如何过滤EditText的输入？

Question

我想过滤一个输入EditText,只允许数字和字母,首先我TextWatcher用来处理最后一个输入字符,但是当你移动光标或者你经过一些内容时EditText,这个方法失败了,现在我想知道有没有办法过滤非法输入并给用户一个反馈.

Answer 1

添加InputFilter到您的用户EditText并提供Toast给用户.此代码段将为您提供帮助.

 InputFilter filter = new 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.isLetterOrDigit(source.charAt(i))) { // Accept only letter & digits ; otherwise just return
                            Toast.makeText(context,"Invalid Input",Toast.LENGTH_SHORT).show();
                            return "";
                        }
                    }
                    return null;
                }

            };

        editText.setFilters(new InputFilter[] { filter });

Answer 2

你试过xml方式吗？它看起来像这样

<EditText 
  android:id="@+id/editText"
  android:inputType="text" 
  android:digits="0,1,2,3,4,5,6,7,8,9,*,qwertzuiopasdfghjklyxcvbnm" 
  android:hint="Only letters and numbers allowed.."
/>

Answer 3

适用于所有 Android 版本：

public static InputFilter getOnlyCharactersFilter() {
    return getCustomInputFilter(true, false, false);
}

public static InputFilter getCharactersAndDigitsFilter() {
    return getCustomInputFilter(true, true, false);
}

public static InputFilter getCustomInputFilter(final boolean allowCharacters, final boolean allowDigits, final boolean allowSpaceChar) {
    return new InputFilter() {
        @Override
        public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {
            boolean keepOriginal = true;
            StringBuilder sb = new StringBuilder(end - start);
            for (int i = start; i < end; i++) {
                char c = source.charAt(i);
                if (isCharAllowed(c)) {
                    sb.append(c);
                } else {
                    keepOriginal = false;
                }
            }
            if (keepOriginal) {
                return null;
            } else {
                if (source instanceof Spanned) {
                    SpannableString sp = new SpannableString(sb);
                    TextUtils.copySpansFrom((Spanned) source, start, sb.length(), null, sp, 0);
                    return sp;
                } else {
                    return sb;
                }
            }
        }

        private boolean isCharAllowed(char c) {
            if (Character.isLetter(c) && allowCharacters) {
                return true;
            }
            if (Character.isDigit(c) && allowDigits) {
                return true;
            }
            if (Character.isSpaceChar(c) && allowSpaceChar) {
                return true;
            }
            return false;
        }
    };
}

现在你可以像这样使用这个文件管理器：

 //Accept Characters Only
edit_text.setFilters(new InputFilter[]{getOnlyCharactersFilter()});

//Accept Digits and Characters
edit_text.setFilters(new InputFilter[]{getCharactersAndDigitsFilter()});

//Accept Digits and Characters and SpaceBar
edit_text.setFilters(new InputFilter[]{getCustomInputFilter(true,true,true)});