Android实现炫酷SVG动画效果

svg是目前十分流行的图像文件格式了,svg严格来说应该是一种开放标准的矢量图形语言，使用svg格式我们可以直接用代码来描绘图像，可以用任何文字处理工具打开svg图像，通过改变部分代码来使图像具有交互功能，并可以随时插入到HTML中通过浏览器(如火狐浏览器)来观看。使用svg格式可让你设计激动人心的、高分辨率的Web图形页面。

svg格式具备目前网络流行的jpg和png等格式无法具备的优势：可以任意放大图形显示，但绝不会以牺牲图像质量为代价;可在svg图像中保留可编辑和可搜寻的状态;平均来讲，svg文件比其它格式的图像文件要小很多，因而下载也很快。

我们先来看几张Android上使用SVG的效果图：

                                        

从上面的图片看到，如果我们自己来实现这样的特效，非常的麻烦，不过接下来给大家介绍一个开源控件，就可以配合SVG实现这些效果。

首先我们来了解SVG文件的格式，举个例子：

 <svg xmlns="http://www.w3.org/2000/svg" id="svg" class="svg" viewBox="0 0 960 480" preserveAspectRatio="xMinYMin meet">
         <path fill="#B4BEC8" stroke="#B4BEC8" stroke-width="2px" stroke-miterlimit="10" d="M570.14 440.2l-29.165-28.99c-7.103-8.5-6.152-36.718-6.02-40.665H425.048c.133 3.947 1.082 32.164-6.018 40.666l-29.166 28.99c-1.237 1.404-1.712 2.505-1.623 3.37h-.054c.76 7.727 6.664 6.332 13.607 6.332H558.01c6.696 0 12.412 1.27 13.493-5.56.58-.953.274-2.282-1.364-4.14z" style="fill-opacity: 1; stroke-opacity: 0; -webkit-transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; stroke-dasharray: 474.095184326172px, 474.095184326172px; stroke-dashoffset: 0px;">path>

         <path fill="#C8D2DC" stroke="#C8D2DC" stroke-width="2px" stroke-miterlimit="10" d="M727.488 355.125c0 8.514-6.597 15.42-14.738 15.42h-465.5c-8.14 0-14.74-6.906-14.74-15.42V45.42c0-8.517 6.6-15.42 14.74-15.42h465.5c8.142 0 14.738 6.903 14.738 15.42v309.705z" style="fill-opacity: 1; stroke-opacity: 0; -webkit-transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; stroke-dasharray: 1645.18310546875px, 1645.18310546875px; stroke-dashoffset: 0px;">path>

         <path fill="#fff" stroke="#C8D2DC" stroke-width="2px" stroke-miterlimit="10" d="M489.01 343.713c-.042-4.223 3.447-6.254 3.605-6.352-1.963-2.866-5.018-3.263-6.102-3.31-2.602-.26-5.074 1.53-6.39 1.53s-3.356-1.49-5.506-1.448c-2.836.04-5.445 1.645-6.907 4.182-2.942 5.11-.75 12.672 2.116 16.814 1.4 2.02 3.072 4.305 5.268 4.22 2.114-.08 2.913-1.362 5.467-1.362 2.556 0 3.274 1.363 5.51 1.322 2.273-.04 3.716-2.064 5.105-4.098 1.61-2.35 2.273-4.63 2.313-4.748-.05-.02-4.434-1.7-4.48-6.75M484.807 331.31c1.168-1.41 1.953-3.37 1.738-5.327-1.68.068-3.713 1.12-4.916 2.53-1.08 1.247-2.027 3.245-1.77 5.16 1.87.143 3.784-.95 4.947-2.362" style="fill-opacity: 1; stroke-opacity: 0; -webkit-transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; stroke-dasharray: 115.244583129883px, 115.244583129883px; stroke-dashoffset: 0px;">path>

         <path fill="#3C4650" stroke="#3C4650" stroke-width="2px" stroke-miterlimit="10" d="M727.488 315.527V45.982c0-8.828-6.597-15.982-14.738-15.982h-465.5c-8.14 0-14.74 7.155-14.74 15.982v269.545H727.49z" style="fill-opacity: 1; stroke-opacity: 0; -webkit-transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; stroke-dasharray: 1547.85571289063px, 1547.85571289063px; stroke-dashoffset: 0px;">path>

         <path fill="#141E28" stroke="#141E28" stroke-width="2px" stroke-miterlimit="10" d="M251.2 48.887h457.205v245.52H251.2z" style="fill-opacity: 1; stroke-opacity: 0; -webkit-transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; transition: fill-opacity 1s ease-in-out, stroke-opacity 1s ease-in-out; stroke-dasharray: 1405.44995117188px, 1405.44995117188px; stroke-dashoffset: 0px;">path>
       svg>

上面的代码很复杂，如果说它们是代码的话，但是我们可以注意到，这种书写方式，有点类似于html，都是使用标签

使用最多的标签是path，也就是路径

有的人也会想到，要实现照片上的动态效果，我们可以使用Android自带的绘图类和函数，复杂的曲线路径，我们可以使用path这个类来制定

那会不会SVG里面的path，其实也是这样，那么我们就可以将SVG中的path，对应到android，然后绘制出来就好了。

SVG里面还有各种标签：

包括line直线，circle圆，rect矩形，eliipse椭圆，polygon多边形，等等

这些只要我们又一个SVG文件，都可以将其转换成java代码

作为一个程序员，我们当然不能手动去做这个工作，那就涉及两个问题，一个是SVG的解析，一个是解析后的绘制

幸运的是，已经有人完成了这个工作，并且在Github上开源 https://github.com/geftimov/android-pathview

这篇文章将作为一个简单的例子，来使用上面的开源控件

为了解析SVG,我们需要将一个androidsvg.jar包含进我们的lib

下面我们来看这个控件的简单使用，作为一个自定义控件，我们只需要在布局文件里面添加

 xml version="1.0" encoding="utf-8"?>
 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
     android:orientation="vertical"
     android:background="#ff0000"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent">

     <com.example.kaiyicky.myapplication.PathView
         xmlns:app="http://schemas.android.com/apk/res-auto"
         android:id="@+id/pathView"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         app:pathColor="@android:color/white"
         app:svg="@raw/ironman_white"
         app:pathWidth="5"/>
 LinearLayout>

其实app:svg指定了一个SVG文件，我们可以把这个文章放在raw目录下面

然后来看Activity里面：

 public class MainActivity extends FragmentActivity {

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_main);

         final PathView pathView = (PathView) findViewById(R.id.pathView);
 //        final Path path = makeConvexArrow(50, 100);
 //        pathView.setPath(path);
         pathView.setFillAfter(true);
         pathView.useNaturalColors();
         pathView.setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
                 pathView.getPathAnimator().
                         delay(100).
                         duration(1500).
                         interpolator(new AccelerateDecelerateInterpolator()).
                         start();
             }
         });
     }

     private Path makeConvexArrow(float length, float height) {
         final Path path = new Path();
         path.moveTo(0.0f, 0.0f);
         path.lineTo(length / 4f, 0.0f);
         path.lineTo(length, height / 2.0f);
         path.lineTo(length / 4f, height);
         path.lineTo(0.0f, height);
         path.lineTo(length * 3f / 4f, height / 2f);
         path.lineTo(0.0f, 0.0f);
         path.close();
         return path;
     }

 }

看到注释的部分，调用了makeConvexArraw()方法，如果我们没有在xml文件里面指定svg文件，我们也可以在代码中手动指定绘制的路径

让代码跑起来，点击屏幕，于是就实现了以下效果：

就是这么简单，至于这么制作SVG文件，大家可以找美工帮忙，使用ps和ai,可以将图片转换成SVG

最后是源码下载地址：http://download.csdn.net/detail/kangaroo835127729/9016349

整个过程有两个类，一个是SVG解析工具类：

 /**
  * Util class to init and get paths from svg.
  */
 public class SvgUtils {
     /**
      * It is for logging purposes.
      */
     private static final String LOG_TAG = "SVGUtils";
     /**
      * All the paths with their attributes from the svg.
      */
     private final List mPaths = new ArrayList();
     /**
      * The paint provided from the view.
      */
     private final Paint mSourcePaint;
     /**
      * The init svg.
      */
     private SVG mSvg;

     /**
      * Init the SVGUtils with a paint for coloring.
      *
      * @param sourcePaint - the paint for the coloring.
      */
     public SvgUtils(final Paint sourcePaint) {
         mSourcePaint = sourcePaint;
     }

     /**
      * Loading the svg from the resources.
      *
      * @param context     Context object to get the resources.
      * @param svgResource int resource id of the svg.
      */
     public void load(Context context, int svgResource) {
         if (mSvg != null) return;
         try {
             mSvg = SVG.getFromResource(context, svgResource);
             mSvg.setDocumentPreserveAspectRatio(PreserveAspectRatio.UNSCALED);
         } catch (SVGParseException e) {
             Log.e(LOG_TAG, "Could not load specified SVG resource", e);
         }
     }

     /**
      * Draw the svg to the canvas.
      *
      * @param canvas The canvas to be drawn.
      * @param width  The width of the canvas.
      * @param height The height of the canvas.
      */
     public void drawSvgAfter(final Canvas canvas, final int width, final int height) {
         final float strokeWidth = mSourcePaint.getStrokeWidth();
         rescaleCanvas(width, height, strokeWidth, canvas);
     }

     /**
      * Render the svg to canvas and catch all the paths while rendering.
      *
      * @param width  - the width to scale down the view to,
      * @param height - the height to scale down the view to,
      * @return All the paths from the svg.
      */
     public List getPathsForViewport(final int width, final int height) {
         final float strokeWidth = mSourcePaint.getStrokeWidth();
         Canvas canvas = new Canvas() {
             private final Matrix mMatrix = new Matrix();

             @Override
             public int getWidth() {
                 return width;
             }

             @Override
             public int getHeight() {
                 return height;
             }

             @Override
             public void drawPath(Path path, Paint paint) {
                 Path dst = new Path();

                 //noinspection deprecation
                 getMatrix(mMatrix);
                 path.transform(mMatrix, dst);
                 paint.setAntiAlias(true);
                 paint.setStyle(Paint.Style.STROKE);
                 paint.setStrokeWidth(strokeWidth);
                 mPaths.add(new SvgPath(dst, paint));
             }
         };

         rescaleCanvas(width, height, strokeWidth, canvas);

         return mPaths;
     }

     /**
      * Rescale the canvas with specific width and height.
      *
      * @param width       The width of the canvas.
      * @param height      The height of the canvas.
      * @param strokeWidth Width of the path to add to scaling.
      * @param canvas      The canvas to be drawn.
      */
     private void rescaleCanvas(int width, int height, float strokeWidth, Canvas canvas) {
         final RectF viewBox = mSvg.getDocumentViewBox();

         final float scale = Math.min(width
                         / (viewBox.width() + strokeWidth),
                 height / (viewBox.height() + strokeWidth));

         canvas.translate((width - viewBox.width() * scale) / 2.0f,
                 (height - viewBox.height() * scale) / 2.0f);
         canvas.scale(scale, scale);

         mSvg.renderToCanvas(canvas);
     }

     /**
      * Path with bounds for scalling , length and paint.
      */
     public static class SvgPath {
         /**
          * Region of the path.
          */
         private static final Region REGION = new Region();
         /**
          * This is done for clipping the bounds of the path.
          */
         private static final Region MAX_CLIP =
                 new Region(Integer.MIN_VALUE, Integer.MIN_VALUE,
                         Integer.MAX_VALUE, Integer.MAX_VALUE);
         /**
          * The path itself.
          */
         final Path path;
         /**
          * The paint to be drawn later.
          */
         final Paint paint;
         /**
          * The length of the path.
          */
         final float length;
         /**
          * The bounds of the path.
          */
         final Rect bounds;
         /**
          * The measure of the path, we can use it later to get segment of it.
          */
         final PathMeasure measure;

         /**
          * Constructor to add the path and the paint.
          *
          * @param path  The path that comes from the rendered svg.
          * @param paint The result paint.
          */
         SvgPath(Path path, Paint paint) {
             this.path = path;
             this.paint = paint;

             measure = new PathMeasure(path, false);
             this.length = measure.getLength();

             REGION.setPath(path, MAX_CLIP);
             bounds = REGION.getBounds();
         }
     }
 }

一个是SVG控件类：

 /**
  * PathView is an View that animate paths.
  */
 public class PathView extends View {
     /**
      * Logging tag.
      */
     public static final String LOG_TAG = "PathView";
     /**
      * The paint for the path.
      */
     private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
     /**
      * Utils to catch the paths from the svg.
      */
     private final SvgUtils svgUtils = new SvgUtils(paint);
     /**
      * All the paths provided to the view. Both from Path and Svg.
      */
     private List paths = new ArrayList(0);
     /**
      * This is a lock before the view is redrawn
      * or resided it must be synchronized with this object.
      */
     private final Object mSvgLock = new Object();
     /**
      * Thread for working with the object above.
      */
     private Thread mLoader;

     /**
      * The svg image from the raw directory.
      */
     private int svgResourceId;
     /**
      * Object that build the animation for the path.
      */
     private AnimatorBuilder animatorBuilder;
     /**
      * The progress of the drawing.
      */
     private float progress = 0f;

     /**
      * If the used colors are from the svg or from the set color.
      */
     private boolean naturalColors;
     /**
      * If the view is filled with its natural colors after path drawing.
      */
     private boolean fillAfter;
     /**
      * The width of the view.
      */
     private int width;
     /**
      * The height of the view.
      */
     private int height;

     /**
      * Default constructor.
      *
      * @param context The Context of the application.
      */
     public PathView(Context context) {
         this(context, null);
     }

     /**
      * Default constructor.
      *
      * @param context The Context of the application.
      * @param attrs   attributes provided from the resources.
      */
     public PathView(Context context, AttributeSet attrs) {
         this(context, attrs, 0);
     }

     /**
      * Default constructor.
      *
      * @param context  The Context of the application.
      * @param attrs    attributes provided from the resources.
      * @param defStyle Default style.
      */
     public PathView(Context context, AttributeSet attrs, int defStyle) {
         super(context, attrs, defStyle);
         paint.setStyle(Paint.Style.STROKE);
         getFromAttributes(context, attrs);
     }

     /**
      * Get all the fields from the attributes .
      *
      * @param context The Context of the application.
      * @param attrs   attributes provided from the resources.
      */
     private void getFromAttributes(Context context, AttributeSet attrs) {
         final TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.PathView);
         try {
             if (a != null) {
                 paint.setColor(a.getColor(R.styleable.PathView_pathColor, 0xff00ff00));
                 paint.setStrokeWidth(a.getFloat(R.styleable.PathView_pathWidth, 8.0f));
                 svgResourceId = a.getResourceId(R.styleable.PathView_svg, 0);
             }
         } finally {
             if (a != null) {
                 a.recycle();
             }
         }
     }

     /**
      * Set paths to be drawn and animated.
      *
      * @param paths - Paths that can be drawn.
      */
     public void setPaths(final List paths) {
         for (Path path : paths) {
             this.paths.add(new SvgUtils.SvgPath(path, paint));
         }
         synchronized (mSvgLock) {
             updatePathsPhaseLocked();
         }
     }

     /**
      * Set path to be drawn and animated.
      *
      * @param path - Paths that can be drawn.
      */
     public void setPath(final Path path) {
         paths.add(new SvgUtils.SvgPath(path, paint));
         synchronized (mSvgLock) {
             updatePathsPhaseLocked();
         }
     }

     /**
      * Animate this property. It is the percentage of the path that is drawn.
      * It must be [0,1].
      *
      * @param percentage float the percentage of the path.
      */
     public void setPercentage(float percentage) {
         if (percentage < 0.0f || percentage > 1.0f) {
             throw new IllegalArgumentException("setPercentage not between 0.0f and 1.0f");
         }
         progress = percentage;
         synchronized (mSvgLock) {
             updatePathsPhaseLocked();
         }
         invalidate();
     }

     /**
      * This refreshes the paths before draw and resize.
      */
     private void updatePathsPhaseLocked() {
         final int count = paths.size();
         for (int i = 0; i < count; i++) {
             SvgUtils.SvgPath svgPath = paths.get(i);
             svgPath.path.reset();
             svgPath.measure.getSegment(0.0f, svgPath.length * progress, svgPath.path, true);
             // Required only for Android 4.4 and earlier
             svgPath.path.rLineTo(0.0f, 0.0f);
         }
     }

     @Override
     protected void onDraw(Canvas canvas) {
         super.onDraw(canvas);

         synchronized (mSvgLock) {
             canvas.save();
             canvas.translate(getPaddingLeft(), getPaddingTop());
             final int count = paths.size();
             for (int i = 0; i < count; i++) {
                 final SvgUtils.SvgPath svgPath = paths.get(i);
                 final Path path = svgPath.path;
                 final Paint paint1 = naturalColors ? svgPath.paint : paint;
                 canvas.drawPath(path, paint1);
             }
             fillAfter(canvas);
             canvas.restore();
         }
     }

     /**
      * If there is svg , the user called setFillAfter(true) and the progress is finished.
      *
      * @param canvas Draw to this canvas.
      */
     private void fillAfter(final Canvas canvas) {
         if (svgResourceId != 0 && fillAfter && progress == 1f) {
             svgUtils.drawSvgAfter(canvas, width, height);
         }
     }

     @Override
     protected void onSizeChanged(final int w, final int h, int oldw, int oldh) {
         super.onSizeChanged(w, h, oldw, oldh);

         if (mLoader != null) {
             try {
                 mLoader.join();
             } catch (InterruptedException e) {
                 Log.e(LOG_TAG, "Unexpected error", e);
             }
         }
         if (svgResourceId != 0) {
             mLoader = new Thread(new Runnable() {
                 @Override
                 public void run() {

                     svgUtils.load(getContext(), svgResourceId);

                     synchronized (mSvgLock) {
                         width = w - getPaddingLeft() - getPaddingRight();
                         height = h - getPaddingTop() - getPaddingBottom();
                         paths = svgUtils.getPathsForViewport(width, height);
                         updatePathsPhaseLocked();
                     }
                 }
             }, "SVG Loader");
             mLoader.start();
         }
     }

     @Override
     protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
         super.onMeasure(widthMeasureSpec, heightMeasureSpec);
         if (svgResourceId != 0) {
             int widthSize = MeasureSpec.getSize(widthMeasureSpec);
             int heightSize = MeasureSpec.getSize(heightMeasureSpec);
             setMeasuredDimension(widthSize, heightSize);
             return;
         }

         int desiredWidth = 0;
         int desiredHeight = 0;
         final float strokeWidth = paint.getStrokeWidth() / 2;
         for (SvgUtils.SvgPath path : paths) {
             desiredWidth += path.bounds.left + path.bounds.width() + strokeWidth;
             desiredHeight += path.bounds.top + path.bounds.height() + strokeWidth;
         }
         int widthSize = MeasureSpec.getSize(widthMeasureSpec);
         int heightSize = MeasureSpec.getSize(heightMeasureSpec);
         int widthMode = MeasureSpec.getMode(widthMeasureSpec);
         int heightMode = MeasureSpec.getMode(widthMeasureSpec);

         int measuredWidth, measuredHeight;

         if (widthMode == MeasureSpec.AT_MOST) {
             measuredWidth = desiredWidth;
         } else {
             measuredWidth = widthSize;
         }

         if (heightMode == MeasureSpec.AT_MOST) {
             measuredHeight = desiredHeight;
         } else {
             measuredHeight = heightSize;
         }

         setMeasuredDimension(measuredWidth, measuredHeight);
     }

     /**
      * If the real svg need to be drawn after the path animation.
      *
      * @param fillAfter - boolean if the view needs to be filled after path animation.
      */
     public void setFillAfter(final boolean fillAfter) {
         this.fillAfter = fillAfter;
     }

     /**
      * If you want to use the colors from the svg.
      */
     public void useNaturalColors() {
         naturalColors = true;
     }

     /**
      * Animator for the paths of the view.
      *
      * @return The AnimatorBuilder to build the animation.
      */
     public AnimatorBuilder getPathAnimator() {
         if (animatorBuilder == null) {
             animatorBuilder = new AnimatorBuilder(this);
         }
         return animatorBuilder;
     }

     /**
      * Get the path color.
      *
      * @return The color of the paint.
      */
     public int getPathColor() {
         return paint.getColor();
     }

     /**
      * Set the path color.
      *
      * @param color -The color to set to the paint.
      */
     public void setPathColor(final int color) {
         paint.setColor(color);
     }

     /**
      * Get the path width.
      *
      * @return The width of the paint.
      */
     public float getPathWidth() {
         return paint.getStrokeWidth();
     }

     /**
      * Set the path width.
      *
      * @param width - The width of the path.
      */
     public void setPathWidth(final float width) {
         paint.setStrokeWidth(width);
     }

     /**
      * Get the svg resource id.
      *
      * @return The svg raw resource id.
      */
     public int getSvgResource() {
         return svgResourceId;
     }

     /**
      * Set the svg resource id.
      *
      * @param svgResource - The resource id of the raw svg.
      */
     public void setSvgResource(int svgResource) {
         svgResourceId = svgResource;
     }

     /**
      * Object for building the animation of the path of this view.
      */
     public static class AnimatorBuilder {
         /**
          * Duration of the animation.
          */
         private int duration = 350;
         /**
          * Interpolator for the time of the animation.
          */
         private Interpolator interpolator;
         /**
          * The delay before the animation.
          */
         private int delay = 0;
         /**
          * ObjectAnimator that constructs the animation.
          */
         private final ObjectAnimator anim;
         /**
          * Listener called before the animation.
          */
         private ListenerStart listenerStart;
         /**
          * Listener after the animation.
          */
         private ListenerEnd animationEnd;
         /**
          * Animation listener.
          */
         private PathViewAnimatorListener pathViewAnimatorListener;

         /**
          * Default constructor.
          *
          * @param pathView The view that must be animated.
          */
         public AnimatorBuilder(final PathView pathView) {
             anim = ObjectAnimator.ofFloat(pathView, "percentage", 0.0f, 1.0f);
         }

         /**
          * Set the duration of the animation.
          *
          * @param duration - The duration of the animation.
          * @return AnimatorBuilder.
          */
         public AnimatorBuilder duration(final int duration) {
             this.duration = duration;
             return this;
         }

         /**
          * Set the Interpolator.
          *
          * @param interpolator - Interpolator.
          * @return AnimatorBuilder.
          */
         public AnimatorBuilder interpolator(final Interpolator interpolator) {
             this.interpolator = interpolator;
             return this;
         }

         /**
          * The delay before the animation.
          *
          * @param delay - int the delay
          * @return AnimatorBuilder.
          */
         public AnimatorBuilder delay(final int delay) {
             this.delay = delay;
             return this;
         }

         /**
          * Set a listener before the start of the animation.
          *
          * @param listenerStart an interface called before the animation
          * @return AnimatorBuilder.
          */
         public AnimatorBuilder listenerStart(final ListenerStart listenerStart) {
             this.listenerStart = listenerStart;
             if (pathViewAnimatorListener == null) {
                 pathViewAnimatorListener = new PathViewAnimatorListener();
                 anim.addListener(pathViewAnimatorListener);
             }
             return this;
         }

         /**
          * Set a listener after of the animation.
          *
          * @param animationEnd an interface called after the animation
          * @return AnimatorBuilder.
          */
         public AnimatorBuilder listenerEnd(final ListenerEnd animationEnd) {
             this.animationEnd = animationEnd;
             if (pathViewAnimatorListener == null) {
                 pathViewAnimatorListener = new PathViewAnimatorListener();
                 anim.addListener(pathViewAnimatorListener);
             }
             return this;
         }

         /**
          * Starts the animation.
          */
         public void start() {
             anim.setDuration(duration);
             anim.setInterpolator(interpolator);
             anim.setStartDelay(delay);
             anim.start();
         }

         /**
          * Animation listener to be able to provide callbacks for the caller.
          */
         private class PathViewAnimatorListener implements Animator.AnimatorListener {

             @Override
             public void onAnimationStart(Animator animation) {
                 if (listenerStart != null) listenerStart.onAnimationStart();
             }

             @Override
             public void onAnimationEnd(Animator animation) {
                 if (animationEnd != null) animationEnd.onAnimationEnd();
             }

             @Override
             public void onAnimationCancel(Animator animation) {

             }

             @Override
             public void onAnimationRepeat(Animator animation) {

             }
         }

         /**
          * Called when the animation start.
          */
         public interface ListenerStart {
             /**
              * Called when the path animation start.
              */
             void onAnimationStart();
         }

         /**
          * Called when the animation end.
          */
         public interface ListenerEnd {
             /**
              * Called when the path animation end.
              */
             void onAnimationEnd();
         }
     }
 }