最近在做一个输入扫描银行卡的需求，要求通过card.io这个开源的sdk扫描获得银行卡号，或者直接输入卡号。那么在输入卡号的过程中，需要每4个数字自动空一格，实现起来也比较简单，主要是实现一个TextWacher的接口，然后重写里面的beforeTextChanged()，onTextChanged()以及afterTextChanged()三个方法。主要代码如下

import android.text.Editable;

import android.text.Selection;

import android.text.TextWatcher;

import android.util.Log;

import android.widget.EditText;

public class SpaceText implements TextWatcher{

private String TAG = "SpaceText";

private EditText etSpace;

int beforeTextLength = 0;

int onTextLength = 0;

public SpaceText(EditText etSpace){

super();

this.etSpace = etSpace;

}

public String removeAllSpace(String str) {

String tmpstr=str.replace(" ","");

return tmpstr;

}

@Override

public void afterTextChanged(Editable s) {

// TODO Auto-generated method stub

String str = etSpace.getText().toString();

Log.d(TAG, "mEditText = " + removeAllSpace(str) + ".");

onTextLength = str.length();

Log.d(TAG, "beforeLen = " + beforeTextLength + "afterLen = " + onTextLength);

if (onTextLength > beforeTextLength) {

if (str.length() == 5 || str.length() == 10 || str.length() == 15 || str.length() == 20) {

etSpace.setText(new StringBuffer(str).insert(

str.length() - 1, " ").toString());

etSpace.setSelection(etSpace.getText()

.length());

Log.d(TAG, "selection = " +etSpace.getText()

.length());

}

} else {

if (str.startsWith(" ")) {

etSpace.setText(new StringBuffer(str).delete(

onTextLength - 1, onTextLength).toString());

etSpace.setSelection(etSpace.getText()

.length());

Log.d(TAG, "else start space");

}

}

}

@Override

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

int after) {

// TODO Auto-generated method stub

beforeTextLength = s.length();

}

@Override

public void onTextChanged(CharSequence s, int start, int before, int count) {

// TODO Auto-generated method stub

}

}

首先创建一个类实现TextWatcher接口，重载构造方法来接受一个EditText类型的etSpace数据，这样在主函数中的EditText的控件里只用加入TextWatcher SpaceText = new SpaceText(EditText)将EditText传进去，然后 EditText.addTextChangedListener(SpaceText)设置监听即可。

代码比较简单，就当做一个小总结了。