使用Android创建强大的密码生成器

Question

因此，我正在构建一个应用程序，它可以根据用户的规范生成一个强密码。UI的spec部分如下所示。

下面是MainActivity.java类中的onCreate。我尝试创建一些逻辑，如选中某个单选按钮时的if语句，以及选中复选框时向String变量添加允许的字符。视图对象都是全局的btw，但我不知道如何在用户设置的字符限制范围内，使用每个允许的字符中的至少一个来创建一个随机字符串。

代码如下：

private static int MAX_LENGTH;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        capitalLetter = (CheckBox) findViewById(R.id.capital_letter);
        lowercaseLetter = (CheckBox) findViewById(R.id.lowercase_letter);
        numbers = (CheckBox) findViewById(R.id.numbers);
        symbols = (CheckBox) findViewById(R.id.symbols);

        passGroup = (RadioGroup) findViewById(R.id.passRadioGroup);

        sizeFour = (RadioButton) findViewById(R.id.size_four);
        sizeEight = (RadioButton) findViewById(R.id.size_eight);
        sizeTwelve = (RadioButton) findViewById(R.id.size_twelve);
        sizeSixteen = (RadioButton) findViewById(R.id.size_sixteen);

        passHint = (EditText) findViewById(R.id.passwordHint);

        passShow = (TextView) findViewById(R.id.passwordDisplay);

        passGenerate = (Button) findViewById(R.id.passwordGenerate);
        passClear = (Button) findViewById(R.id.passwordClear);

        String allowedCharacters = "";

        // Determines the types of characters permitted when a check box is checked.
        if (capitalLetter.isChecked()) {allowedCharacters += "ABCDEFGHIJKLMNOPQRSTUVWXYZ";}
        if (lowercaseLetter.isChecked()) {allowedCharacters += "abcdefghijklmnopqrstuvwxyz";}
        if (numbers.isChecked()) {allowedCharacters += "0123456789";}
        if (symbols.isChecked()) {allowedCharacters += "!@#$%^&*()_-+=<>?/{}~|";}

        //Determines the length of the string based on which radio button the user has selected.
        int checkedRadioButtonId = passGroup.getCheckedRadioButtonId();

        if (checkedRadioButtonId == 1) {MAX_LENGTH = 4;}
        if (checkedRadioButtonId == 2) {MAX_LENGTH = 8;}
        if (checkedRadioButtonId == 3) {MAX_LENGTH = 12;}
        if (checkedRadioButtonId == 4) {MAX_LENGTH = 16;}
    }

Answer 1

关于生成随机字符串的基本思想：

private static final String ALLOWED_CHARACTERS ="0123456789qwertyuiopasdfghjklzxcvbnm";

private static String getRandomString(final int sizeOfPasswordString){
  final Random random=new Random();
  final StringBuilder sb=new StringBuilder(sizeOfPasswordString);

  for(int i=0;i<sizeOfRandomString;++i){
      sb.append(ALLOWED_CHARACTERS.charAt(random.nextInt(ALLOWED_CHARACTERS.length())));
    return sb.toString();
  }
}