Android-->模仿360底部导航按钮

//首先绘制 内圆. 也就是没有透明颜色的圆
mPaint.setColor(mCircleColor);
canvas.drawCircle(mCx, mCy, Math.min(curRadius, mCircleRadius), mPaint);

//其次 绘制,带有透明颜色的圆
mPaint.setColor(mCircleColorOut);
canvas.drawCircle(mCx, mCy, Math.min(curRadius, mCircleRadiusOut), mPaint);

//最后判断是否是左右特殊位置, 绘制arc
if (drawLeft) {
mPaint.setColor(mCircleColor);
canvas.drawArc(getArcRecF(Math.min(curRadius, mCircleRadiusMax)), 90, 180, true, mPaint);
} else if (drawRight) {
mPaint.setColor(mCircleColor);
canvas.drawArc(getArcRecF(Math.min(curRadius, mCircleRadiusMax)), -90, 180, true, mPaint);
}

//为了动画,需要一直改变绘制的半径
if (curRadius < maxRadius) {
curRadius += mRadiusDrawStep;
invalidateSelf();
}

//设置普通的背景
button.setBackground(new CircleAnimDrawable().setPosition(CircleAnimDrawable.POS_LEFT));
button.setBackground(new CircleAnimDrawable().setPosition(CircleAnimDrawable.POS_CENTER));
button.setBackground(new CircleAnimDrawable().setPosition(CircleAnimDrawable.POS_RIGHT));

//如果要在RadioButton里面使用,需要包一层Drawable
private Drawable createRadioBackground(int position) {
StateListDrawable listDrawable = new StateListDrawable();
listDrawable.addState(new int[]{android.R.attr.state_checked}, new CircleAnimDrawable().setPosition(position));
return listDrawable;
}