Unable to parsing got Null pointer Exception
问题 et2.addTextChangedListener(new TextWatcher() { @Override public void onTextChanged(CharSequence s, int start, int before, int count) { // TODO Auto-generated method stub et2 = (EditText) findViewById(R.id.editText2); area = Math.PI * radius * radius; String name = Double.toString(area); et2.setText(name); } @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) { // TODO Auto-generated method stub } @Override public void afterTextChanged(Editable s) { // TODO