限制EditText只能输入字母和数字

private EditText mEtCode;

mEtCode = (EditText) findViewById(R.id.et_code);

mEtCode.setKeyListener(new DigitsKeyListener() {
    @Override
    protected char[] getAcceptedChars() {
        return getResources().getString(R.string.can_only_input_number_alphabet).toCharArray();
    }

    @Override
    public int getInputType() {
        return InputType.TYPE_TEXT_VARIATION_VISIBLE_PASSWORD;//明文显示，InputType.TYPE_TEXT_VARIATION_PASSWORD密文显示

    }
});

string.xml
　　<string name="can_only_input_number_alphabet">qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890</string>