银行卡四位加空格

EditText et_cardNum = (EditText) findViewById(viewId);
        bankCardNumAddSpace(et_cardNum);

/**
* 银行卡四位加空格
* @param mEditText
*/
protected void bankCardNumAddSpace(final EditText mEditText){
mEditText.addTextChangedListener(new TextWatcher() {
   int beforeTextLength=0;
   int onTextLength=0;
   boolean isChanged = false;
   
   int location=0;//记录光标的位置
private char[] tempChar;
private StringBuffer buffer = new StringBuffer();
int konggeNumberB = 0;

@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
beforeTextLength = s.length();
if(buffer.length()>0){
buffer.delete(0, buffer.length());
}
konggeNumberB = 0;
for (int i = 0; i < s.length(); i++) {
if(s.charAt(i) == ' '){
konggeNumberB++;
}
}
}

@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
onTextLength = s.length();
buffer.append(s.toString());
if(onTextLength == beforeTextLength || onTextLength <= 3 || isChanged){
isChanged = false;
return;
}
isChanged = true;
}

@Override
public void afterTextChanged(Editable s) {
if(isChanged){
location = mEditText.getSelectionEnd();
int index = 0;
while (index < buffer.length()) {
if(buffer.charAt(index) == ' '){
buffer.deleteCharAt(index);
}else{
index++;
}
}

index = 0;
int konggeNumberC = 0;
while (index < buffer.length()) {
if((index == 4 || index == 9 || index == 14 || index == 19)){
buffer.insert(index, ' ');
konggeNumberC++;
}
index++;
}

if(konggeNumberC>konggeNumberB){
location+=(konggeNumberC-konggeNumberB);
}

tempChar = new char[buffer.length()];
buffer.getChars(0, buffer.length(), tempChar, 0);
String str = buffer.toString();
if(location>str.length()){
location = str.length();
}else if(location < 0){
location = 0;
}

mEditText.setText(str);
Editable etable = mEditText.getText();
Selection.setSelection(etable, location);
isChanged = false;
}
}
});
}