主要要使用一个正则过滤即可实现：

        String regular = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
        mXEditText.setKeyListener(new DigitsKeyListener() {
            @Override
            public int getInputType() {
                return InputType.TYPE_TEXT_VARIATION_PASSWORD;
            }

            @Override
            protected char[] getAcceptedChars() {
                char[] ac = regular.toCharArray();
                return ac;
            }
        });