A320 ACFT IN CRUISE HAD LOW INTEGRATED DRIVE GENERATOR OIL PRESSURE. INTEGRATED DRIVE GENERATOR WAS SECURED IN ACCORDANCE WITH ECAM PROCS. ALMOST IMMEDIATELY A 'NAV ADR 1 FAULT' ANNUNCIATED AND FLC FOLLOWED PROCS TO SELECT #3 ADR FOR CAPT'S POS. AS FLC TURNED OFF THE #1 ADR; BOTH PFD'S WENT BLANK; LOST FLT DIRECTORS; AUTOTHRUST; AIRSPD AND ALT REF. FLC SELECTED #1 ADR BACK AND DISPLAY RETURNED; BUT AUTOPLT WAS LOST. RPTR SAYS ACFT WAS IN ALT LAW WITH PROTECTIONS LOST. EMER DECLARED AND FLT CONTINUED TO DEST.

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DEPARTED MCI TO DTW. WX AT MCI RAIN; WINDS GUSTY OUT OF THE E WITH TSTMS IN THE AREA. TKOF WAS NORMAL; ALONG WITH THE CLB PHASE. UPON LEVELOFF WE RECEIVED AN INTEGRATED DRIVE GENERATOR FAULT ON THE #1 ENG (INTEGRATED DRIVE GENERATOR LOW PRESSURE). THE ECAM AND COM PROCS WERE FOLLOWED AND THE #1 INTEGRATED DRIVE GENERATOR WAS SECURED. WITHIN 1 MIN AFTER RECEIVING THE INTEGRATED DRIVE GENERATOR FAULT MESSAGE; A SECOND MESSAGE APPEARED 'NAV ADR 1 FAULT.' THE ECAM AND COM PROCS CALLS FOR THE AIR DATA SWITCH TO BE MOVED TO CAPT #3 POS.' THIS WAS ACCOMPLISHED. THE NEXT STEP IN THE PROC CALLED FOR THE #1 ADR SWITCH TO OFF; WITH THE CAPT RECEIVING AIR DATA INFO FROM ADR #3 AND THE FO TO RECEIVE AIR DATA FROM ADR #2. WHEN THIS STEP WAS ACCOMPLISHED THE CAPT AND FO PFD WENT BLANK -- IN THAT WE LOST OUR FLT DIRECTORS; AUTOTHRUST; AIRSPD INDICATOR; ALT INDICATOR. WE BROUGHT ADR #1 BACK ON LINE TO RECOVER THOSE LOST ITEMS DESCRIBED ABOVE. DISPATCH AND MAINT WERE ADVISED. THE ACFT WAS IN ALT LAW WITH PROTECTIONS LOST. AN EMER WAS DECLARED. PROCEEDED TO DTW BECAUSE THE WX THERE WAS CLR. LNDG WAS NORMAL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR FO SPECULATES THAT; SINCE THE ACFT HAD JUST COME FROM MAINT; THAT PERHAPS THE PROBS THEY EXPERIENCED HAD SOMETHING TO DO WITH FAULTY MAINT. FOR EXAMPLE; THE INTEGRATED DRIVE GENERATOR LOW OIL PRESSURE MAY HAVE BEEN A RESULT OF IMPROPER SVCING AND THE ADR FAULTS FROM SOME OTHER FLAW. BECAUSE THE CFDS READOUT ON POSTFLT INDICATED A TAT FAULT; MAINT BELIEVES THE ADR PROBS WERE A RESULT OF FAULTY INPUT FROM THE TAT. RPTR FO WAS FLYING AT THE TIME OF THE ADR PROB AND; WHEN ALL SCREENS WENT BLANK WITH THE ONLY FLT INSTS AVAILABLE THE STANDBY INSTS; THE FO ASKED THE CAPT TO TURN BACK ON THE #1 ADR. TURNING OFF THE #1 ADR WAS THE ACTION WHICH CAUSED LOSS OF THE PFD; FLT DIRECTOR; AIRSPD; ALT AND AUTOPLT. RPTR SAYS THAT THEY WERE NEVER ABLE TO GET THE AUTOPLT BACK; BUT THE REST OF THE DISPLAYS APPEARED NORMAL; THOUGH THE ACFT WAS IN ALT LAW WITH PROTECTIONS LOST. THE FLC COORDINATED WITH THEIR MAINT AND DISPATCH. BECAUSE THE WX WAS POOR AT DEP ARPT AND GOOD AT THE DEST ARPT; IT WAS DECIDED TO CONTINUE. TO DATE THE FLC HAS HAD NO SPECIFIC FEEDBACK ON THE EXACT CAUSE OF THE INCIDENT.