ListView Adapter Crash

ListView Adapter Crash

i'm developing my app for android with Android Studio, in this app i want
to do parse of a page html, and see the results in the listview, but i got
this error:
java.lang.NullPointerException
at android.widget.ArrayAdapter.init(ArrayAdapter.java:310)
at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:104)
at
com.megadown.megacodownloader.ParsingArrayAdapter.<init>(ParsingArrayAdapter.java:30)
at
com.megadown.megacodownloader.Tab_Search$ParsingPaginaWeb.onPostExecute(Tab_Search.java:256)
at
com.megadown.megacodownloader.Tab_Search$ParsingPaginaWeb.onPostExecute(Tab_Search.java:118)
at android.os.AsyncTask.finish(AsyncTask.java:631)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at
android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4898)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
at dalvik.system.NativeStart.main(Native Method)
09-08 02:46:26.289 3004-3004/? E/Launcher: Error finding setting,
default accessibility to not found: accessibility_enabled
And I' didn't capish why i got this error!! This is code of error of row:
adapter = new ParsingArrayAdapter(MainActivity.this, titoli,
descrizioni,immagini);
lista.setAdapter(adapter);