How to construct custom views in xamarin

Question

Is there any tutorial which will enable me to design custom views in xamarin?I want to build pinch zoom functionality for my android app using xamarin.

I have tried following code,but its not working,I am always getting android.view.InflateException: Binary XML file line #1: Error inflating class LA_Application.ZoomView error

using System;    
using System.Collections.Generic;
using System.Linq;    
using System.Text;    
using Android.App;    
using Android.Content;    
using Android.OS;    
using Android.Runtime;    
using Android.Util;    
using Android.Views;    
using Android.Widget;    
using Android.Graphics;

namespace LA_Application    
{

    public class ZoomView : FrameLayout      
    {

        private ScaleGestureDetector mScaleDetector;    
        private static float mScaleFactor = 1.0f;   


        public ZoomView (Context context) : base (context)
        {
            Initialize ();    
        }

        public ZoomView (Context context, IAttributeSet attrs) : base (context,attrs)    
        {
            Initialize ();    
        }

        public ZoomView (Context context, IAttributeSet attrs, int defStyle) : base (context, attrs, defStyle)
        {
            Initialize ();
        }

        void Initialize ()
        {
            mScaleDetector = new ScaleGestureDetector(Context, new ScaleListener());
        }

        public override bool OnTouchEvent (MotionEvent e)
        {
            mScaleDetector.OnTouchEvent(e);

            return true;
        }

        protected override void OnDraw(Android.Graphics.Canvas canvas)
        {
            base.OnDraw(canvas);

            canvas.Save();    
            canvas.Scale(mScaleFactor, mScaleFactor);
            canvas.Restore();
        }
    }

    private class ScaleListener : ScaleGestureDetector.SimpleOnScaleGestureListener
    {
        public override bool OnScale(ScaleGestureDetector detector)
        {
            mScaleFactor *= detector.ScaleFactor;

            // Don't let the object get too small or too large.
            mScaleFactor = Math.Max(0.1f, Math.Min(mScaleFactor, 5.0f));

            return true;
        }  
    }
}

}

and in layout file

<?xml version="1.0" encoding="utf-8"?>
<LA_Application.ZoomView xmlns:android="http://schemas.android.com/apk/res/android"
                         android:layout_width="match_parent"
                         android:layout_height="match_parent"
                         android:id="@+id/my_view" />

activity code

protected override void OnCreate (Bundle bundle)
{
    base.OnCreate (bundle);

    SetContentView(Resource.Layout.zoomview);

    /*some code*/
}

score 7 · Answer 1 · edited May 21 '17 at 00:35

7

In the layout file you need to write the path to your class in small letters. For me Core.Droid.MyImageView had to be written as core.droid.MyImageView.

I am not sure if only the first letter or all letter have to be written in small, but you can try either lA_Application.ZoomView or la_application.ZoomView. One of them will very likely work :)

edited May 21 '17 at 00:35

Quality Catalyst

6,531
8
38
62

answered Jul 22 '14 at 13:07

Jens

71
1
6

This fixed my issue. I was using the correct namespace in my project and it was working, but if the layout was in a sub library project, then I needed to use the lowercase version of the namespace ! – Stephane Mathis Aug 11 '14 at 08:49

score 2 · Answer 2 · edited May 23 '17 at 11:33

2

Here is the skeleton of how to create a custom view in xamarin.android

http://xandroid4net.blogspot.com/2014/09/custom-view.html

Then take Emmanuel Touzery answer and add it to the skeleton

android pinch zoom

edited May 23 '17 at 11:33

Community

1
1

answered Sep 06 '14 at 04:23

honeyws

151
1
3

score 1 · Accepted Answer · answered Jul 03 '13 at 11:27

1

I would suggest checking out this Java Android tutorial to get an idea of what you need to setup:

http://developer.android.com/training/custom-views/index.html

You may need to create an attributes xml file for your custom view.

Another approach you may want to consider is to use a fragment instead of a view:

http://docs.xamarin.com/guides/android/platform_features/fragments/fragments_walkthrough

answered Jul 03 '13 at 11:27

Ben Bishop

1,414
9
14

2

there is no xml file generated in Xamarin, only C# file - any ideas? – Arun Selva Kumar May 06 '15 at 13:06

SMagic · Answer 4 · 2021-11-08T14:36:46.683

I'v met with a similar problem today, and I accidentally find a way to solve it. Just add a "Register" before your defination of class ZoomView .

namespace LA_Application    
{
    [Register("la_application.ZoomView")]
    public class ZoomView : FrameLayout      
    {
        ...
    }
}

Right click FrameLayout in Visual Studio, and click "go to defination", then you'll find a "Register" before it. Visual Studio tells me that it is the android runtime attribute. I guess this is the real problem.

By the way, don't forget to write your namespace in lowercase. Hope to help you somehow.

How to construct custom views in xamarin

4 Answers4