Merge pull request #1186 from paulproteus/detailed-list-allow-insert-row

Fix crash on adding new row to DetailedList

Author: freakboy3742

src/android/toga_android/widgets/base.py

@@ -1,18 +1,36 @@
 from ..libs.activity import MainActivity
 from ..libs.android_widgets import Gravity
 
+from rubicon.java.jni import java
+
 from toga.constants import CENTER, JUSTIFY, LEFT, RIGHT
 
 
+def _get_activity(_cache=[]):
+    """
+    Android Toga widgets need a reference to the current activity to pass it as `context` when creating
+    Android native widgets. This may be useful at any time, so we retain a global JNI ref.
+
+    :param _cache: List that is either empty or contains 1 item, the cached global JNI ref
+    """
+    if _cache:
+        return _cache[0]
+    # See MainActivity.onCreate() for initialization of .singletonThis:
+    # https://github.com/beeware/briefcase-android-gradle-template/blob/3.7/%7B%7B%20cookiecutter.formal_name%20%7D%7D/app/src/main/java/org/beeware/android/MainActivity.java
+    if MainActivity.singletonThis is None:
+        raise ValueError("Unable to find MainActivity.singletonThis from Python. This is typically set by "
+                         "org.beeware.android.MainActivity.onCreate().")
+    _cache.append(MainActivity(__jni__=java.NewGlobalRef(MainActivity.singletonThis)))
+    return _cache[0]
+
+
 class Widget:
     def __init__(self, interface):
         self.interface = interface
         self.interface._impl = self
         self._container = None
         self.native = None
-        # Capture a reference to the Java `MainActivity` instance, so that subclasses
-        # can pass it as `context` when creating native Android widgets.
-        self._native_activity = MainActivity.singletonThis
+        self._native_activity = _get_activity()
         self.create()
         # Immediately re-apply styles. Some widgets may defer style application until
         # they have been added to a container.

src/android/toga_android/widgets/detailedlist.py

@@ -33,9 +33,14 @@ class DetailedList(Widget):
     def create(self):
         # DetailedList is not a specific widget on Android, so we build it out
         # of a few pieces.
-        parent = android_widgets.LinearLayout(self._native_activity)
-        parent.setOrientation(android_widgets.LinearLayout.VERTICAL)
-        self.native = parent
+
+        if self.native is None:
+            self.native = android_widgets.LinearLayout(self._native_activity)
+            self.native.setOrientation(android_widgets.LinearLayout.VERTICAL)
+        else:
+            # If create() is called a second time, clear the widget and regenerate it.
+            self.native.removeAllViews()
+
         scroll_view = android_widgets.ScrollView(self._native_activity)
         scroll_view_layout_params = android_widgets.LinearLayout__LayoutParams(
                 android_widgets.LinearLayout__LayoutParams.MATCH_PARENT,
@@ -47,7 +52,7 @@ def create(self):
         self._android_swipe_refresh_layout = android_widgets.SwipeRefreshLayout(
             __jni__=java.NewGlobalRef(swipe_refresh_wrapper))
         swipe_refresh_wrapper.addView(scroll_view)
-        parent.addView(swipe_refresh_wrapper, scroll_view_layout_params)
+        self.native.addView(swipe_refresh_wrapper, scroll_view_layout_params)
         dismissable_container = android_widgets.LinearLayout(self._native_activity)
         dismissable_container.setOrientation(android_widgets.LinearLayout.VERTICAL)
         dismissable_container_params = android_widgets.LinearLayout__LayoutParams(
@@ -70,9 +75,9 @@ def _make_row(self, container, i):
         # Add user-provided icon to layout.
         icon_image_view = android_widgets.ImageView(self._native_activity)
         icon = self.interface.data[i].icon
-        icon.bind(self.interface.factory)
-        bitmap = android_widgets.BitmapFactory.decodeFile(str(icon._impl.path))
-        if bitmap is not None:
+        if icon is not None:
+            icon.bind(self.interface.factory)
+            bitmap = android_widgets.BitmapFactory.decodeFile(str(icon._impl.path))
             icon_image_view.setImageBitmap(bitmap)
         icon_layout_params = android_widgets.RelativeLayout__LayoutParams(
             android_widgets.RelativeLayout__LayoutParams.WRAP_CONTENT,