TextWatcher 를 이용해 입력되는 텍스트가 변경될때마다 이벤트 받아야겠는데요.
public class Hello extends Activity implements TextWatcher{
 EditText bbb;
 String[] aaa= {"aaa", "bbb", "ccc"};
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        bbb = (EditText)findViewById(R.id.text);
        bbb.addTextChangedListener(this);
    }

 @Override
 public void afterTextChanged(Editable s) {
  // TODO Auto-generated method stub
  String temp =  bbb.getText().toString();
   if(temp.equals(aaa[0])){
       Toast.makeText(getBaseContext(), temp, 500).show();
   }else if(temp.equals(aaa[1])){
    Toast.makeText(getBaseContext(), temp, 500).show();
   }else if(temp.equals(aaa[2])){
    Toast.makeText(getBaseContext(), temp, 500).show();
   }
 }
 @Override
 public void beforeTextChanged(CharSequence s, int start, int count,
   int after) {
  // TODO Auto-generated method stub
 }

 @Override
 public void onTextChanged(CharSequence s, int start, int before, int count) {
  // TODO Auto-generated method stub
 }
}