android - 如何在 xamarin 中构建自定义 View

Question

是否有任何教程可以让我在 xamarin 中设计自定义 View ？我想使用 xamarin 为我的 android 应用程序构建缩放功能。

我尝试了以下代码，但它不起作用，我总是收到 android.view.InflateException: Binary XML file line #1: Error inflating class LA_Application.ZoomView 错误

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;
        }  
    }
}

在布局文件中

<?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 代码

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

    SetContentView(Resource.Layout.zoomview);

    /*some code*/
}

Answer 1

在布局文件中，您需要用小写字母写下您的类的路径。对我来说，Core.Droid.MyImageView 必须写成 core.droid.MyImageView。

我不确定是否只有第一个字母或所有字母必须小写，但您可以尝试 lA_Application.ZoomView 或 la_application.ZoomView。其中之一很可能会起作用:)