Android GridLayout- cover whole screen programmatically -

i want grid layout cover whole screen , want programmatically. when in static xml adding app:layout_columnweight attribute, looks want have follows:

but when tried create same layout programmatically, looks this:

i want same first image. here code:

public class mainactivity extends appcompatactivity {  @override protected void oncreate(bundle savedinstancestate) {     super.oncreate(savedinstancestate);     android.support.v7.widget.gridlayout gridlayout = new android.support.v7.widget.gridlayout(this);     gridlayout.setlayoutparams(new linearlayout.layoutparams(linearlayout.layoutparams.match_parent, linearlayout.layoutparams.wrap_content));     gridlayout.setcolumncount(3);     (int = 0; < 9; i++) {         button button = new button(mainactivity.this);         gridlayout.layoutparams lp = (gridlayout.layoutparams) button.getlayoutparams();          if (lp == null) {             lp = new gridlayout.layoutparams();         }         lp.columnspec = gridlayout.spec(gridlayout.undefined, 1, 1f);         button.setlayoutparams(lp);         button.settext("button " + (i + 1));         gridlayout.addview(button);     }     linearlayout linearlayout = new linearlayout(this);     linearlayout.addview(gridlayout);     setcontentview(linearlayout); } } 

please me. note- using min sdk 21.

update- here xml code

<linearlayout  xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" android:layout_width="match_parent" android:layout_height="match_parent">  <android.support.v7.widget.gridlayout     android:layout_width="match_parent"     android:layout_height="wrap_content"     app:columncount="3">      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 1" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 2" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 3" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 4" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 5" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 6" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 7" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 8" />      <button         android:layout_width="wrap_content"         android:layout_height="wrap_content"         app:layout_columnweight="1"         app:layout_gravity="fill"         android:text="button 9" /> </android.support.v7.widget.gridlayout> </linearlayout> 

replace activity with:

 public class mainactivity extends appcompatactivity {   @override  protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.your_layout_name);  } }