代码实现Layout android:layout_alignParentRight
例如：
android:id="@+id/account_option" android:layout_width="20px"
android:layout_height="20px" android:focusable="true"
android:src="@drawable/accountoptionbutton"
android:layout_alignParentRight="true" android:layout_marginRight="25px" />
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RelativeLayout rl = new RelativeLayout(this);
MarginLayoutParams mp = new MarginLayoutParams(20,20); //item的宽高
mp.setMargins(0, 0, 25, 0);//分别是margin_top那四个属性
LayoutParams lp = new LayoutParams(mp);
lp.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
Button bt = new Button(this);
bt.setLayoutParams(lp);
rl.addView(bt);