一： 宣告控制元件。

         TextView hasnumTV;

        TextView hasnum;// 用來顯示剩餘字數

        int num = 50;// 限制的最大字數

二： 主要的方法：

  hasnumTV = (TextView) findViewById(R.id.tv_num);

                hasnumTV.setText("限" + num + "" + "字以內");

                editText.addTextChangedListener(new TextWatcher() {

                        private CharSequence temp;

                        private int selectionStart;

                        private int selectionEnd;

                        @Override

                        public void onTextChanged(CharSequence s, int start, int before,

                                        int count) {

                        }

                        public void beforeTextChanged(CharSequence s, int start, int count,

                                        int after) {

                                temp = s;

                        }

                        public void afterTextChanged(Editable s) {

                                // TODO Auto-generated method stub

                                int number = num - s.length();

                                hasnumTV.setText("剩餘" + "" + number + "個字");

                                selectionStart = editText.getSelectionStart();

                                selectionEnd = editText.getSelectionEnd();

                                if (temp.length() > num) {

                                        s.delete(selectionStart - 1, selectionEnd);

                                        int tempSelection = selectionEnd;

                                        editText.setText(s);

                                        editText.setSelection(tempSelection);// 設定游標在最後

                                }

                        }

                });