android修改layout的形状 用代码方式非xml方式

RelativeLayout loginForm  = newRelativeLayout(context);
RelativeLayout.LayoutParams loginFormLayout = newRelativeLayout.LayoutParams(LayoutParams.FILL_PARENT, 200);
loginForm.setLayoutParams(loginFormLayout);
....
int radius = 15;
float[] outerR = new float[] { radius, radius, radius, radius,radius, radius, radius, radius };
RoundRectShape roundRectShape = new RoundRectShape(outerR,null, null);  // 构造一个圆角矩形,可以使用其他形状，这样ShapeDrawable就会根据形状来绘制。
//RectShape rectShape = new RectShape(); //如果要构造直角矩形可以
ShapeDrawable shapeDrawable = newShapeDrawable(roundRectShape); //组合圆角矩形和ShapeDrawable
shapeDrawable.getPaint().setColor(0xffC0C0C0);       //设置形状的颜色
shapeDrawable.getPaint().setStyle(Paint.Style.FILL);  // 设置绘制方式为填充
loginForm.setBackgroundDrawable(shapeDrawable);