Android background_color Transparency Fixes

android/src/toga_android/colors.py

@@ -1,7 +1,9 @@
 from android.graphics import Color
 from travertino.colors import TRANSPARENT
 
-CACHE = {TRANSPARENT: Color.TRANSPARENT}
+CACHE = {
+    TRANSPARENT: Color.TRANSPARENT,
+}
 
 
 def native_color(c):

android/src/toga_android/container.py

@@ -51,13 +51,13 @@ def refreshed(self):
         self.native_content.setLayoutParams(lp)
 
     def add_content(self, widget):
-        self.native_content.addView(widget.native)
+        self.native_content.addView(widget.native_toplevel)
 
     def remove_content(self, widget):
-        self.native_content.removeView(widget.native)
+        self.native_content.removeView(widget.native_toplevel)
 
     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)
+        widget.native_toplevel.setLayoutParams(lp)

android/src/toga_android/widgets/base.py

@@ -1,16 +1,15 @@
 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 native_color
 
 
 class Scalable:
@@ -54,6 +53,8 @@ def __init__(self, interface):
         self.init_scale(self._native_activity)
         self.create()
 
+        self.native_toplevel = self.native
+
         # Some widgets, e.g. TextView, may throw an exception if we call measure()
         # before setting LayoutParams.
         self.native.setLayoutParams(
@@ -63,6 +64,8 @@ def __init__(self, interface):
             )
         )
 
+        self._default_background_color = Color.TRANSPARENT
+
     @abstractmethod
     def create(self): ...
 
@@ -115,9 +118,9 @@ def set_bounds(self, x, y, width, height):
 
     def set_hidden(self, hidden):
         if hidden:
-            self.native.setVisibility(View.INVISIBLE)
+            self.native_toplevel.setVisibility(View.INVISIBLE)
         else:
-            self.native.setVisibility(View.VISIBLE)
+            self.native_toplevel.setVisibility(View.VISIBLE)
 
     def set_font(self, font):
         # By default, font can't be changed
@@ -128,33 +131,20 @@ def set_font(self, font):
     # appearance. So each widget must decide how to implement this method, possibly
     # using one of the utility functions below.
     def set_background_color(self, color):
-        pass
+        self.set_background_simple(color)
 
-    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_toplevel.setBackground(
+            ColorDrawable(
+                self._default_background_color 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_text_align(self, alignment):
@@ -194,3 +184,47 @@ def android_text_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 also draw some of their background effects on their native parent.
+# But in the Widget base class, the native parent is actually the root Box of the
+# layout, and the parent Box is stacked under its children without any native
+# parent/child relationship. So if the parent Box has a background color, it may
+# conceal some of the background elements of its children.
+#
+# 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):
+        super().__init__(interface)
+
+        self.native_toplevel = RelativeLayout(self._native_activity)
+        self.native_toplevel.addView(self.native)
+
+        self.native.setLayoutParams(
+            RelativeLayout.LayoutParams(
+                RelativeLayout.LayoutParams.MATCH_PARENT,
+                RelativeLayout.LayoutParams.MATCH_PARENT,
+            )
+        )
+        # Immediately re-apply styles. Some widgets may defer style application until
+        # they have been added to a container.
+        self.interface.style.reapply()

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

@@ -243,13 +243,12 @@ 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/divider.py

@@ -16,7 +16,8 @@ def create(self):
         self._direction = self.interface.HORIZONTAL
 
     def set_background_color(self, value):
-        self.set_background_simple(value)
+        # Do nothing, since background color of Divider shouldn't be changed.
+        pass
 
     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:

android/src/toga_android/widgets/label.py

@@ -7,6 +7,7 @@
 from android.widget import TextView
 from travertino.size import at_least
 
+from toga.colors import TRANSPARENT
 from toga.constants import JUSTIFY
 from toga_android.colors import native_color
 
@@ -29,12 +30,6 @@ def set_font(self, font):
             self.native, font._impl, self._default_typeface, self._default_text_size
         )
 
-    def set_background_color(self, value):
-        # In the case of EditText, this causes any custom color to hide the bottom
-        # border line, but it's better than set_background_filter, which affects *only*
-        # the bottom border line.
-        self.set_background_simple(value)
-
     def set_color(self, value):
         if value is None:
             self.native.setTextColor(self._default_text_color)
@@ -82,3 +77,6 @@ def rehint(self):
 
     def set_text_align(self, value):
         self.set_textview_alignment(value, Gravity.TOP)
+
+    def set_background_color(self, color):
+        self.set_background_simple(TRANSPARENT if color is None else color)

android/src/toga_android/widgets/scrollcontainer.py

@@ -100,5 +100,5 @@ def set_position(self, horizontal_position, vertical_position):
         self.hScrollView.setScrollX(self.scale_in(horizontal_position))
         self.vScrollView.setScrollY(self.scale_in(vertical_position))
 
-    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/selection.py

@@ -5,7 +5,7 @@
 from android.widget import AdapterView, ArrayAdapter, Spinner
 from java import dynamic_proxy
 
-from .base import Widget
+from toga_android.widgets.base import ContainedWidget
 
 
 class TogaOnItemSelectedListener(dynamic_proxy(AdapterView.OnItemSelectedListener)):
@@ -20,7 +20,7 @@ def onNothingSelected(self, parent):
         self.impl.on_change(None)
 
 
-class Selection(Widget):
+class Selection(ContainedWidget):
     focusable = False
 
     def create(self):

android/src/toga_android/widgets/slider.py

@@ -5,9 +5,9 @@
 from android.widget import SeekBar
 from java import dynamic_proxy
 
+from toga.colors import TRANSPARENT
 from toga.widgets.slider import IntSliderImpl
-
-from .base import Widget
+from toga_android.widgets.base import ContainedWidget
 
 # Implementation notes
 # ====================
@@ -31,7 +31,7 @@ def onStopTrackingTouch(self, native_seekbar):
         self.impl.interface.on_release()
 
 
-class Slider(Widget, IntSliderImpl):
+class Slider(ContainedWidget, IntSliderImpl):
     focusable = False
     TICK_DRAWABLE = None
 
@@ -71,3 +71,6 @@ def rehint(self):
         self.interface.intrinsic.height = self.scale_out(
             self.native.getMeasuredHeight(), ROUND_UP
         )
+
+    def set_background_color(self, color):
+        self.set_background_simple(TRANSPARENT if color is None else color)

android/src/toga_android/widgets/switch.py

@@ -5,6 +5,8 @@
 from java import dynamic_proxy
 from travertino.size import at_least
 
+from toga_android.widgets.base import ContainedWidget
+
 from .label import TextViewWidget
 
 
@@ -17,7 +19,7 @@ def onCheckedChanged(self, _button, _checked):
         self._impl.interface.on_change()
 
 
-class Switch(TextViewWidget):
+class Switch(TextViewWidget, ContainedWidget):
     focusable = False
 
     def create(self):

android/src/toga_android/widgets/table.py

@@ -212,8 +212,8 @@ def insert_column(self, index, heading, accessor):
     def remove_column(self, index):
         self.change_source(self.interface.data)
 
-    def set_background_color(self, value):
-        self.set_background_simple(value)
+    def set_background_color(self, color):
+        self.set_background_simple(color)
 
     def set_font(self, font):
         self._font_impl = font._impl

android/src/toga_android/widgets/textinput.py

@@ -6,6 +6,7 @@
 from java import dynamic_proxy
 
 from toga_android.keys import toga_key
+from toga_android.widgets.base import ContainedWidget
 
 from .label import TextViewWidget
 
@@ -55,7 +56,7 @@ def onFocusChange(self, view, has_focus):
             self.impl._on_lose_focus()
 
 
-class TextInput(TextViewWidget):
+class TextInput(ContainedWidget, TextViewWidget):
     def create(self, input_type=InputType.TYPE_CLASS_TEXT):
         self.native = EditText(self._native_activity)
         self.native.setInputType(input_type)