本项目来自：张奇
PercentageCircle 自定义圆环效果，指定中心园的背景颜色，圆环颜色，文字颜色，以及中心园的半径。
主要实现：
1.中间的圆 2.外边的圆环 3.中间的文字
//设置中心园的画笔
??????? mCirclePaint = new Paint();
??????? mCirclePaint.setAntiAlias(true);
??????? mCirclePaint.setColor(mCircleBackground);
??????? mCirclePaint.setStyle(Paint.Style.FILL);
??????? //设置文字的画笔
??????? mTextPaint = new Paint();
??????? mTextPaint.setColor(mTextColor);
??????? mTextPaint.setAntiAlias(true);
??????? mTextPaint.setStyle(Paint.Style.FILL);
??????? mTextPaint.setStrokeWidth((float) (0.025*mRadius));
??????? mTextPaint.setTextSize(mRadius/2);
??????? mTextPaint.setTextAlign(Align.CENTER);
??????? //设置外圆环的画笔
??????? mArcPaint = new Paint();
??????? mArcPaint.setAntiAlias(true);
??????? mArcPaint.setColor(mRingColor);
??????? mArcPaint.setStyle(Paint.Style.STROKE);
??????? mArcPaint.setStrokeWidth((float) (0.075*mRadius));

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