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; 
            } 
        });