question: public static boolean isInstalled ( PackageManager packageManager , String packageName ) { List < PackageInfo > packs = packageManager . getInstalledPackages ( 0 ) ; for ( int i = 0 ; i < packs . size ( ) ; i ++ ) { if ( TextUtils . equals ( packs . get ( i ) . packageName , packageName ) ) return true ; } return false ; }
target:  Checks if the app has been installed on the system.