EditText为空时单击按钮时应用程序崩溃

Question

String mobile = edtMobile.getText().toString();
            String password = edtPassword.getText().toString();
            String phone = String.valueOf(mobile);
            char c  = phone.charAt(0);

                if (mobile.length() > 0&& mobile.length() == 10) {
                    if (phone.length()> 0  && c == '8' || c == '9' || c == '7') {
                        if (password.length() > 0 && password.length() < 4 && password.length() > 15) {
                        } else {
                            Toast.makeText(AuthenticationActivity.this, "Password Character Must Be Between 4 - 15", Toast.LENGTH_SHORT).show();
                        }
                    } else {
                        Toast.makeText(AuthenticationActivity.this, "Number Must Begin with 9 8 7", Toast.LENGTH_SHORT).show();
                        return;
                    }
                } else {
                    Toast.makeText(AuthenticationActivity.this, "Enter Only 10 Digit Number", Toast.LENGTH_SHORT).show();
                    return;
                }

Answer 1

“IndexOutOfBounds”异常的原因

当您试图获取边界中并不真正存在的索引值时（在您的例子中，长度为'phone'字符串，为null）会出现此异常。因此，当您试图获取索引'0'处的值时，它会引发异常。

解决方案

if(phone!=null && !phone.isEmpty()) {
    char c  = phone.charAt(0);
}