Change Cursor on Android with Xamarin Forms Visual - xamarin.forms

Question

I have a Xamarin Forms Android application with the Material Design Visual. That seems to override the cursor color to black. Now I would like to create a dark theme. On IOS the cursor color changes with the font color to white. But on Android it stays black which makes it barely visible. Is there a way that I can override the color set as the cursor color?
Based on this Forum discussion I tried this Effect: https://forums.xamarin.com/discussion/42823/change-entry-cursor
protected override void OnAttached()
{
try
{
IntPtr IntPtrtextViewClass = JNIEnv.FindClass(typeof(TextView));
IntPtr mCursorDrawableResProperty = JNIEnv.GetFieldID(IntPtrtextViewClass, "mCursorDrawableRes", "I");
JNIEnv.SetField(Control.Handle, mCursorDrawableResProperty, Resource.Drawable.custom_cursor);
}
catch (Exception e) {
Console.WriteLine(e);
}
}
cursor drawable:
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
<solid android:color="#color/colorAccent"></solid>
<size android:width="2dp" />
</shape>
But with that the app crashes with the following error in the output:
JNI DETECTED ERROR IN APPLICATION: jfieldID int android.widget.TextView.mCursorDrawableRes not valid for an object of class md5a6256f8d5bc17d3565a450e514d4a6e7.MaterialFormsTextInputLayout

Answer 1

I ended up with a custom renderer for the entry.
[assembly: ExportRenderer(typeof(Entry), typeof(CustomEntryRenderer), new[] { typeof(VisualMarker.MaterialVisual) })]
namespace MoneyFox.Droid.Renderer
{
public class CustomEntryRenderer : MaterialEntryRenderer
{
public CustomEntryRenderer(Context context) : base(context) {
}
protected override void OnElementChanged(ElementChangedEventArgs<Entry> e) {
base.OnElementChanged(e);
// set cursor color
IntPtr IntPtrtextViewClass = JNIEnv.FindClass(typeof(TextView));
IntPtr mCursorDrawableResProperty = JNIEnv.GetFieldID(IntPtrtextViewClass, "mCursorDrawableRes", "I");
JNIEnv.SetField(Control.EditText.Handle, mCursorDrawableResProperty, Resource.Drawable.CustomCursor);
// try set cursor pointer color
try
{
TextView textViewTemplate = new TextView(Control.EditText.Context);
var field = textViewTemplate.Class.GetDeclaredField("mEditor");
field.Accessible = true;
var editor = field.Get(Control.EditText);
String[]
fieldsNames = { "mTextSelectHandleLeftRes", "mTextSelectHandleRightRes", "mTextSelectHandleRes" },
drawablesNames = { "mSelectHandleLeft", "mSelectHandleRight", "mSelectHandleCenter" };
for (Int32 index = 0; index < fieldsNames.Length && index < drawablesNames.Length; index++)
{
String
fieldName = fieldsNames[index],
drawableName = drawablesNames[index];
field = textViewTemplate.Class.GetDeclaredField(fieldName);
field.Accessible = true;
Int32 handle = field.GetInt(Control.EditText);
Drawable handleDrawable = Resources.GetDrawable(handle, null);
handleDrawable.SetColorFilter(Color.Accent.ToAndroid(), PorterDuff.Mode.SrcIn);
field = editor.Class.GetDeclaredField(drawableName);
field.Accessible = true;
field.Set(editor, handleDrawable);
}
}
catch (Exception ex)
{
LogManager.GetCurrentClassLogger().Error(ex);
}
}
}
}
There I was able to call Control.EditText.Handle, which accesses the native control. Unfortunately this is not accessible for effects.