在我使用AlertDialog的按钮退出活动并通过主菜单重新输入相同的对话框之前，所有内容都按预期工作。
以下是我对AlertDialog：
AlertDialog.Builder builder = new AlertDialog.Builder(NewCustomerInfoActivity.this);
if (result.equals("{\"success\":true}")){
builder.setMessage("Yeni müşteri başarıyla kaydedildi.").setTitle("Kayıt Başarılı");
builder.setPositiveButton("Ana ekrana dön", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
Intent backToMainActivityIntent = new Intent(NewCustomerInfoActivity.this, MainActivity.class);
dialog.dismiss();
startActivity(backToMainActivityIntent);
}
});
} else {
builder.setMessage("Yeni müşteri kaydedilemedi.").setTitle("Kayıt Başarısız");
builder.setPositiveButton("Tamam", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
}
});
}
AlertDialog dialog = builder.create();
dialog.show();
如果删除上面的代码，一切正常。
整个活动如果有帮助：
public class NewCustomerInfoActivity extends AppCompatActivity {
String jCities;
ArrayList<City> cities;
ArrayList<String> cityStrings;
ArrayList<String> townStrings;
RadioButton personalRadioButton;
RadioButton corporateRadioButton;
Spinner citySpinner;
Spinner townSpinner;
String url;
int isPersComp = 1;
String cityString = "Adana";
int cityNo = 1;
String townString = "Aladağ";
int townNo = 1;
JSONObject json;
String deviceId;
User user;
String result;
Toast toast;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_new_customer_info);
deviceId = Settings.Secure.getString(this.getContentResolver(), Settings.Secure.ANDROID_ID);
user = (User) getIntent().getSerializableExtra("user");
url = getResources().getString(R.string.service_call_url) + "newCustomer/" + deviceId + "/" + user.getSecureSessionId() + "/";
// Kayıtlı şehir ve ilçeler okunur.
SharedPreferences prefs = getSharedPreferences("cities", MODE_PRIVATE);
jCities = prefs.getString("jCities", null);
if (!(jCities.isEmpty() || jCities == null)){
WebRequest webRequest = new WebRequest();
cities = webRequest.parseCities(jCities);
cityStrings = new ArrayList<String>();
for (City city : cities){
if (!cityStrings.contains(city.getCityName())){
cityStrings.add(city.getCityName());
}
}
}
// Tüzel - Şahıs radio butonlarının kendilerine dokunulması durumunda tepkileri belirlenir.
personalRadioButton = (RadioButton) findViewById(R.id.personalRadioButton);
corporateRadioButton = (RadioButton) findViewById(R.id.corporateRadioButton);
isPersComp = 1;
View.OnClickListener optionOnClickListener = new View.OnClickListener() {
@Override
public void onClick(View view) {
TextView taxOrIdNoTitleTextView = (TextView) findViewById(R.id.taxOrIdNoTitleTextView);
if (personalRadioButton.isChecked()){
taxOrIdNoTitleTextView.setText("TC Kimlik No:");
isPersComp = 1;
}
if (corporateRadioButton.isChecked()){
taxOrIdNoTitleTextView.setText("Vergi No:");
isPersComp = 0;
}
}
};
personalRadioButton.setOnClickListener(optionOnClickListener);
corporateRadioButton.setOnClickListener(optionOnClickListener);
// İl seçimi için spinner doldurulur.
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item, cityStrings);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
final Spinner citySpinner = (Spinner) findViewById(R.id.citySpinner);
citySpinner.setAdapter(adapter);
citySpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
cityString = citySpinner.getSelectedItem().toString();
cityNo = 1 + citySpinner.getSelectedItemPosition();
resetTownSpinner(cityNo);
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
}
// Şehir seçimi yapılınca çağırılan ve ilçe spinner'ını seçilen şehre göre dolduran fonksiyon.
public void resetTownSpinner(int cityCode){
townStrings = new ArrayList<String>();
for (City city : cities){
if (city.getCityCode() == cityCode){
townStrings.add(city.getTownName());
}
}
townSpinner = (Spinner) findViewById(R.id.townSpinner);
ArrayAdapter<String> townAdapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item, townStrings);
townSpinner.setAdapter(townAdapter);
townSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
townString = townSpinner.getSelectedItem().toString();
townNo = 1 + townSpinner.getSelectedItemPosition();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
}
// Kayıt butonuna basıldığında çağırılan fonksiyon.
public void saveNewCustomer (View view){
// JSON objesi oluşturulur.
json = new JSONObject();
try {
// JSON objesi kullanıcının girdiği değerlere göre doldurulur.
JSONObject jCustomer = new JSONObject();
jCustomer.put("LOGICALREF", 0);
jCustomer.put("CODE", "");
EditText definitionText = (EditText) findViewById(R.id.definitionText);
jCustomer.put("DEFINITION_", definitionText.getText().toString());
jCustomer.put("ISPERSCOMP", isPersComp);
EditText taxOrIdNoText = (EditText) findViewById(R.id.taxOrIdNoText);
if (isPersComp == 1){
jCustomer.put("TAXNR", "");
jCustomer.put("TCKNO", taxOrIdNoText.getText().toString());
} else {
jCustomer.put("TAXNR", taxOrIdNoText.getText().toString());
jCustomer.put("TCKNO", "");
}
EditText taxOfficeText = (EditText) findViewById(R.id.taxOfficeText);
String taxOfficeString = taxOfficeText.getText().toString();
if (taxOfficeString.isEmpty() || taxOfficeString == null){
jCustomer.put("TAXOFFICE", "TCKIMLIK");
} else {
jCustomer.put("TAXOFFICE", taxOfficeString);
}
EditText emailText = (EditText) findViewById(R.id.emailText);
jCustomer.put("EMAILADDR", emailText.getText().toString());
EditText address1Text = (EditText) findViewById(R.id.address1Text);
jCustomer.put("ADDR1", address1Text.getText().toString());
EditText address2Text = (EditText) findViewById(R.id.address2Text);
jCustomer.put("ADDR2", address2Text.getText().toString());
jCustomer.put("CITY", cityString);
jCustomer.put("CITYCODE", cityNo);
jCustomer.put("TOWN", townString);
jCustomer.put("TOWNCODE", townNo);
EditText inChargeText = (EditText) findViewById(R.id.inChargeText);
jCustomer.put("INCHARGE", inChargeText.getText().toString());
EditText nameText = (EditText) findViewById(R.id.nameText);
jCustomer.put("NAME", nameText.getText().toString());
EditText surnameText = (EditText) findViewById(R.id.surnameText);
jCustomer.put("SURNAME", surnameText.getText().toString());
EditText phoneNo1Text = (EditText) findViewById(R.id.phoneNo1Text);
jCustomer.put("TELNRS1", phoneNo1Text.getText().toString());
EditText phoneNo2Text = (EditText) findViewById(R.id.phoneNo2Text);
jCustomer.put("TELNRS2", phoneNo2Text.getText().toString());
json.put("data", jCustomer);
// JSON objesini server'a gönderen Thread başlatılır.
new postJSON().execute();
} catch (Exception e){
e.printStackTrace();
}
}
// JSON objesini server'a gönderen Thread.
private class postJSON extends AsyncTask<Void, Void, Void>{
ProgressDialog progressDialog;
protected void onPreExecute() {
super.onPreExecute();
progressDialog = new ProgressDialog(NewCustomerInfoActivity.this);
progressDialog.setMessage("Yeni müşteri kaydediliyor. Lütfen bekleyiniz.");
progressDialog.setCancelable(false);
progressDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
WebRequest webRequest = new WebRequest();
// JSON objesi string'e dönüştürülür ve linkin sonuna eklenir.
url = url + json.toString();
result = webRequest.getJson(url, true);
return null;
}
protected void onPostExecute(Void requestResult) {
super.onPostExecute(requestResult);
if (progressDialog.isShowing()) {
progressDialog.dismiss();
}
AlertDialog.Builder builder = new AlertDialog.Builder(NewCustomerInfoActivity.this);
// Server'dan dönen değer kontrol edilir.
if (result.equals("{\"success\":true}")){
builder.setMessage("Yeni müşteri başarıyla kaydedildi.").setTitle("Kayıt Başarılı");
builder.setPositiveButton("Ana ekrana dön", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
Intent backToMainActivityIntent = new Intent(NewCustomerInfoActivity.this, MainActivity.class);
dialog.dismiss();
startActivity(backToMainActivityIntent);
}
});
} else {
builder.setMessage("Yeni müşteri kaydedilemedi.").setTitle("Kayıt Başarısız");
builder.setPositiveButton("Tamam", new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int id) {
dialog.dismiss();
}
});
}
AlertDialog dialog = builder.create();
dialog.show();
}
}
}
同样，只要不使用AlertDialog就没有问题。没问题，除非您使用AlertDialog，然后尝试再次进入Activity，然后该应用停止工作。
logcat的：
07-27 13:14:16.113 28618-28618/eof.concrete E/AndroidRuntime: FATAL EXCEPTION: main
Process: eof.concrete, PID: 28618
java.lang.RuntimeException: Unable to start activity ComponentInfo{eof.concrete/eof.concrete.newCustomer.NewCustomerInfoActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String eof.concrete.classes.User.getSecureSessionId()' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6540)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String eof.concrete.classes.User.getSecureSessionId()' on a null object reference
at eof.concrete.newCustomer.NewCustomerInfoActivity.onCreate(NewCustomerInfoActivity.java:64)
at android.app.Activity.performCreate(Activity.java:6980)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
at android.app.ActivityThread.-wrap11(Unknown Source:0)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1593)
at android.os.Handler.dispatchMessage(Handler.java:105)
at android.os.Looper.loop(Looper.java:164)
at android.app.ActivityThread.main(ActivityThread.java:6540)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
答案 0 :(得分：1)
问题出在这一行而不是AlertDialog
user = (User) getIntent().getSerializableExtra("user");
在调用getIntent()之前，您需要确保您的活动是由意图创建的。
当您的活动被Android框架销毁并重新创建时，意图将为null。
如果intent中的用户对象是Activity功能的基础，那么你可以完成它。
Intent intent = getIntent();
if (intent != null){
user = (User) intent.getSerializableExtra("user");
if (user == null){
//handle null user
}
} else {
//here you can call finish() if the user is fundamental to your Activity
//or you must handle a possible nullable `User` object in the following code
finish();
return;
}
在你的AlertDialog中，如果你想简单地回到之前的Activity，你可以替换这段代码
Intent backToMainActivityIntent = new Intent(NewCustomerInfoActivity.this,
MainActivity.class);
dialog.dismiss();
startActivity(backToMainActivityIntent);
用这个
dialog.dismiss();
finish();