Android编程实现监听EditText变化的方法

et_pos.addTextChangedListener(new TextWatcher() {
  @Override
  public void onTextChanged(CharSequence s, int start, int before, int count){}
  @Override
  public void beforeTextChanged(CharSequence s, int start, int count, int after) {}
  @Override
  public void afterTextChanged(Editable s) {
    if (s.length() != 0) {
      clearPosition.setVisibility(View.VISIBLE);
    }else {
      clearPosition.setVisibility(View.INVISIBLE);
    }
  }
});