【android】EditText输入银行卡号每四位空一格

完美仿微信银行卡号输入，输入每4个数字就自动添加一个空格

代码如下：

import android.text.Editable;
import android.text.Selection;
import android.text.TextWatcher;
import android.widget.EditText;

/**
* Bank card input TextWatcher
* 4 grouping input
* Please set EditText max length is 26
* Created by cc_want on 2017/7/13.
*/
public class BankCardTextWatcher implements TextWatcher {

//default max length = 21 + 5 space
private static final int DEFAULT_MAX_LENGTH = 21 + 5;
//max input length
private int maxLength = DEFAULT_MAX_LENGTH;
private int beforeTextLength = 0;
private boolean isChanged = false;

//space count
private int space = 0;

private StringBuffer buffer = new StringBuffer();
private EditText editText;

public static void bind(EditText editText){
new BankCardTextWatcher(editText,DEFAULT_MAX_LENGTH);
}
public static void bind(EditText editText,int maxLength){
new BankCardTextWatcher(editText,maxLength);
}
public BankCardTextWatcher(EditText editText,int maxLength){
this.editText = editText;
this.maxLength = maxLength;
editText.addTextChangedListener(this);
}
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
beforeTextLength = s.length();
if (buffer.length() > 0) {
buffer.delete(0, buffer.length());
}
space = 0;
for (int i = 0; i < s.length(); i++) {
if (s.charAt(i) == ' ') {
space ++;
}
}
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
int length = s.length();
buffer.append(s.toString());
if (length == beforeTextLength || length <= 3
|| isChanged) {
isChanged = false;
return;
}
isChanged = true;
}
@Override
public void afterTextChanged(Editable s) {
if (isChanged) {
int selectionIndex = editText.getSelectionEnd();
//total char length
int index = 0;
while (index < buffer.length()) {
if (buffer.charAt(index) == ' ') {
buffer.deleteCharAt(index);
} else {
index ++;
}
}
//total space count
index = 0;
int totalSpace = 0;
while (index < buffer.length()) {
if ((index == 4 || index == 9 || index == 14 || index == 19 || index == 24)) {
buffer.insert(index, ' ');
totalSpace ++;
}
index++;
}
//selection index
if (totalSpace > space) {
selectionIndex += (totalSpace - space);
}
char[] tempChar = new char[buffer.length()];
buffer.getChars(0, buffer.length(), tempChar, 0);
String str = buffer.toString();
if (selectionIndex > str.length()) {
selectionIndex = str.length();
} else if (selectionIndex < 0) {
selectionIndex = 0;
}
editText.setText(str);
Editable text = editText.getText();
//set selection
Selection.setSelection(text, selectionIndex < maxLength ? selectionIndex : maxLength);
isChanged = false;
}
}
}

一般银行卡号最长21位，再加上中间的5个空格，所以我们设置EditText的最大可输入长度为26

使用方法如下：
1.设置EditText的最大可输入长度为26

<EditText
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="请输入您的卡号"
android:inputType="number"
android:maxLength="26"
android:singleLine="true" />

2.添加EditText输入监听

BankCardTextWatcher.bind(mEdtBankCardNo);