android - Why the background of ProgressDialog doesn't set to the transparent? -

i want set ground transparent , have set following code in

styles.xml <style name="dialog" parent="@android:style/theme.dialog">               <item name="android:windowframe">@null</item>               <item name="android:windowisfloating">true</item>               <item name="android:windowcontentoverlay">@null</item>               <item name="android:windowanimationstyle">@android:style/animation.dialog</item>               <item name="android:windowsoftinputmode">stateunspecified|adjustpan</item>               <item name="android:windowbackground">@android:color/transparent</item>               <item name="android:windownotitle">true</item>          </style>  

and have use progressdialog following code in java file , in fragment.

activity activity = getactivity() ; mprogressdialog = new progressdialog(activity,r.style.dialog) ; mprogressdialog.setcancelable(false) ; mprogressdialog.show() ; 

but progress following picture , , doesn't has transparent background.

why background doesn't change transparent ?

create custom mytheme in values\styles.xml

<style name="mytheme" parent="android:theme.holo.dialog">     <item name="android:alertdialogstyle">@style/customalertdialogstyle</item>     <item name="android:windowbackground">@android:color/transparent</item>     <item name="android:textcolorprimary">#ffffff</item>      <item name="android:backgrounddimenabled">false</item>     <item name="android:textcolor">#ffffff</item>     <item name="android:textstyle">normal</item>     <item name="android:textsize">12sp</item> </style> 

and add customalertdialogstyle in values\styles.xml

 <style name="customalertdialogstyle"> <item name="android:bottombright">@android:color/transparent</item> <item name="android:bottomdark">@android:color/transparent</item> <item name="android:bottommedium">@android:color/transparent</item> <item name="android:centerbright">@android:color/transparent</item> <item name="android:centerdark">@android:color/transparent</item> <item name="android:centermedium">@android:color/transparent</item> <item name="android:fullbright">@android:color/transparent</item> <item name="android:fulldark">@android:color/transparent</item> <item name="android:topbright">@android:color/transparent</item> <item name="android:topdark">@android:color/transparent</item> </style> 

and set progressdialog like:

 pd = new progressdialog(getactivity(),r.style.mytheme);  pd.setcancelable(false);  pd.setprogressstyle(android.r.style.widget_progressbar_small);  pd.show();