class EditChangedListener implements TextWatcher {
    private CharSequence temp;//監(jiān)聽前的文本
    private int editStart;//光標開始位置
    private int editEnd;//光標結束位置
    private final int charMaxNum = 10;
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
      if (DEBUG)
        Log.i(TAG, "輸入文本之前的狀態(tài)");
      temp = s;
    }
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
      if (DEBUG)
        Log.i(TAG, "輸入文字中的狀態(tài)，count是一次性輸入字符數(shù)");
      mTvAvailableCharNum.setText("還能輸入" + (charMaxNum - s.length()) + "字符");
    }
    @Override
    public void afterTextChanged(Editable s) {
      if (DEBUG)
        Log.i(TAG, "輸入文字后的狀態(tài)");
      /** 得到光標開始和結束位置 ,超過最大數(shù)后記錄剛超出的數(shù)字索引進行控制 */
      editStart = mEditTextMsg.getSelectionStart();
      editEnd = mEditTextMsg.getSelectionEnd();
      if (temp.length() > charMaxNum) {
        Toast.makeText(getApplicationContext(), "你輸入的字數(shù)已經超過了限制！", Toast.LENGTH_LONG).show();
        s.delete(editStart - 1, editEnd);
        int tempSelection = editStart;
        mEditTextMsg.setText(s);
        mEditTextMsg.setSelection(tempSelection);
      }
    }
};

mEditTextMsg.addTextChangedListener(new EditChangedListener());