[java]
myEditText.setInputFilters(new InputFilter[]{
new InputFilter() {
@Override
filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
return dest.subSequence(dstart, dend);
}
}
});
那么到底是如何实现disable的呢？先来看看InputFilter接口实现类的介绍
InputFilter.AllCaps
--This filter will capitalize all the lower case letters that are added through edits
InputFilter.LengthFillter
--This filter will constrain edits not to make the length of the text greater than the specified length
NumberKeyListener
--For numeric text entry
DateKeyListener
--For entering dates in a text field
DateTimeKeyListener
--For entering dates and times in the same text field
DialerKeyListener
--For dialing-only text entry
DigitsKeyListener
--For digits-only text entry
TimeKeyListener
--For entering times in a text field
LoginFilter
--Abstract class for filtering login-related text (user names and passwords)
LoginFilter.PasswordFilterGMail
--This filter is compatible with GMail passwords which restricts characters to the Latin-1 (ISO8859-1) char set
LoginFilter.UsernameFilterGMail
--This filter rejects characters in the user name that are not compatible with GMail account creation
LoginFilter.UsernameFilterGeneric
--This filter rejects characters in the user name that are not compatible with Google login
可以看出，InputFilter主要是对用户的（输入）文本进行过滤的，这个接口只有一个filter方法
先看看InputFilter.AllCaps的实现原理
[java]
public static class AllCaps implements InputFilter {
public CharSequence filter(CharSequence source, int start, int end,
Spanned dest, int dstart, int dend) {
for (int i = start; i < end; i++) {
if (Character.isLowerCase(source.charAt(i))) {
char[] v = new char[end - start];
TextUtils.getChars(source, start, end, v, 0);
String s = new String(v).toUpperCase();
if (source instanceof Spanned) {
SpannableString sp = new SpannableString(s);
TextUtils.copySpansFrom((Spanned) source,
start, end, null, sp, 0);
return sp;
} else {
return s;
}
}
}
return null; // keep original
}
}
从代码不难发现，当字符串source中包含小写字母时，将其转换为大写字母然后返回，从而实现AllCaps。
再来看看InputFilter.LengthFillter的实现原理
[java]
public CharSequence filter(CharSequence source, int start, int end,
Spanned dest, int dstart, int dend) {
int keep = mMax - (dest.length() - (dend - dstart));
if (keep <= 0) {
return "";
} else if (keep >= end - start) {
return null; // keep original
} else {
keep += start;
if (Character.isHighSurrogate(source.charAt(keep - 1))) {
--keep;
if (keep == start) {
return "";
}
}
return source.subSequence(start, keep);
}
}
其中mMax是文本的长度上限，keep是mMax与当前text的长度的差值。
当keep小于0时，也就是文本已经超过长度上限时，返回""
当文本没超过长度上限时，返回null，保持文本原样不变（keep original）
最后一个else暂时可以不考虑
再来看看EditText是如何使用这个InputFilter的，其实InputFilter是在TextView中用到的，在TextView的se