WebView 判断放大缩小操作

时间：2021-10-30 04:11:36
using Android.App;

using Android.Widget;

using Android.OS;

using Android.Content;

using Android.Runtime;

using Android.Net;

using Microsoft.International.Converters.PinYinConverter;

using System;

using System.Text;

using Android.Webkit;

using Android.Views;

using System.Collections.Generic;

namespace android_filepiker_demo_test

{

    [Activity(Label = "android_filepiker_demo_test", MainLauncher = true, Icon = "@drawable/icon")]

    public class MainActivity : Activity

    {

        public class WebViewTouchParameter

        {

            public double Distance { get; set; }

            public int FontSize { get; set; }

            public int MinFontSize { get; set; }

            public int MaxFontSize { get; set; }

        }

        public delegate void FontSizeChanged(int fontSize);

        protected override void OnCreate(Bundle bundle)

        {

            base.OnCreate(bundle);

            SetContentView(Resource.Layout.Main);

            var button1 = FindViewById<Button>(Resource.Id.button1);

            button1.Click += Button1_Click;

            var web1 = FindViewById<WebView>(Resource.Id.web1);

            web1.Touch += Web1_Touch;

            web1.LoadData("<html><body style='font-size:12px;'><h1>abcde</h1></body></html>", "text/html", "utf-8");

        }

        private void Web1_Touch(object sender, Android.Views.View.TouchEventArgs e)

        {

            WebViewTouchHandler(e, new WebViewTouchParameter { MinFontSize = , MaxFontSize =  }, delegate(int fontSize)

            {

                var web1 = FindViewById<WebView>(Resource.Id.web1);

                web1.LoadDataWithBaseURL(null, "<html><body style='font-size:" + fontSize + "px;'><h1>" + fontSize + "px,abcde</h1></body></html>", "text/html", "utf-8", null);

            });

        }

private void Button1_Click(object sender, System.EventArgs e)

        {

        }

    }

}
private void WebViewTouchHandler(Android.Views.View.TouchEventArgs e, WebViewTouchParameter p, FontSizeChanged fsc)

        {

            var ev = e.Event;

            var action = ev.Action;

            switch (action)

            {

                case MotionEventActions.Pointer2Down:

                    {

                        System.Diagnostics.Debug.Print("Pointer2Down");

                        p.Distance = Math.Abs(Math.Sqrt(Math.Pow(ev.GetX() - ev.GetX(), )

                            + Math.Pow(ev.GetY() - ev.GetY(), )));

                        break;

                    }

                case MotionEventActions.Move:

                    {

                        if (e.Event.PointerCount == )

                        {

                            var distance = Math.Abs(Math.Sqrt(Math.Pow(ev.GetX() - ev.GetX(), )

                                    + Math.Pow(ev.GetY() - ev.GetY(), )));

                            p.FontSize += (int)((distance - p.Distance) / );

                            if (p.FontSize > p.MaxFontSize)

                                p.FontSize = p.MaxFontSize;

                            if (p.FontSize < p.MinFontSize)

                                p.FontSize = p.MinFontSize;

                            if (fsc != null && Math.Abs(distance - p.Distance) > )

                                fsc(p.FontSize);

                            p.Distance = distance;

                        }

                        break;

                    }

                case MotionEventActions.Up:

                    {

                        break;

                    }

                case MotionEventActions.Cancel:

                    {

                        break;

                    }

                case MotionEventActions.Pointer2Up:

                    {

                        break;

                    }

            }

        }

此代码经过测试，可以稳定实现放大缩小。代码衔接调用处参数可能需要调试，最新优化调试后，我只更新了最后一段核心代码段。

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