Android 自定义View - 饼图

    /**
     * 定义几种颜色
     */
    private static int COLOR[] = {Color.RED, Color.BLUE, Color.GREEN, Color.YELLOW, Color.BLACK};
    /**
     * 圆等分默认数目
     */
    private static int DIV_SIZE = 3;

    private Paint mPaint;
 　　/** 
　　　* 圆默认半径 
　　　*/
    private static final int DEFAULT_RADIUS = 200;
    private int mRadius = DEFAULT_RADIUS;

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

    public ColorCircle(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ColorCircle(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mPaint = new Paint();
        mPaint.setStyle(Paint.Style.FILL);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);

        int width;
        int height;

        if (widthMode == MeasureSpec.EXACTLY) {
            width = widthSize;
        } else {
            width = mRadius * 2 + getPaddingLeft() + getPaddingRight();
            if (widthMode == MeasureSpec.AT_MOST) {
                width = Math.min(width, widthSize);
            }
        }

        if (heightMode == MeasureSpec.EXACTLY) {
            height = heightSize;
        } else {
            height = mRadius * 2 + getPaddingTop() + getPaddingBottom();
            if (heightMode == MeasureSpec.AT_MOST) {
                height = Math.min(width, heightSize);
            }
        }

        setMeasuredDimension(width, height);
        mRadius = (int) (Math.min(width - getPaddingLeft() - getPaddingRight(),
                height - getPaddingTop() - getPaddingBottom()) * 1.0f / 2);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //平移Canvas到屏幕中心，之后的绘制以中心点为初始点
        canvas.translate((getWidth() + getPaddingLeft() - getPaddingRight()) / 2, 
　　　　　　　　　　　　　(getHeight() + getPaddingTop() - getPaddingBottom()) / 2);
        //定义一个RectF对象，表示扇形绘制区域
        RectF oval = new RectF(-mRadius, -mRadius, mRadius, mRadius);
        float firstAngle = 0.0f;
        float divideAngle = (360 * 1.0f) / DIV_SIZE;//根据DIV_SIZE来算每个扇形的角度
        for (int i=0; i<DIV_SIZE; i++) {
            mPaint.setColor(COLOR[i]);
            canvas.drawArc(oval, (firstAngle + i * divideAngle), divideAngle, true, mPaint);
        }
    }

    public void setDivSize(int size){
        DIV_SIZE = size;
        invalidate();
    }

    public int getDivSize(){
        DIV_SIZE = size;
    }

    mColorCircle = (ColorCircle)findViewById(R.id.color_circle);
    mSeekBar = (SeekBar)findViewById(R.id.seek_bar);
    mSeekBar.setMax(4);//因为颜色数目原因，这里seekBar的最大值设置为了4。
    int pro = mColorCircle.getSize();
    mSeekBar.setProgress(pro);

    mSeekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
        @Override
        public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
            mColorCircle.setDivSize(progress + 1);
        }

        @Override
        public void onStartTrackingTouch(SeekBar seekBar) {
        }

        @Override
        public void onStopTrackingTouch(SeekBar seekBar) {
        }
    });