C# Canvas.Save方法代码示例

		/// <Docs>The Canvas to which the View is rendered.</Docs>
		/// <summary>
		/// Draw the specified canvas.
		/// </summary>
		/// <param name="canvas">Canvas.</param>
		public override void Draw (Canvas canvas)
		{			
			try
			{
				var element = Element as RoundCornerView;
				var cornerRadius = (float)element.CornerRadius*Resources.DisplayMetrics.Density;

				// Paint rounded rect itself
				canvas.Save();
				var paint = new Paint();
				paint.AntiAlias = true;
				var strokeWidth = (((float)element.BorderWidth)*Resources.DisplayMetrics.Density);
				paint.StrokeWidth = strokeWidth;

				if(element.BackgroundColor != Xamarin.Forms.Color.Transparent)
				{
					paint.SetStyle(Paint.Style.Fill);
					paint.Color = element.BackgroundColor.ToAndroid();
					canvas.DrawRoundRect(new RectF(0, 0, Width, Height), cornerRadius, cornerRadius, paint);
				}

				if(element.BorderColor != Xamarin.Forms.Color.Transparent)
				{
					paint.SetStyle(Paint.Style.Stroke);
					paint.Color = element.BorderColor.ToAndroid();
					canvas.DrawRoundRect(new RectF(0, 0, Width, Height), cornerRadius, cornerRadius, paint);
				}

				//Properly dispose
				paint.Dispose();
				canvas.Restore();

				// Create clip path
				var path = new Path();
				path.AddRoundRect(new RectF(0.0f + (strokeWidth/2), 0.0f + (strokeWidth/2), 
					Width - (strokeWidth/2), Height - (strokeWidth/2)), cornerRadius, cornerRadius, Path.Direction.Cw);
				
				canvas.Save();
				canvas.ClipPath(path);

				// Do base drawing
				for(var i=0; i<ChildCount; i++)
					GetChildAt(i).Draw(canvas);

				canvas.Restore();
				path.Dispose();
			}
			catch (Exception)
			{				
			}				
		}

		protected override void OnDraw(Canvas canvas) {
			base.OnDraw (canvas);
			if (mBlurredView != null) {
				if (prepare()) {
					// If the background of the blurred view is a color drawable, we use it to clear
					// the blurring canvas, which ensures that edges of the child views are blurred
					// as well; otherwise we clear the blurring canvas with a transparent color.
					if (mBlurredView.Background != null && mBlurredView.Background is ColorDrawable){
						mBitmapToBlur.EraseColor(((ColorDrawable) mBlurredView.Background).Color);
					}else {
						mBitmapToBlur.EraseColor(Color.Transparent);
					}

					mBlurredView.Draw(mBlurringCanvas);
					blur();

					canvas.Save();
					canvas.Translate(mBlurredView.GetX() - GetX(), mBlurredView.GetY() - GetY());
					canvas.Scale(mDownsampleFactor, mDownsampleFactor);
					canvas.DrawBitmap(mBlurredBitmap, 0, 0, null);
					canvas.Restore();
				}
				canvas.DrawColor(mOverlayColor);
			}
		}

 protected override bool DrawChild(Canvas canvas, global::Android.Views.View child, long drawingTime)
 {
     try
     {
         var radius = Math.Min(Width, Height) / 2;
         var strokeWidth = 10;
         radius -= strokeWidth / 2;
         //Create path to clip
         var path = new Path();
         path.AddCircle(Width / 2, Height / 2, radius, Path.Direction.Ccw);
         canvas.Save();
         canvas.ClipPath(path);
         var result = base.DrawChild(canvas, child, drawingTime);
         canvas.Restore();
         // Create path for circle border
         path = new Path();
         path.AddCircle(Width / 2, Height / 2, radius, Path.Direction.Ccw);
         var paint = new Paint();
         paint.AntiAlias = true;
         paint.StrokeWidth = 5;
         paint.SetStyle(Paint.Style.Stroke);
         paint.Color = global::Android.Graphics.Color.White;
         canvas.DrawPath(path, paint);
         //Properly dispose
         paint.Dispose();
         path.Dispose();
         return result;
     }
     catch (Exception ex)
     {
         Console.WriteLine("Unable to create circle image: " + ex);
     }
     return base.DrawChild(canvas, child, drawingTime);
 }

		private void drawPorcentajeOnCanvas(Canvas canvas)
		{
			base.OnDraw (canvas);

			canvas.Save ();

			canvas.DrawColor(Android.Graphics.Color.White);

			//Obtenemos el centro de nuesto canvas
			float x = this.MeasuredWidth / 2;
			float y = this.MeasuredHeight / 2;

			//Obtenemos el radio R1
			//Obtenemos el radio R2
			float R1 = 0;
			float R2 = 0;
			//if (canvas.Width < canvas.Height) {
			if (this.MeasuredWidth  < this.MeasuredHeight) {
				R1 = x;//Obtenemos el radio R1
				R2 = x-(x*por_rango/100);
			} else {
				R1 = y ;//Obtenemos el radio R1
				R2 = y-(y *por_rango/100);//Obtenemos el radio R2 que dejamos un 20% de margen

			}

			//Dibujamos el fondo de nuestro grafico que va ir creciendo de acuerdo al porcentaje descargado
			RectF rectF2 = new RectF(x-R1, y-R1,x+R1, y+R1);
			mPaintFondo.Color= Android.Graphics.Color.Rgb(19,184,213);

			int grados = 0;
			grados = 360 * porcentaje / 100;
			canvas.DrawArc(rectF2, 270, grados, true, mPaintFondo);

			//Fondo superior de nuestro texto
			mPaintSuperior.Color= Android.Graphics.Color.Rgb(50,58,69);
			canvas.DrawCircle(x,y , R2, mPaintSuperior);


			//Texto que nos indica el procentaje descargado
			mPaintTexto.SetTypeface (mFace);
			mPaintTexto.Color = Color.White;

			//Obtenemos el 30 % de radio de nuestro circulo de fondo, el cual sera el tamaño de letra utilzar;
			float MYTEXTSIZE = R2 *30/100;
			// Get the screen's density scale
			float scale = Application.Context.Resources.DisplayMetrics.Density;
			//Convert the dps to pixels, based on density scale
			int textSizePx = (int) (MYTEXTSIZE * scale + 0.5f);
			mPaintTexto.TextSize = textSizePx;

			//Obtenemos la posicion para centrar adecuadamente nuesto texto
			int xPos = (this.MeasuredWidth  / 2);
			int yPos = (int) ((this.MeasuredHeight / 2) - ((mPaintTexto.Descent() + mPaintTexto.Ascent()) / 2)) ; 

			string Texto_Porcentaje =porcentaje.ToString();
			canvas.DrawText (Texto_Porcentaje+" %", xPos,yPos, mPaintTexto);

			canvas.Restore();
		}

        public void DrawStopwatch(Canvas canvas)
        {
            canvas.Save();
            canvas.Translate(Width / 2F, Height / 2F);
            
            var tickMarks = new Path();
            tickMarks.AddCircle(0, 0, 90, Path.Direction.Cw);

            var scale = Math.Min(Width, Height) / 2F / 120;
            canvas.Scale(scale, scale);

            var paint = new Paint
            {
                StrokeCap = Paint.Cap.Square,
                Color = new Color(240, 240, 240)
            };

            paint.SetStyle(Paint.Style.Stroke);
            paint.StrokeWidth = 3;
            paint.SetPathEffect(MinuteDashEffect);
            canvas.DrawPath(tickMarks, paint);

            paint.Color = new Color(240, 240, 240);
            paint.StrokeWidth = 4;
            paint.SetPathEffect(FifthMinuteDashEffect);
            canvas.DrawPath(tickMarks, paint);
        }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="canvas"></param>
        /// <param name="child"></param>
        /// <param name="drawingTime"></param>
        /// <returns></returns>
        protected override bool DrawChild(Canvas canvas, Android.Views.View child, long drawingTime)
        {
            try
            {
                
                var radius = Math.Min(Width, Height) / 2;
                var strokeWidth = ((CircleImage)Element).BorderThickness;
                radius -= strokeWidth / 2;


               

                var path = new Path();
                path.AddCircle(Width / 2, Height / 2, radius, Path.Direction.Ccw);

                
                canvas.Save();
                canvas.ClipPath(path);

               

                var paint = new Paint();
                paint.AntiAlias = true;
                paint.SetStyle(Paint.Style.Fill);
                paint.Color = ((CircleImage)Element).FillColor.ToAndroid();
                canvas.DrawPath(path, paint);
                paint.Dispose();


                var result = base.DrawChild(canvas, child, drawingTime);

                canvas.Restore();

                path = new Path();
                path.AddCircle(Width / 2, Height / 2, radius, Path.Direction.Ccw);
                

                var thickness = ((CircleImage)Element).BorderThickness;
                if(thickness > 0.0f)
                {
                    paint = new Paint();
                    paint.AntiAlias = true;
                    paint.StrokeWidth = thickness;
                    paint.SetStyle(Paint.Style.Stroke);
                    paint.Color = ((CircleImage)Element).BorderColor.ToAndroid();
                    canvas.DrawPath(path, paint);
                    paint.Dispose();
                }
                
                path.Dispose();
                return result;
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine("Unable to create circle image: " + ex);
            }

            return base.DrawChild(canvas, child, drawingTime);
        }

 public void Draw(Canvas canvas)
 {
     canvas.Save();
     canvas.Translate((float)Position.X, (float)Position.Y);
     canvas.Rotate((float)Acceleration.Direction + ROTATION_OFFSET);
     mDrawable.Draw(canvas);
     canvas.Restore();
 }

        protected override bool DrawChild(Canvas canvas, View child, long drawingTime)
        {
            try
            {

                var radius = Math.Min(Width, Height) / 2;

                var borderThickness = (float)((CircleImage)Element).BorderThickness;

                int strokeWidth = 0;

                if (borderThickness > 0)
                {
                    var logicalDensity = Xamarin.Forms.Forms.Context.Resources.DisplayMetrics.Density;
                    strokeWidth = (int)Math.Ceiling(borderThickness * logicalDensity + .5f);
                }

                radius -= strokeWidth / 2;

                var path = new Path();
                path.AddCircle(Width / 2.0f, Height / 2.0f, radius, Path.Direction.Ccw);

                canvas.Save();
                canvas.ClipPath(path);

                var paint = new Paint();
                paint.AntiAlias = true;
                paint.SetStyle(Paint.Style.Fill);
                paint.Color = ((CircleImage)Element).FillColor.ToAndroid();
                canvas.DrawPath(path, paint);
                paint.Dispose();

                var result = base.DrawChild(canvas, child, drawingTime);

                canvas.Restore();

                path = new Path();
                path.AddCircle((float) Width / 2, (float) Height / 2, radius, Path.Direction.Ccw);

                if (strokeWidth > 0.0f)
                {
                    paint = new Paint {AntiAlias = true, StrokeWidth = strokeWidth};
                    paint.SetStyle(Paint.Style.Stroke);
                    paint.Color = ((CircleImage)Element).BorderColor.ToAndroid();
                    canvas.DrawPath(path, paint);
                    paint.Dispose();
                }

                path.Dispose();
                return result;
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine("Unable to create circle image: " + ex);
            }

            return base.DrawChild(canvas, child, drawingTime);
        }

		protected override void OnDraw (Canvas canvas)
		{
			base.OnDraw (canvas);
			canvas.Save ();
			canvas.Translate (_posX, _posY);
			canvas.Scale (_scaleFactor, _scaleFactor);
			_icon.Draw (canvas);
			canvas.Restore ();
		}

        // Rotate the canvas before drawing
        protected override void DispatchDraw(Canvas canvas)
        {
            canvas.Save (SaveFlags.Matrix);
            canvas.Rotate (-heading, Width * 0.5f, Height * 0.5f);

            base.DispatchDraw (canvas);

            canvas.Restore ();
        }

 private void ShowPath(Canvas canvas, int x, int y, Path.FillType ft, Paint paint)
 {
     canvas.Save();
     canvas.Translate(x, y);
     canvas.ClipRect(0, 0, 120, 120);
     canvas.DrawColor(Color.White);
     mPath.SetFillType(ft);
     canvas.DrawPath(mPath, paint);
     canvas.Restore();
 }

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

            canvas.Save();
            canvas.Scale(.4f, .5f, Width / 2, Height / 2);
            DrawCross(canvas);
            canvas.Restore();
        }

 protected override void OnDraw(Canvas canvas)
 {
     for (int i = 0; i < balls.Count; ++i)
     {
         ShapeHolder shapeHolder = balls[i];
         canvas.Save();
         canvas.Translate(shapeHolder.X, shapeHolder.Y);
         shapeHolder.Shape.Draw(canvas);
         canvas.Restore();
     }
 }

        protected override void OnDraw(Canvas canvas)
        {
            canvas.Save();
            if (RotationPivotPoint != null) {
                canvas.Rotate(RotationDegress, RotationPivotPoint.X, RotationPivotPoint.Y);
            } else {
                canvas.Rotate(RotationDegress);
            }

            base.OnDraw(canvas);
        }

        public override void Draw(Canvas canvas, ICharSequence text, int start, int end, float x, int top, int y, int bottom, Paint paint)
        {
            PrepView();

            canvas.Save();

            //Centering the token looks like a better strategy that aligning the bottom
            int padding = (bottom - top - View.Bottom) / 2;
            canvas.Translate(x, bottom - View.Bottom - padding);
            View.Draw(canvas);
            canvas.Restore();
        }