class EditChangedListener implements TextWatcher {
    private CharSequence temp;//监听前的文本
    private int editStart;//光标开始位置
    private int editEnd;//光标结束位置
    private final int charMaxNum = 10;
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
      if (DEBUG)
        Log.i(TAG, "输入文本之前的状态");
      temp = s;
    }
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
      if (DEBUG)
        Log.i(TAG, "输入文字中的状态，count是一次性输入字符数");
      mTvAvailableCharNum.setText("还能输入" + (charMaxNum - s.length()) + "字符");
    }
    @Override
    public void afterTextChanged(Editable s) {
      if (DEBUG)
        Log.i(TAG, "输入文字后的状态");
      /** 得到光标开始和结束位置 ,超过最大数后记录刚超出的数字索引进行控制 */
      editStart = mEditTextMsg.getSelectionStart();
      editEnd = mEditTextMsg.getSelectionEnd();
      if (temp.length() > charMaxNum) {
        Toast.makeText(getApplicationContext(), "你输入的字数已经超过了限制！", Toast.LENGTH_LONG).show();
        s.delete(editStart - 1, editEnd);
        int tempSelection = editStart;
        mEditTextMsg.setText(s);
        mEditTextMsg.setSelection(tempSelection);
      }
    }
};

mEditTextMsg.addTextChangedListener(new EditChangedListener());