画一个倒三角形

public class ArrowView extends View{

	private Context mContext = null;
	
	@Override
	protected void onDraw(Canvas canvas) {
		Path path = new Path(); 
        path.moveTo(0, 0); 
        path.lineTo(getWidth(), 0); 
        path.lineTo(getWidth()/2, getHeight()); 
        path.lineTo(0, 0);
        ShapeDrawable circle = new ShapeDrawable(new PathShape(path, getWidth(), getHeight()));
        circle.getPaint().setColor(mContext.getResources().getColor(R.color.download_bg_menu));
        circle.setBounds(0, 0, getWidth(), getHeight());
        circle.draw(canvas);
		super.onDraw(canvas);
	}

	public ArrowView(Context context, AttributeSet attrs) {
		super(context, attrs);
		mContext = context;
	}

}