Package test.chr;

import android.R;
import android.R.id;
import android.R.layout;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class TestActivity extends Activity {
  /** Called when the activity is first created. */
  int counter;
  Button add, sub;
  TextView display;
     @Override
     …
     setContentView(R.layout.main); <---- Fehler
     add=(Button)findViewById(R.id.addB);<---- Fehler
     sub=(Button)findViewById(R.id.subB);<---- Fehler
     display =(TextView) findViewById(R.id.tvDisplay);<---- Fehler
     add.setOnClickListener(new View.OnClickListener() 
 …