Why OnTouchEvent() override method of ViewRender is not firing? - xamarin

Question

Code:
This is my custom GridViewRenderer which contains scrollview control.
public class CustomGridViewRenderer : ViewRenderer<Grid, Android.Widget.GridView>
{
public override bool OnTouchEvent(global::Android.Views.MotionEvent events)
{
**//This event is not firing**
}
}
This is happening in xamarin.android

Answer 1

If you put the Scrollview in a custom GridView, when you touch this custom GridView, the ScrollView will get focus, so your OnTouchEvent cannot be executed.
We can set a padding for custom GridView as shown in the following code. For demonstrating the above conclusion, I set the custom GridView's background color to Green and ScrollView's backgroundColor to Red
<minitormediamanager:CustomGridView Margin="20,35,20,20" Padding="20" BackgroundColor="Green">
<ScrollView HeightRequest="50" BackgroundColor="Red">
<StackLayout>
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
<Label Text="By default, a Grid contains one row and one column." />
</StackLayout>
</ScrollView>
</minitormediamanager:CustomGridView>
Here is my Grid customRenderer code.
[assembly: ExportRenderer(typeof(MinitorMediaManager.CustomGridView), typeof(CustomGridViewRenderer))]
namespace MinitorMediaManager.Droid
{
// <Xamarin.Forms.Grid, Android.Views.View>
public class CustomGridViewRenderer : ViewRenderer<MinitorMediaManager.CustomGridView, Android.Views.View>
{
public CustomGridViewRenderer(Context context) : base(context)
{
}
public override bool OnTouchEvent(MotionEvent e)
{
Console.WriteLine("xxxxxxxxxxxxxxxxxxxxxxxxxx");
return base.OnTouchEvent(e);
}
}
}
You can see following running GIF. If I scroll or click the ScrollView(Red background), OnTouchEvent will not be executed, But If I click the GridView's padding(Green background), OnTouchEvent will be executed.
In the end, if you want to achieve a touch event, it can be done in the child controls, do not add the GirdView Or StackLayout(If you do not have padding)..