我有两个微调器，一个带国家列表（countrySpinner），另一个带省列表（stateSpinner）。我希望仅当在countrySpinner上选择了“尼日利亚”时才使stateSpinner处于活动状态，而其他国家也可以不选择stateSpinner上的项目而处于活动状态。当我在countrySpinner和相应的状态上选择“尼日利亚”时，我的代码可以正常工作，但是我得到此NullPointerException：每当我在countrySpinner上选择尼日利亚以外的国家时，println都需要一条消息。不太确定如何通过这里。我将不胜感激任何帮助。我的代码如下。enter code here
public class RegisterActivity extends AppCompatActivity {
Spinner countrySpinner, stateSpinner;
List<String> countryList;
ArrayList<String> stateList;
ArrayAdapter<String> stateAdapter;
String countrySelected, stateSelected, gender;
TextInputLayout name, email, password, confirmPw;
RadioGroup genderOptionGroup;
RadioButton genderOptionBtn;
TextView countryUnCheckedWarning;
Button nextButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);nextButton = findViewById(R.id.createAccNext);
countryUnCheckedWarning = findViewById(R.id.countrySelectW);
genderOptionGroup = findViewById(R.id.gender_group);
name = findViewById(R.id.fullNameInputLayout);
email = findViewById(R.id.emailInputLayout);
password = findViewById(R.id.pwInputLayout);
confirmPw = findViewById(R.id.cpwInputLayout);
countrySpinner = findViewById(R.id.countryDropDown);
stateSpinner = findViewById(R.id.stateDropDown);
stateList = new ArrayList<String>(Arrays.asList("Select State of Residence", "Abia", "Abuja", "Adamawa", "Akwa Ibom", "Anambra",
"Bauchi", "Bayelsa", "Benue", "Borno", "Cross River", "Delta", "Ebonyi", "Enugu", "Edo",
"Ekiti", "Gombe", "Imo", "Jigawa", "Kaduna", "Kano", "Katsina", "Kebbi", "Kogi", "Kwara",
"Lagos", "Nasarawa", "Niger", "Ogun", "Ondo", "Osun", "Oyo", "Plateau", "Rivers", "Sokoto",
"Taraba", "Yobe", "Zamfara", "Territory"));
stateAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, stateList);
stateAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
stateSpinner.setAdapter(stateAdapter);
countryList = new ArrayList<String>();
countryList.add(0, "Select Country");
countryList.add("Gambia");
countryList.add("Sierra Leone");
countryList.add("Liberia");
countryList.add("Ghana");
countryList.add("Nigeria");
countryList.add("South Africa");
ArrayAdapter<String> countryAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, countryList);
countryAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
countrySpinner.setAdapter(countryAdapter);
// Country Spinner
countrySpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
if (!(parent.getItemAtPosition(position).equals("Nigeria")) && !(parent.getItemAtPosition(position).equals("Select Country"))){
// Country other than Nigeria has been selected
countrySelected = parent.getItemAtPosition(position).toString();
Log.i("Country Selected is",countrySelected);
nextButton.setEnabled(true);
nextButton.setBackgroundColor(getResources().getColor(R.color.red));
}else if (parent.getItemAtPosition(position).equals("Nigeria")){
// Nigeria is selected
stateSpinner.setAlpha(1);
countrySelected = "Nigeria";
nextButton.setEnabled(false);
nextButton.setBackgroundColor(getResources().getColor(R.color.silverash));
}else {
countrySelected = "";
nextButton.setEnabled(false);
nextButton.setBackgroundColor(getResources().getColor(R.color.silverash));
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
// State SpinnerGroup
stateSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
if (parent.getItemAtPosition(position).equals("Select State of Residence")) {
nextButton.setEnabled(false);
nextButton.setBackgroundColor(getResources().getColor(R.color.silverash));
} else {
stateSelected = parent.getItemAtPosition(position).toString();
nextButton.setEnabled(true);
nextButton.setBackgroundColor(getResources().getColor(R.color.red));
Log.i("State Selected", stateSelected);
}
}
@Override
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
// Name, Email and Password Validation MTDs Below
private boolean validateName() {
String nameInpute = name.getEditText().getText().toString().trim();
// check for non empty field
if (nameInpute.isEmpty()) {
name.setError("Name Field Can't be empty");
return false;
} else if (nameInpute.length() < 5) {
name.setError("Name is too short");
return false;
} else {
name.setError(null);
return true;
}
}
private boolean validateEmail() {
String emailInpute = email.getEditText().getText().toString().trim();
// Now we check for non empty field
if (emailInpute.isEmpty()) {
email.setError("E-mail Field Can't be empty");
return false;
} else if (!Patterns.EMAIL_ADDRESS.matcher(emailInpute).matches()) {
email.setError("Please enter a valid email address");
return false;
} else {
// Remove Error and return true
email.setError(null);
return true;
}
}
private boolean validatePassword() {
String passwordInpute = password.getEditText().getText().toString().trim();
// check for non empty field
if (passwordInpute.isEmpty()) {
password.setError("Password Field Can't be empty");
return false;
} else if (passwordInpute.length() > 15) {
password.setError("Password is too long");
return false;
} else {
password.setError(null);
return true;
}
}
private boolean validateCPassword() {
String passwordInpute = password.getEditText().getText().toString().trim();
String confirmPWInpute = confirmPw.getEditText().getText().toString().trim();
// check for non empty field
if (confirmPWInpute.isEmpty()) {
confirmPw.setError("Password Field Can't be empty");
return false;
} else if (!confirmPWInpute.equals(passwordInpute)) {
confirmPw.setError("Password does not match");
return false;
} else {
password.setError(null);
return true;
}
}
public void moveToNextOnReg(View view) {
// check for or validations
if (!validateName() | !validateEmail() | !validatePassword() | !validateCPassword()) {
return; }
// put whatever result needed here
String fullName = name.getEditText().getText().toString().trim();
String emailRegistered = email.getEditText().getText().toString().trim();
String passwordRegistered = password.getEditText().getText().toString().trim();
Log.i("Name", fullName);
Log.i("E-mail", emailRegistered);
Log.i("Password", passwordRegistered);
Log.i("Country", countrySelected);
Log.i("State", stateSelected);
Log.i("Sex", gender);
Intent intentNext = new Intent(getApplicationContext(),ToNextActivity.class);
startActivity(intentNext);
}
public void backToOnboarding(View view) {
Intent intent = new Intent(getApplicationContext(), OnboardingActivity.class);
startActivity(intent);
finish();
}
public void onGenderSelected(View view){
int radioId = genderOptionGroup.getCheckedRadioButtonId();
genderOptionBtn = findViewById(radioId);
gender = genderOptionBtn.getText().toString();
Log.i("Gender Selceted", genderOptionBtn.getText().toString());
}
}
您似乎没有在nextButton中初始化onCreate()：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);nextButton = findViewById(R.id.createAccNext);
countryUnCheckedWarning = findViewById(R.id.countrySelectW);
genderOptionGroup = findViewById(R.id.gender_group);
name = findViewById(R.id.fullNameInputLayout);
email = findViewById(R.id.emailInputLayout);
password = findViewById(R.id.pwInputLayout);
confirmPw = findViewById(R.id.cpwInputLayout);
countrySpinner = findViewById(R.id.countryDropDown);
stateSpinner = findViewById(R.id.stateDropDown);
//here.....
nextButton = findViewById(...............);//what ever the id is in xml