EditeText的maxlength中文、字符长度限制

一直以为在xml布局文件中对EditText添加 android:maxLength="30";属性是控制EditText字符数的。想当然的以为一个中文占2个字符，一个英文占1个字符。结果的结果当然不是了。

确切的说来android:maxLength="30"是对EditText的字数进行控制的。不管中文还是英文。都是30个字。这下麻烦了，查了整个API就没发现有真正是对字符进行控制的。最后发现只能用自定义的InputFilter来实现

package com.example.inputfilterdemo;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.text.InputFilter;
import android.text.Spanned;
import android.text.TextWatcher;
import android.util.Log;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

/**
*
* ClassName:MainActivity
*
* @author Jerome Song
* @version
* @since Ver 1.1
* @Date 2013 2013-4-4 下午2:55:42
*
* @see
*/
public class MainActivity extends Activity {

private EditText etTest;

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
init();
}

private void init() {
etTest = (EditText) findViewById(R.id.et_test);
InputFilter[] filters = { new NameLengthFilter(16) };
etTest.setFilters(filters);
}

private class NameLengthFilter implements InputFilter {
int MAX_EN;// 最大英文/数字长度 一个汉字算两个字母
String regEx = "[\\u4e00-\\u9fa5]"; // unicode编码，判断是否为汉字

public NameLengthFilter(int mAX_EN) {
super();
MAX_EN = mAX_EN;
}

@Override
public CharSequence filter(CharSequence source, int start, int end,
Spanned dest, int dstart, int dend) {
int destCount = dest.toString().length()
+ getChineseCount(dest.toString());
int sourceCount = source.toString().length()
+ getChineseCount(source.toString());
if (destCount + sourceCount > MAX_EN) {
Toast.makeText(MainActivity.this, getString(R.string.count),
Toast.LENGTH_SHORT).show();
return "";

} else {
return source;
}
}

private int getChineseCount(String str) {
int count = 0;
Pattern p = Pattern.compile(regEx);
Matcher m = p.matcher(str);
while (m.find()) {
for (int i = 0; i <= m.groupCount(); i++) {
count = count + 1;
}
}
return count;
}
}

}