properly colorize text preview gradient based on theme (day/night)

improve preview textview size/gradient position

Fixes #5232

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

src/main/java/com/owncloud/android/ui/adapter/OCFileListAdapter.java

@@ -335,15 +335,16 @@ public class OCFileListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHol
             PreviewTextFragment.setText(headerViewHolder.headerText, text, null, activity, true, true);
             headerViewHolder.headerView.setOnClickListener(v -> ocFileListFragmentInterface.onHeaderClicked());
 
-            Shader myShader = new LinearGradient(0,
-                                                 400,
-                                                 0,
-                                                 300,
-                                                 Color.WHITE,
-                                                 Color.BLACK,
-                                                 Shader.TileMode.CLAMP);
-
-            headerViewHolder.headerText.getPaint().setShader(myShader);
+            Shader shader = new LinearGradient(0,
+                                               headerViewHolder.headerText.getHeight()-20,
+                                               0,
+                                               headerViewHolder.headerText.getHeight() - 100,
+                                               activity.getResources().getColor(R.color.bg_default),
+                                               activity.getResources().getColor(R.color.text_color),
+                                               Shader.TileMode.CLAMP
+            );
+
+            headerViewHolder.headerText.getPaint().setShader(shader);
         } else {
             OCFileListGridImageViewHolder gridViewHolder = (OCFileListGridImageViewHolder) holder;
 

src/main/res/layout/list_header.xml

@@ -30,6 +30,9 @@
         android:id="@+id/headerText"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:padding="@dimen/standard_padding"
+        android:paddingTop="@dimen/standard_padding"
+        android:paddingLeft="@dimen/standard_padding"
+        android:paddingRight="@dimen/standard_padding"
+        android:paddingBottom="@dimen/zero"
         android:textColor="@color/text_color" />
 </LinearLayout>