我正在尝试实现一个 EditText，它将输入限制为仅 alpha 字符 [A-Za-z]。
我从这篇文章开始使用 InputFilter 方法。当我键入“a%”时，文本会消失，然后如果我按退格键，则文本是“a”。我已经尝试过过滤器功能的其他变体，例如使用正则表达式仅匹配 [A-Za-z] 有时会看到重复字符等疯狂行为，我将输入“a”然后输入“b”然后得到“aab”输入“c”得到“aabaabc”，然后按退格键得到“aabaabcaabaabc”！
这是到目前为止我正在使用的代码，我尝试过不同的方法。
EditText input = (EditText)findViewById( R.id.inputText );
InputFilter filter = new InputFilter() {
@Override
public CharSequence filter( CharSequence source, int start, int end, Spanned dest, int dstart, int dend ) {
//String data = source.toString();
//String ret = null;
/*
boolean isValid = data.matches( "[A-Za-z]" );
if( isValid ) {
ret = null;
}
else {
ret = data.replaceAll( "[@#$%^&*]", "" );
}
*/
/*
dest = new SpannableStringBuilder();
ret = data.replaceAll( "[@#$%^&*]", "" );
return ret;
*/
for( int i = start; i < end; i++ ) {
if( !Character.isLetter( source.charAt( i ) ) ) {
return "";
}
}
return null;
}
};
input.setFilters( new InputFilter[]{ filter } );
我完全被这个难住了，所以这里的任何帮助将不胜感激。
编辑： 好的，我已经对 InputFilter 做了很多试验并得出了一些结论，尽管没有解决问题。请参阅下面我的代码中的注释。我现在要试试 Imran Rana 的解决方案。
EditText input = (EditText)findViewById( R.id.inputText );
InputFilter filter = new InputFilter() {
// It is not clear what this function should return!
// Docs say return null to allow the new char(s) and return "" to disallow
// but the behavior when returning "" is inconsistent.
//
// The source parameter is a SpannableStringBuilder if 1 char is entered but it
// equals the whole string from the EditText.
// If more than one char is entered (as is the case with some keyboards that auto insert
// a space after certain chars) then the source param is a CharSequence and equals only
// the new chars.
@Override
public CharSequence filter( CharSequence source, int start, int end, Spanned dest, int dstart, int dend ) {
String data = source.toString().substring( start, end );
String retData = null;
boolean isValid = data.matches( "[A-Za-z]+" );
if( !isValid ) {
if( source instanceof SpannableStringBuilder ) {
// This works until the next char is evaluated then you get repeats
// (Enter "a" then "^" gives "a". Then enter "b" gives "aab")
retData = data.replaceAll( "[@#$%^&*']", "" );
// If I instead always returns an empty string here then the EditText is blanked.
// (Enter "a" then "^" gives "")
//retData = "";
}
else { // source is instanceof CharSequence
// We only get here if more than 1 char was entered (like "& ").
// And again, this works until the next char is evaluated then you get repeats
// (Enter "a" then "& " gives "a". Then enter "b" gives "aab")
retData = "";
}
}
return retData;
}
};
input.setFilters( new InputFilter[]{ filter } );