如何根据EditText的改变监听TextView中文本的改变

public class myActivity extends Activity{

 private EditText content;

@Override
 protected void onCreate(Bundle savedInstanceState) {
  // TODO Auto-generated method stub
  super.onCreate(savedInstanceState);
  setContentView(R.Layout.main);

content = (EditText) findViewById(R.id.content);

content.setFilters(new InputFilter[] { new InputFilter.LengthFilter(
    500) });//设置编辑框的输入长度
  content.addTextChangedListener(textWatcher);//监听编辑框内容的变化

textSwitcher= (TextView) findViewById(R.id.textSwitcher);

textSwitcher.setText("500剩余");

}

 private TextWatcher textWatcher = new TextWatcher() {

  @Override
  public void onTextChanged(CharSequence s, int start, int before,
    int count) {

   int switcherText = GlobalInfo.MAX_CONTENT_LEN
     - content.getText().toString().length();

   textSwitcher.setText(String.valueOf(switcherText) + "剩余");
  }

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

  }

  @Override
  public void afterTextChanged(Editable s) {
   // TODO Auto-generated method stub

  }
 };
}