android EditText 字数监听并显示

et_content.addTextChangedListener(new TextWatcher() {
            private CharSequence temp;
            private int selectionStart;
            private int selectionEnd;

            @Override
            public void onTextChanged(CharSequence s, int start, int before,
                    int count) {
                temp = s;
                System.out.println("s="+s);
            }

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count,
                    int after) {
            }

            @Override
            public void afterTextChanged(Editable s) {
                int number = num - s.length();
                tv_num.setText("" + number);
                selectionStart = et_content.getSelectionStart();
                selectionEnd = et_content.getSelectionEnd();
                //System.out.println("start="+selectionStart+",end="+selectionEnd);                if (temp.length() > num) {
                    s.delete(selectionStart - 1, selectionEnd);
                    int tempSelection = selectionStart;
                    et_content.setText(s);
                    et_content.setSelection(tempSelection);//设置光标在最后                }
            }
        });