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1. 每次都需要对填充的角度进行绘制

2. 每次都需要绘制外面的圆圈

   使用的函数：

drawArc(RectF oval, float startAngle, float sweepAngle, boolean useCenter, Paint paint)

Draw the specified arc, which will be scaled to fit inside the specified oval.

• RectF 就是范围了
• startAngle 开始角度，当你传入0的时候，相当于手表的三点钟方向
• sweepAngle扫描的角度
• useCenter 这个传入true，传入false感觉很奇怪，说不明白，可以自己试一下
• paint 画笔
  
  这里开始角度用270度 - 扫描的角度
  开始角度可以为负数

代码

public class MyView extends View {
       private Paint mOutPaint;    private Paint mInPaint;    private float currentValue;    public MyView(Context context) {        super(context);        init();    }    public MyView(Context context, @Nullable AttributeSet attrs) {        super(context, attrs);        init();    }    public MyView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        init();    }    private void init() {        mOutPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mOutPaint.setStrokeWidth(0);        mOutPaint.setStyle(Paint.Style.STROKE);        mOutPaint.setColor(Color.BLUE);        mInPaint = new Paint(Paint.ANTI_ALIAS_FLAG);        mInPaint.setColor(mOutPaint.getColor());    }    @Override    protected void onDraw(final Canvas canvas) {        int paddingLeft = getPaddingLeft();        int paddingTop = getPaddingTop();        int paddingRight = getPaddingRight();        int paddingBottom = getPaddingBottom();        final RectF drawRect = new RectF(paddingLeft, paddingTop, getWidth() - paddingRight, getHeight() - paddingBottom);        float end = (currentValue * 360);        float start = 270 - end;        canvas.drawArc(                drawRect,                start,                end,                true,                mInPaint);        canvas.drawOval(drawRect, mOutPaint);    }    public void doAnimation() {        ValueAnimator anim = ValueAnimator.ofFloat(1f, 0f);        anim.setDuration(3000);        anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {            @Override            public void onAnimationUpdate(ValueAnimator animation) {                currentValue = (float) animation.getAnimatedValue();                MyView.this.invalidate();            }        });        anim.start();    }}

下班了，溜了溜了！！！