
@@ -51,13 +51,22 @@ def refreshed(self):
         self.native_content.setLayoutParams(lp)
 
     def add_content(self, widget):
-        self.native_content.addView(widget.native)
+        if isinstance(widget, ContainedWidget):
+            self.native_content.addView(widget.native_widget_container)
+        else:
+            self.native_content.addView(widget.native)
 
     def remove_content(self, widget):
-        self.native_content.removeView(widget.native)
+        if isinstance(widget, ContainedWidget):
+            self.native_content.removeView(widget.native_widget_container)
+        else:
+            self.native_content.removeView(widget.native)
 
     def set_content_bounds(self, widget, x, y, width, height):
         lp = RelativeLayout.LayoutParams(width, height)
         lp.topMargin = y
         lp.leftMargin = x
-        widget.native.setLayoutParams(lp)
+        if isinstance(widget, ContainedWidget):
+            widget.native_widget_container.setLayoutParams(lp)
+        else:
+            widget.native.setLayoutParams(lp)

android/src/toga_android/widgets/base.py

@@ -1,16 +1,19 @@
 from abc import ABC, abstractmethod
 from decimal import ROUND_HALF_EVEN, Decimal
 
-from android.graphics import PorterDuff, PorterDuffColorFilter, Rect
-from android.graphics.drawable import ColorDrawable, InsetDrawable
+from android.graphics import Color, PorterDuff, PorterDuffColorFilter
+from android.graphics.drawable import ColorDrawable
 from android.view import Gravity, View
 from android.widget import RelativeLayout
 from org.beeware.android import MainActivity
 from travertino.size import at_least
 
-from toga.constants import CENTER, JUSTIFY, LEFT, RIGHT, TRANSPARENT
-
-from ..colors import native_color
+from toga.constants import CENTER, JUSTIFY, LEFT, RIGHT
+from toga_android.colors import (
+    DEFAULT_BACKGROUND_COLOR,
+    native_color,
+    toga_color,
+)
 
 
 class Scalable:
@@ -134,31 +137,16 @@ def set_font(self, font):
     def set_background_color(self, color):
         pass
 
-    def set_background_simple(self, value):
-        if not hasattr(self, "_default_background"):
-            self._default_background = self.native.getBackground()
+    def set_background_simple(self, color):
+        self.native.setBackground(
+            ColorDrawable(Color.TRANSPARENT if color is None else native_color(color))
+        )
 
-        if value in (None, TRANSPARENT):
-            self.native.setBackground(self._default_background)
-        else:
-            background = ColorDrawable(native_color(value))
-            if isinstance(self._default_background, InsetDrawable):
-                outer_padding = Rect()
-                inner_padding = Rect()
-                self._default_background.getPadding(outer_padding)
-                self._default_background.getDrawable().getPadding(inner_padding)
-                insets = [
-                    getattr(outer_padding, name) - getattr(inner_padding, name)
-                    for name in ["left", "top", "right", "bottom"]
-                ]
-                background = InsetDrawable(background, *insets)
-            self.native.setBackground(background)
-
-    def set_background_filter(self, value):
+    def set_background_filter(self, color):
         self.native.getBackground().setColorFilter(
             None
-            if value in (None, TRANSPARENT)
-            else PorterDuffColorFilter(native_color(value), PorterDuff.Mode.SRC_IN)
+            if color is None
+            else PorterDuffColorFilter(native_color(color), PorterDuff.Mode.SRC_IN)
         )
 
     def set_alignment(self, alignment):
@@ -198,3 +186,85 @@ def align(value):
         CENTER: Gravity.CENTER_HORIZONTAL,
         JUSTIFY: Gravity.LEFT,
     }[value]
+
+
+# Most of the Android Widget have different effects applied them which provide
+# the native look and feel of Android. These widgets' background consists of
+# Drawables like ColorDrawable, InsetDrawable and other animation Effect Drawables
+# like RippleDrawable. Often when such Effect Drawables are used, they are stacked
+# along with other Drawables in a LayerDrawable.
+#
+# LayerDrawable once created cannot be modified and attempting to modify it or
+# creating a new LayerDrawable using the elements of the original LayerDrawable
+# stack, will destroy the native look and feel of the widgets. The original
+# LayerDrawable cannot also be properly cloned. Using `getConstantState()` on the
+# Drawable will produce an erroneous version of the original Drawable.
+#
+# These widgets are also affected by the background color of the parent inside which
+# they are present. Directly, setting background color also destroys the native look
+# and feel of these widgets. Moreover, these effects also serve the purpose of
+# providing visual aid for the action of these widgets.
+#
+# Hence, the best option to preserve the native look and feel of the these widgets is
+# to contain them in a `RelativeLayout` and set the background color to the layout
+# instead of the widget itself.
+#
+# ContainedWidget should act as a drop-in replacement against the Widget class for
+# such widgets, without requiring the widgets to do anything extra on their part.
+# It should be used for widgets that have an animated Effect Drawable as background
+# and their native look and feel needs to be preserved.
+class ContainedWidget(Widget):
+    def __init__(self, interface):
+
+        self._native_activity = MainActivity.singletonThis
+
+        self.interface = interface
+        self.interface._impl = self
+        self._container = None
+        self.native_widget_container = RelativeLayout(self._native_activity)
+        self.native = None
+        super().__init__(interface)
+
+        self.create()
+
+        self.native_widget_container.addView(self.native)
+
+        self.native.setLayoutParams(
+            RelativeLayout.LayoutParams(
+                RelativeLayout.LayoutParams.MATCH_PARENT,
+                RelativeLayout.LayoutParams.MATCH_PARENT,  # width  # height
+            )
+        )
+        # Immediately re-apply styles. Some widgets may defer style application until
+        # they have been added to a container.
+        self.interface.style.reapply()
+
+    def get_enabled(self):
+        return self.native.isEnabled() and self.native_widget_container.isEnabled()
+
+    def set_enabled(self, value):
+        self.native_widget_container.setEnabled(value)
+        self.native.setEnabled(value)
+
+    def focus(self):
+        if self.focusable:
+            self.native_widget_container.requestFocus()
+            self.native.requestFocus()
+
+    def set_hidden(self, hidden):
+        if hidden:  # pragma: no cover
+            self.native_widget_container.setVisibility(View.INVISIBLE)
+            self.native.setVisibility(View.INVISIBLE)
+        else:
+            self.native_widget_container.setVisibility(View.VISIBLE)
+            self.native.setVisibility(View.VISIBLE)
+
+    def set_background_simple(self, color):
+        self.native_widget_container.setBackground(ColorDrawable(native_color(color)))
+
+    # Widgets that need to set a different default background_color should
+    # override this method and set a background color for the None case.
+    def set_background_color(self, color):
+        self.set_background_simple(
+            toga_color(DEFAULT_BACKGROUND_COLOR) if color is None else color
+        )

android/src/toga_android/widgets/box.py

@@ -1,11 +1,13 @@
 from android.widget import RelativeLayout
 
+from toga.colors import TRANSPARENT
+
 from .base import Widget
 
 
 class Box(Widget):
     def create(self):
         self.native = RelativeLayout(self._native_activity)
 
-    def set_background_color(self, value):
-        self.set_background_simple(value)
+    def set_background_color(self, color):
+        self.set_background_simple(TRANSPARENT if color is None else color)

android/src/toga_android/widgets/button.py

@@ -5,6 +5,8 @@
 from java import dynamic_proxy
 from travertino.size import at_least
 
+from toga.colors import TRANSPARENT
+
 from .label import TextViewWidget
 
 
@@ -49,8 +51,8 @@ def set_icon(self, icon):
     def set_enabled(self, value):
         self.native.setEnabled(value)
 
-    def set_background_color(self, value):
-        self.set_background_filter(value)
+    def set_background_color(self, color):
+        self.set_background_filter(None if color is TRANSPARENT else color)
 
     def rehint(self):
         if self._icon:

android/src/toga_android/widgets/canvas.py

@@ -242,13 +242,12 @@ def get_image_data(self):
         )
         canvas = A_Canvas(bitmap)
         background = self.native.getBackground()
-        if background:
-            background.draw(canvas)
+        background.draw(canvas)
         self.native.draw(canvas)
 
         stream = ByteArrayOutputStream()
         bitmap.compress(Bitmap.CompressFormat.PNG, 0, stream)
         return bytes(stream.toByteArray())
 
-    def set_background_color(self, value):
-        self.set_background_simple(value)
+    def set_background_color(self, color):
+        self.set_background_simple(color)

android/src/toga_android/widgets/dateinput.py

@@ -4,6 +4,8 @@
 from android.app import DatePickerDialog
 from java import dynamic_proxy
 
+from toga_android.widgets.base import ContainedWidget
+
 from .internal.pickers import PickerBase
 
 
@@ -27,7 +29,7 @@ def onDateSet(self, view, year, month_0, day):
         self.impl.interface.value = date(year, month_0 + 1, day)
 
 
-class DateInput(PickerBase):
+class DateInput(PickerBase, ContainedWidget):
     @classmethod
     def _get_icon(cls):
         return R.drawable.ic_menu_my_calendar

android/src/toga_android/widgets/detailedlist.py

@@ -3,7 +3,7 @@
 from android import R
 from android.app import AlertDialog
 from android.content import DialogInterface
-from android.graphics import Rect
+from android.graphics import Color, Rect
 from android.view import Gravity, View
 from android.widget import ImageView, LinearLayout, RelativeLayout, ScrollView, TextView
 from java import dynamic_proxy
@@ -15,8 +15,7 @@
     # No cover due to not being able to test in CI
     SwipeRefreshLayout = None
 
-
-from .base import Widget
+from .base import ContainedWidget
 
 
 class DetailedListOnClickListener(dynamic_proxy(View.OnClickListener)):
@@ -96,7 +95,7 @@ def onRefresh(self):
             self._interface.on_refresh()
 
 
-class DetailedList(Widget):
+class DetailedList(ContainedWidget):
     def create(self):
         if SwipeRefreshLayout is None:  # pragma: no cover
             raise RuntimeError(
@@ -105,10 +104,9 @@ def create(self):
                 "is listed in your app's dependencies."
             )
         # get the selection color from the current theme
-        attrs = [R.attr.colorBackground, R.attr.colorControlHighlight]
+        attrs = [R.attr.colorControlHighlight]
         typed_array = self._native_activity.obtainStyledAttributes(attrs)
-        self.color_unselected = typed_array.getColor(0, 0)
-        self.color_selected = typed_array.getColor(1, 0)
+        self.color_selected = typed_array.getColor(0, 0)
         typed_array.recycle()
 
         self.native = self._refresh_layout = SwipeRefreshLayout(self._native_activity)
@@ -228,7 +226,7 @@ def clear(self):
 
     def _clear_selection(self):
         if self._selection is not None:
-            self._get_row(self._selection).setBackgroundColor(self.color_unselected)
+            self._get_row(self._selection).setBackgroundColor(Color.TRANSPARENT)
             self._selection = None
 
     def _set_selection(self, index):

android/src/toga_android/widgets/divider.py

@@ -3,20 +3,19 @@
 from android.widget import LinearLayout
 from travertino.size import at_least
 
+from toga_android.colors import toga_color
+
 from .base import Widget
 
 
 class Divider(Widget):
     def create(self):
         self.native = View(self._native_activity)
 
-        # Background color needs to be set or else divider will not be visible.
-        self.native.setBackgroundColor(Color.LTGRAY)
-
         self._direction = self.interface.HORIZONTAL
 
-    def set_background_color(self, value):
-        self.set_background_simple(value)
+    def set_background_color(self, color):
+        self.set_background_simple(toga_color(Color.LTGRAY) if color is None else color)
 
     def get_direction(self):
         return self._direction

android/src/toga_android/widgets/imageview.py

@@ -12,8 +12,8 @@ def create(self):
         self.native = A_ImageView(self._native_activity)
         self.native.setAdjustViewBounds(True)
 
-    def set_background_color(self, value):
-        self.set_background_simple(value)
+    def set_background_color(self, color):
+        self.set_background_simple(color)
 
     def set_image(self, image):
         if image: