why do I keep getting null exceptions at setOnClickListener

Why do I kee[ getting null errors at setOnClickListener?

R.layout.dataentry is the ContentView. It has the addRecord (a button) and it loads and displays fine. It looks as though R.id.addRecord gets an ID when I look in the debugger). I'm sure it has something to do with the ContentView not being loaded correctly resulting in a null pointer exception when I try to add the listenter, but I've tried preloading it several ways (here, earlier) and I can't figure out how to do it. I guess I'd prefer to have all my views cached so that I can add listeners early. Can someone help?

Thanks.

      exercise = (RadioGroup)this.findViewById(R.id.exerciseType);
         addRecord = (Button)this.findViewById(R.id.addRecord);
         amount = (TextView)this.findViewById(R.id.amount);
         datePerformed = (DatePicker)this.findViewById(R.id.datePerfomed);

public void loadAddEntry() {
            setContentView(R.layout.dataentry);
            addRecord.setOnClickListener(
                 new View.OnClickListener(){
   开发者_如何学运维                  public void onClick(View view) {
                         addRecordClicked();
                    }

                    ;});

            }

You are doing it the wrong way... you have something like:

exercise = (RadioGroup)this.findViewById(R.id.exerciseType);

Which I guess is on the onCreate method, and previous to those lines you should have another setContentView(R.layout.anotherstuff);. Then, you have a loadAddEntry method with setContentView(R.layout.dataentry);. So, here you have a problem: if you have already defined another contentview, why are you redefining it?