android - How to inflate Button to LinearLayout progmatically in this case? -

my task generate several amount of buttons fixed width , height.i decided store these buttons in arraylist use in future. how it:

 for(int = 1 ; i<=n; i++) {  button place = new button(this.context) ;        place.settextcolor(contextcompat.getcolor      (this.context,r.color.background_color));      place.settypeface(typefaceforplaces);      place.setid(i+0);      place.setbackgroundresource(r.drawable.real_place_background);      place.setlayoutparams(new      linearlayout.layoutparams(65,65));      places.add(place);  } 

but problem here place.setlayoutparams(newlinearlayout.layoutparams(65,65));

here,width , height set in pixels. need dp. know code converts dp pixels, not think solution. now,i have idea create layout , store there button's shape. here layout called place_button.xml:

    <?xml version="1.0" encoding="utf-8"?>    <button      xmlns:android="http://schemas.android.com/apk/res/android"         android:id="@+id/button_id"     android:layout_width="50dp"      android:layout_height="50dp"     android:background="@drawable/real_place_background"     android:textcolor="#202020">     </button> 

and created view , inflated button view. after that, got button above id , save button,because need lot of such buttons. needed change new button's id. got following error:

java.lang.runtimeexception: unable start activity componentinfo{com.incubic.abay.clasico/com.incubic.abay.clasico.gameactivity}: java.lang.nullpointerexception: attempt invoke virtual method 'void android.widget.button.setid(int)' on null object reference 

below code:

 private void generateplaces() {         view place_view = layoutinflater.from(getcontext()).inflate(r.layout.place_button,null);         for(int = 1 ; i<=n; i++)         {              button place = (button)place_view.findviewbyid(r.id.button_id);             place.setid(i+0);             place.settypeface(typefaceforplaces);             places.add(place) ;            }     } 

everything happens in fragment. generateplaces method called after onviewcreated. how solve problem?

probably have issue due absence of button id

<?xml version="1.0" encoding="utf-8"?> <button         xmlns:android="http://schemas.android.com/apk/res/android"         android:id="@+id/button_id"         android:layout_width="50dp"         android:layout_height="50dp"         android:background="@drawable/real_place_background"         android:textcolor="#202020"/> 

update:

when inflation, button view, no need findviewbyid.

in general don't think inflating view in case approach. better create buttons:

private void generateplaces() {     (int = 1; <= n; i++)     {         button place = new button(this.context);          place.settextcolor(contextcompat.getcolor(this.context, r.color.background_color));         place.settypeface(typefaceforplaces);         place.setid(i + 0);         place.setbackgroundresource(r.drawable.real_place_background);         place.setlayoutparams(new linearlayout.layoutparams(dptopx(50), dptopx(50)));          places.add(place);      } }  private int dptopx(int dp) {     return (int) (dp * resources.getsystem().getdisplaymetrics().density); }