[英]Android Retrofit : Wait for response
我正在我的应用程序中实施改造 2 以调用网络服务。 我的代码如下:
注册.java
ConnectionDetector connectionDetector = new ConnectionDetector(SignUpActivity.this);
if (connectionDetector.isConnectingToInternet()) {
ArrayList<HashMap<String, String>> arrayListCountryDetails = new ArrayList<>();
GetCountryList getCountryList = new GetCountryList();
arrayListCountryDetails = getCountryList.CallWebServiceForCountryDetails(this);
// The app should wait here till the above retrofit web service calling returns response
CountryDetailsAdapter countryDetailsAdapter = new CountryDetailsAdapter(SignUpActivity.this, arrayListCountryDetails);
spinnerCountryName.setAdapter(countryDetailsAdapter);
} else {
String message = "No internet connection.";
AlertDialog alertDialog = new AlertDialog.Builder(this).create();
alertDialog.setTitle(getResources().getString(R.string.app_name));
alertDialog.setMessage(message);
alertDialog.setCancelable(false);
alertDialog.setButton(AlertDialog.BUTTON_NEUTRAL, "OK",
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
alertDialog.show();
}
获取国家列表.java
public class GetCountryList {
ProgressDialog dialog;
APIService mAPIService;
ArrayList<HashMap<String, String>> arrayListCountryDetails;
public ArrayList<HashMap<String, String>> CallWebServiceForCountryDetails(final Context context) {
dialog = new ProgressDialog(context);
dialog.setMessage("Please wait...");
dialog.setCancelable(false);
dialog.show();
arrayListCountryDetails = new ArrayList<>();
mAPIService = ApiUtils.getAPIService();
mAPIService.getCountryDetails().enqueue(new Callback<CountryDetailsResponseModel>() {
@Override
public void onResponse(Call<CountryDetailsResponseModel> call, Response<CountryDetailsResponseModel> response) {
if (response.isSuccessful()) {
HashMap<String, String> cntDetails = new HashMap<>();
cntDetails.put("airLineID", "0");
cntDetails.put("airLineName", "Select Airline");
arrayListCountryDetails.add(cntDetails);
// Get response
try {
if (response.body().getStatus() == 200 && response.body().getMessage().equalsIgnoreCase("success")) {
for (int count = 0; count < response.body().getCountry().size(); count++) {
cntDetails = new HashMap<>();
String countryID = response.body().getCountry().get(count).getCountryId();
String countryName = response.body().getCountry().get(count).getCountryName();
cntDetails.put("countryID", countryID);
cntDetails.put("countryName", countryName);
arrayListCountryDetails.add(cntDetails);
}
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
} else {
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
}
} catch (Exception e) {
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
}
}
}
@Override
public void onFailure(Call<AirLineDetailsResponseModel> call, Throwable t) {
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
}
});
return arrayListCountryDetails;
}
}
当我执行代码时,我收到空指针异常错误:
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Spinner.setAdapter(android.widget.SpinnerAdapter)' on a null object reference
at com.abc.xyz.SignUpActivity.initializeScreen(SignUpActivity.java:176)
at com.abc.xyz.SignUpActivity.onCreate(SignUpActivity.java:147)
at android.app.Activity.performCreate(Activity.java:6575)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3121)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3278)
at android.app.ActivityThread.access$1000(ActivityThread.java:211)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1705)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6912)
at java.lang.reflect.Method.invoke(Native Method)
我知道这是因为微调器初始化执行发生在改造响应之前。
请建议我如何等待改造响应。 我需要在上面的代码中做哪些更改。 由于这个问题,我无法继续前进。 提前致谢。
非常粗略地执行以下操作。 我只是将必要的代码部分放在AsyncTask
方法中。 根据需要进行修改。
if (connectionDetector.isConnectingToInternet()) {
// The app should wait here till the above retrofit web service calling returns response
AsyncTask task = new AsyncTask<Void, Void, List<Map<String, String>>>() {
@Override
protected String doInBackground(Void... params) {
List<Map<String, String>> arrayListCountryDetails = new ArrayList<>();
GetCountryList getCountryList = new GetCountryList();
arrayListCountryDetails = getCountryList.CallWebServiceForCountryDetails(this);
return arrayListCountryDetails;
}
@Override
protected void onPostExecute(List<Map<String, String>> arrayListCountryDetails) {
CountryDetailsAdapter countryDetailsAdapter = new CountryDetailsAdapter(SignUpActivity.this, arrayListCountryDetails);
spinnerCountryName.setAdapter(countryDetailsAdapter);
}
@Override
protected void onPreExecute() {}
@Override
protected void onProgressUpdate(Void... values) {}
}
task.execute();
}
同时从GetCountryList
删除任何 UI 调用,因为这将在“后台”运行
加载数据时传递 Spinner 对象并在加载完成后设置适配器
public class GetCountryList {
ProgressDialog dialog;
APIService mAPIService;
public void CallWebServiceForCountryDetails(final Context context,final Spinner spinnerCountryName) {
dialog = new ProgressDialog(context);
dialog.setMessage("Please wait...");
dialog.setCancelable(false);
dialog.show();
final ArrayList<HashMap<String, String>> arrayListCountryDetails = new ArrayList<>();
mAPIService = ApiUtils.getAPIService();
mAPIService.getCountryDetails().enqueue(new Callback<CountryDetailsResponseModel>() {
@Override
public void onResponse(Call<CountryDetailsResponseModel> call, Response<CountryDetailsResponseModel> response) {
if (response.isSuccessful()) {
HashMap<String, String> cntDetails = new HashMap<>();
cntDetails.put("airLineID", "0");
cntDetails.put("airLineName", "Select Airline");
arrayListCountryDetails.add(cntDetails);
// Get response
try {
if (response.body().getStatus() == 200 && response.body().getMessage().equalsIgnoreCase("success")) {
for (int count = 0; count < response.body().getCountry().size(); count++) {
cntDetails = new HashMap<>();
String countryID = response.body().getCountry().get(count).getCountryId();
String countryName = response.body().getCountry().get(count).getCountryName();
cntDetails.put("countryID", countryID);
cntDetails.put("countryName", countryName);
arrayListCountryDetails.add(cntDetails);
}
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
//set Adapter
CountryDetailsAdapter countryDetailsAdapter = new CountryDetailsAdapter(context, arrayListCountryDetails);
spinnerCountryName.setAdapter(countryDetailsAdapter);
} else {
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
}
} catch (Exception e) {
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
}
}
}
@Override
public void onFailure(Call<AirLineDetailsResponseModel> call, Throwable t) {
// do UI work here
if (dialog.isShowing()) {
dialog.dismiss();
}
}
});
}
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