little problem with ProgressDialog in android

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Java

Mobile

Android

Android4x

hi every one . i am using the ProgressDialog in my project , but i have a little with that ! indeed i use it when i want to redirect to other activities . but unfortunately when i come back to the first activity , it still works !
so how can i cancel the dialog after Redirecting to other activities ?!

ProgressDialog.show(this, "Loading ...", " pleas wait");
Intent i=new Intent(this,Content.class); 
i.putExtra("Actype", "news");
startActivity(i);