@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
super.onMeasure(widthMeasureSpec, heightMeasureSpec);
int widthSpectMode = MeasureSpec.getMode(widthMeasureSpec);
int widthSpectSize = MeasureSpec.getSize(widthMeasureSpec);
int heightSpectMode = MeasureSpec.getMode(heightMeasureSpec);
int heightSpectSize = MeasureSpec.getSize(heightMeasureSpec);
if (widthSpectMode == MeasureSpec.AT_MOST
&& heightSpectMode == MeasureSpec.AT_MOST) {
setMeasuredDimension(mWidth, mHeight);
} else if (widthSpectMode == MeasureSpec.AT_MOST) {
setMeasuredDimension(mWidth, heightSpectSize);
} else if (heightSpectMode == MeasureSpec.AT_MOST) {
setMeasuredDimension(widthSpectSize, mHeight);
}
}

private void init(Context context, AttributeSet attrs) {
drawFilter = new PaintFlagsDrawFilter(0, Paint.ANTI_ALIAS_FLAG
| Paint.FILTER_BITMAP_FLAG);
lineWidth = dip2px(context, lineWidth);
radius = dip2px(context, radius);
path = new Path();
pathCircle = new Path();
pathCircle2 = new Path();
//在path中添加一个顺时针的圆，这时候路径的起点和终点在最后边
//在画前半部分的脸和运动中的脸，起点在最右边比较方便的计算，但在最后那部分，运动的终点
//是在圆形的底部，这样把路径圆进行转换到底部，方便计算
pathCircle.addCircle(0, 0, radius, Direction.CW);
pathCircle2.addCircle(0, 0, radius, Direction.CW);
//利用Matrix，让pathCircle中的圆旋转90度，这样它的路径的起点和终点都在底部了
Matrix m = new Matrix();
m.postRotate(90);
pathCircle.transform(m);
//画脸的笔
paint = new Paint();
//画眼睛的笔
eyePaint = new Paint();
paint.setColor(blue);
eyePaint.setColor(blue);
paint.setStyle(Paint.Style.STROKE);
paint.setStrokeWidth(lineWidth);
eyePaint.setStrokeWidth(lineWidth);
//设置画脸的笔的端点为圆角(即起点和终点都是圆角)
paint.setStrokeCap(Paint.Cap.ROUND);
//使用PathMeasure计算路径的信息
pm = new PathMeasure();
pm.setPath(pathCircle, false);
pm2 = new PathMeasure();
pm2.setPath(pathCircle2, false);
//路径的长度，两个路径都是圆形，因此只计算其中一个即可
length = pm.getLength();
eyeRadius = (float)(lineWidth/2.0+lineWidth/5.0);
}

/**静态的笑脸
* @param canvas
*/
private void first(Canvas canvas) {
pm2.getSegment(10, length / 2-10, path, true);
canvas.drawPath(path, paint);
path = new Path();
drawEye(canvas);
}
/**一开始画的眼睛
* @param canvas
*/
public void drawEye(Canvas canvas) {
float x = (float) ((radius) * Math.cos(Math.PI * 45 / 180));
float y = x;
canvas.drawCircle(-x, -y, eyeRadius , eyePaint);
canvas.drawCircle(x, -y, eyeRadius , eyePaint);
}

/**从底部开始画一个在运动的圆，运动时间为0-3/4
* 即从270度开始，逆时针到0度
* @param canvas
*/
private void drawCircle(Canvas canvas) {
float degree = 270 - 270 * 4 / 3 * fraction;
float x = (float) ((radius ) * Math.cos(Math.PI * degree/180));
float y = -(float) ((radius ) * Math.sin(Math.PI * degree/ 180));
canvas.drawCircle(x, y, eyeRadius, eyePaint);
}

/* @param canvas
* @param pos 0代表画左眼，1代表画右眼
*/
public void drawOneEye(Canvas canvas, int pos) {
float x = (float) ((radius) * Math.cos(Math.PI * 45 / 180));
float y = x;
if (pos == 0) {
canvas.drawCircle(-x, -y, eyeRadius, eyePaint);
}else if(pos==1){
canvas.drawCircle(x, -y, eyeRadius , eyePaint);
}
}

public void drawFace(Canvas canvas){
//需要重新给path赋值
path=null;
path = new Path();
//根据时间来截取一定长度的路径，保存到path中，取值范围(0，length/2)
pm2.getSegment(0, (float) (length*(fraction-0.75)), path, true);
canvas.drawPath(path, paint);
}

public void rotateFace(Canvas canvas){
path=null;
path = new Path();
pm2.getSegment((float)(length*(fraction-5.0/4)), (float)(length*(fraction-5.0/4)+length*0.5), path, true);
canvas.drawPath(path, paint);
}

public void drawLastFact(Canvas canvas){
path = null;
path = new Path();
//从起点的1/4长度开始（即最左边的圆点)，到圆的路径的终点（即底部）
pm.getSegment((float)(1.0/4*length+3.0/2*(fraction-3.0/2)*length), (float)(length/2.0+length/8.0+(fraction-3.0/2)*length), path, true);
canvas.drawPath(path, paint);
}

public void performAnim() {
//上面计算的时间比例，加起来就是2，是运动了两周，因此这里设置为(0,2)
val = ValueAnimator.ofFloat(0, 2);
val.setDuration(duration);
val.addUpdateListener(new AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator arg0) {
fraction = (float) arg0.getAnimatedValue();
postInvalidate();
}
});
val.setRepeatCount(repeaCount);
val.start();
val.setRepeatMode(ValueAnimator.RESTART);
}

@Override
protected void onLayout(boolean changed, int left, int top, int right,
int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (changed) {
if (changed) {
mWidth = right - left;
mHeight = bottom - top;
}
}
}
@Override
protected void onDraw(Canvas canvas) {
//从画布上去除锯齿
canvas.setDrawFilter(drawFilter);
canvas.translate(mWidth / 2, mHeight / 2);
if (fraction == -1||!val.isRunning())
first(canvas);
//从底部开始画一个在运动的圆，运动时间为0-3/4
if (0 < fraction && fraction < 0.75) {
drawCircle(canvas);
}
//画左眼
if (fraction > 1.0 * 3 / 8&&fraction<1.0*6/4) {
drawOneEye(canvas,0);
}
//画右眼
if(fraction>1.0*5/8&&fraction<1.0*6/4){
drawOneEye(canvas, 1);
}
//画脸
if(fraction>=0.75&&fraction<=5.0/4){
drawFace(canvas);
}
//把脸运动起来
if(fraction>=5.0/4&&fraction<=(5.0/4+1.0/4)){
rotateFace(canvas);
}
if(fraction>=6.0/4){
drawLastFact(canvas);
}
}

/**
* 根据手机的分辨率从 dp 的单位 转成为 px(像素)
*/
public int dip2px(Context context, float dpValue) {
final float scale = context.getResources().getDisplayMetrics().density;
return (int) (dpValue * scale + 0.5f);
}
//字段
private final int blue = 0xff4aadff;
private int mWidth = 200;
private int mHeight = 200;
private int radius = 20;
private int lineWidth = 5;
private float eyeRadius;
Paint paint,eyePaint;
DrawFilter drawFilter;
Path path, pathCircle,pathCircle2;
PathMeasure pm,pm2;
float length;// 圆周长
float fraction = -1;
long duration = 2000;
int repeaCount = 8;
float x = 0, y = 0;
ValueAnimator val;

//在布局中的设置
<com.example.test22.view.SmileView 
android:id="@+id/smile"
android:layout_width="match_parent"
android:layout_height="100dp"/>

SmileView smile;
smile = (SmileView)findViewById(R.id.smile);
//设置动画执行时间，重复的次数。
smile.setDuration(2000);
smile.setRepeaCount(8);
//执行动画
smile.performAnim();
//停止动画
smile.cancelAnim();