Android圆形进度音量条的实现

        先看下效果图：

概述：

1、首先自定义View的属性，画出圆环形状

自定义圆形音量条的流程：

private int mRoundColor = Color.parseColor("#ccffffff");//20%白色透明，圆环背景色
    private int mRroundProgressColor = Color.parseColor("#00b4ff");//蓝色，圆环进度颜色
    private float mRoundWidth = 25;//圆环宽度
    private int mMaxValue = 100;//最大值
    private int mCurrentPorgress;
    private int startAngle;

    public RoundProgressBar(Context context) {
        this(context, null);
    }

    public RoundProgressBar(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public RoundProgressBar(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        mPaint = new Paint();
        startAngle = -90;
        setLayerType(View.LAYER_TYPE_HARDWARE, null);
    }

2.画出最外圈圆环

mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeWidth(mRoundWidth);
        mPaint.setAntiAlias(true);
        canvas.drawCircle(center, center, radius, mPaint);

3.画出最里面圆环 

mPaint.setColor(mRroundProgressColor);
        RectF oval = new RectF(center - radius, center - radius, center
                + radius, center + radius);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStyle(Paint.Style.STROKE);
        canvas.drawArc(oval, startAngle, 360 * mCurrentPorgress / mMaxValue,
                false, mPaint);

4.设置圆环的进度显示

public synchronized void setProgress(int progress) {
        if (progress < 0) {
            return;
        }
        if (progress > mMaxValue) {
            progress = mMaxValue;
        }
        if (progress <= mMaxValue) {
            mCurrentPorgress = progress;
            postInvalidate();
        }
    }

至此，自定义圆环进度条就完成，代码很简单，最主要的是理解自定义绘制的原理。