java - Android - difference between static and dynamic button weight -

i'm working tablelayout, first row static (xml) , second row added during runtime. both layouts should visually equal. however, i'm getting different results:

row 1: [----a-----] [----------b----------] [-----c----] row 2: [-----a-----] [---------b---------] [-----c-----] 

here xml row 1:

<button  android:id="@+id/stat_a"  android:layout_width="0dp"  android:layout_weight="1"  android:text="a" /> 

the weight "1" buttons stat_a , stat_c, , "2" stat_b.

here java code row 2:

 button btn = new button(this);  btn.setid("dyn_a");  layoutparams btn_param = new tablerow.layoutparams(layoutparams.match_parent, layoutparams.match_parent, _dyn_weight_);  btn.setlayoutparams(btn_param);  btn.settext("a");  layout.addview(btn); 

the _dyn_weight_ "1" buttons dyn_a , dyn_c, , "2" dyn_b.

where mistake?

thanks!

edit

the full xml:

<tablelayout xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/tbl01"     xmlns:tools="http://schemas.android.com/tools"     android:layout_width="fill_parent"     android:layout_height="fill_parent"     tools:context=".mainactivity">      <tablerow         android:id="@+id/row1"         android:layout_width="match_parent"         android:layout_height="match_parent">            <button             android:id="@+id/stat_a"             android:layout_width="0dp"             android:layout_weight="1"             android:text="a" />          <button             android:id="@+id/stat_b"             android:layout_width="0dp"             android:layout_weight="2"             android:text="b" />          <button             android:id="@+id/stat_c"             android:layout_width="0dp"             android:layout_weight="1"             android:text="c" />      </tablerow>            <tablerow         android:id="@+id/row2"         android:layout_width="match_parent"         android:layout_height="match_parent">            </tablerow>  </tablelayout>