xamarin.android SurfaceView 实现 游戏 触摸摇杆

先上图

  

页面

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:gridSpec="1|8|#0093eeff|K:#ee8700ff:16,l:72,l:16,r|S:#0000ffff:16,0,l:16,56,l:16,0,r">

    <LinearLayout
        android:id="@+id/ll_controller"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="center"
        android:layout_weight="1"
        android:orientation="vertical"/>
</RelativeLayout>

代码

[Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : AppCompatActivity
    {
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.activity_main);

            LinearLayout relativeLayout = FindViewById<LinearLayout>(Resource.Id.ll_controller);
            RemoteSurfaceView remoteSurfaceView = new RemoteSurfaceView(this);
            var a = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.MatchParent, RelativeLayout.LayoutParams.MatchParent);
            remoteSurfaceView.LayoutParameters = a;
            relativeLayout.AddView(remoteSurfaceView);
        }
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
    }

    public class RemoteViewBg
    {
        private Bitmap bitmapBg;
        public RemoteViewBg(Bitmap bitmap)
        {
            bitmapBg = bitmap;
        }

        //背景的绘图函数
        public void draw(Canvas canvas, Paint paint, Rect src0, Rect dst0)
        {
            canvas.DrawBitmap(bitmapBg, src0, dst0, paint);
        }
    }

public class RemoteSurfaceView : SurfaceView, ISurfaceHolderCallback, IRunnable
    {
        // private float scale = this.Resources().getDisplayMetrics().density;
        private Thread th;
        private ISurfaceHolder sfh;
        private Canvas canvas;
        private Paint paint;
        private bool flag;

        private int bigCircleX = 0;
        private int bigCircleY = 0;
        private int bigCircleR = 0;
        //摇杆的X,Y坐标以及摇杆的半径
        private float smallCircleX = 0;
        private float smallCircleY = 0;
        private float smallCircleR = 0;


        private Bitmap bitmap;
        private RemoteViewBg remoteViewBg;
        public RemoteSurfaceView(Context context) : base(context)
        {
            sfh = this.Holder;
            sfh.AddCallback(this);
            paint = new Paint();
            paint.AntiAlias = true;
            Focusable = true;
            FocusableInTouchMode = true;
            SetZOrderOnTop(true);
            Holder.SetFormat(Format.Transparent);
        }
        public void SetLayoutParams() { }
        /***
         * 得到两点之间的弧度
         */
        public float getRad(float px1, float py1, float px2, float py2)
        {
            float x = px2 - px1;

            float y = py1 - py2;
            //斜边的长
            float z = (float)Java.Lang.Math.Sqrt(Java.Lang.Math.Pow(x, 2) + Java.Lang.Math.Pow(y, 2));
            float cosAngle = x / z;
            float rad = (float)Java.Lang.Math.Acos(cosAngle);

            if (py2 < py1)
            {
                rad = -rad;
            }
            return rad;
        }

        public void GetXY(float x, float y, float R, double rad)
        {

            smallCircleX = (float)(R * Java.Lang.Math.Cos(rad)) + x;

            smallCircleY = (float)(R * Java.Lang.Math.Sin(rad)) + y;
        }

        public void draw()
        {
            try
            {
                canvas = sfh.LockCanvas();
                canvas.DrawColor(Color.White);//Resources.GetColor(Resources.GetColor("colorAccent").));
                Rect src = new Rect(0, 0, bitmap.Width, bitmap.Height);
                Rect dst = new Rect(bigCircleX - bigCircleR, bigCircleY - bigCircleR, bigCircleX + bigCircleR, bigCircleY + bigCircleR);
                // 绘制图片
                remoteViewBg.draw(canvas, paint, src, dst);
                paint.Color = Color.AliceBlue;
                //绘制摇杆
                canvas.DrawCircle(smallCircleX, smallCircleY, smallCircleR, paint);
            }
            catch (Java.Lang.Exception e)
            {
                // TODO: handle exception
            }
            finally
            {
                try
                {
                    if (canvas != null)
                        sfh.UnlockCanvasAndPost(canvas);
                }
                catch (Java.Lang.Exception e2)
                {
                    e2.PrintStackTrace();
                }
            }
        }

        public void Run()
        {
            while (flag)
            {
                draw();
                try
                {
                    //Thread.Sleep(50);
                }
                catch (Java.Lang.Exception ex)
                {
                    ex.PrintStackTrace();
                }
            }
        }

        public void SurfaceCreated(ISurfaceHolder holder)
        {
            int width = Width;
            int height = Height;
            bigCircleX = width / 2;
            bigCircleY = height / 2;
            bigCircleR = width / 4;
            smallCircleX = width / 2;
            smallCircleY = height / 2;
            smallCircleR = width / 8;
            bitmap = BitmapFactory.DecodeResource(Resources, Resource.Mipmap.fangxiang);
            remoteViewBg = new RemoteViewBg(bitmap);
            th = new Thread(this);
            flag = true;
            th.Start();
        }
        public override bool OnTouchEvent(MotionEvent e)
        {
            if (e.Action == MotionEventActions.Down || e.Action == MotionEventActions.Move)
            {
                // 范围外触摸
                if (Java.Lang.Math.Sqrt(Java.Lang.Math.Pow((bigCircleX - (int)e.GetX()), 2) +
                    Java.Lang.Math.Pow((bigCircleY - (int)e.GetY()), 2)) >= bigCircleR)
                {

                    double tempRad = getRad(bigCircleX, bigCircleY, e.GetX(), e.GetY());

                    GetXY(bigCircleX, bigCircleY, bigCircleR, tempRad);
                }
                else
                {//范围内触摸
                    smallCircleX = (int)e.GetX();
                    smallCircleY = (int)e.GetY();
                }
            }
            else if (e.Action == MotionEventActions.Up)
            {
                smallCircleX = bigCircleX;
                smallCircleY = bigCircleY;

            }
            return true;
        }
        public void SurfaceDestroyed(ISurfaceHolder holder)
        {
            flag = false;
        }

        public void SurfaceChanged(ISurfaceHolder holder, [GeneratedEnum] Format format, int width, int height)
        {
          
        }
    }