MaterialProgressDrawable.java 文件源码

/**
 * Draw the progress spinner
 */
public void draw(Canvas c, Rect bounds) {
    final RectF arcBounds = mTempBounds;
    arcBounds.set(bounds);
    arcBounds.inset(mStrokeInset, mStrokeInset);

    final float startAngle = (mStartTrim + mRotation) * 360;
    final float endAngle = (mEndTrim + mRotation) * 360;
    float sweepAngle = endAngle - startAngle;

    if (sweepAngle != 0) {
        mPaint.setColor(mCurrentColor);
        c.drawArc(arcBounds, startAngle, sweepAngle, false, mPaint);
    }

    drawTriangle(c, startAngle, sweepAngle, bounds);

    if (mAlpha < 255) {
        mCirclePaint.setColor(mBackgroundColor);
        mCirclePaint.setAlpha(255 - mAlpha);
        c.drawCircle(bounds.exactCenterX(), bounds.exactCenterY(), bounds.width() / 2,
                mCirclePaint);
    }
}