带有cellfactory的javafx组合框不显示所选项目
我有一个小的概念验证应用程序,它包含6个带有cellfactory的javafx组合框不显示所选项目,java,javafx,combobox,observablelist,Java,Javafx,Combobox,Observablelist,我有一个小的概念验证应用程序,它包含6个标签一个组合框和一个按钮,所有这些都是使用SceneBuilder创建的 通过单击按钮,应用程序进行Json api调用,以返回国家列表及其相关详细信息(apla2code、apla3code、名称等)。我创建了一个CountryDetails对象,其中包含3个String元素。我使用它返回一个CountryDetails数组,然后将其加载到ObserbavleList数组中。然后,我将其应用于组合框,每次在组合框中选择一个项目时,我都会将CountryD
标签
一个组合框
和一个按钮
,所有这些都是使用SceneBuilder创建的
通过单击按钮
,应用程序进行Json api调用,以返回国家列表及其相关详细信息(apla2code、apla3code、名称等)。我创建了一个CountryDetails
对象,其中包含3个String
元素。我使用它返回一个CountryDetails
数组,然后将其加载到ObserbavleList
数组中。然后,我将其应用于组合框,每次在组合框中选择一个项目时,我都会将CountryDetails元素加载到3个标签中。所有这些都很好(尽管可能有更好的方法)
我遇到的问题是,组合框
没有显示所选项目,我不知道如何更正。下图显示了问题所在
进行api调用的代码如下所示:
import com.google.gson.Gson;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class GetCountries {
public CountryDetails[] getDetails() {
String inputLine = "";
StringBuilder jsonString = new StringBuilder();
HttpURLConnection urlConnection;
try {
URL urlObject = new URL("https://restcountries.eu/rest/v2/all");
urlConnection = (HttpURLConnection) urlObject.openConnection();
urlConnection.setRequestMethod("GET");
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
while ((inputLine = bufferedReader.readLine()) != null) {
jsonString.append(inputLine);
}
urlConnection.getInputStream().close();
} catch(IOException ioe) {
System.out.println(ioe.getMessage());
}
Countries[] countries = new Gson().fromJson(jsonString.toString(), Countries[].class);
CountryDetails[] countryDetails = new CountryDetails[countries.length];
for(int i = 0; i < countries.length; i++){
countryDetails[i] = new CountryDetails(
countries[i].getAlpha2Code(),
countries[i].getAlpha3Code(),
countries[i].getName()
);
}
return countryDetails;
}
}
public class CountryDetails {
private String alpha2Code;
private String alpha3Code;
private String name;
public CountryDetails(String strAlpha2Code, String strAlpha3Code, String strName) {
this.alpha2Code = strAlpha2Code;
this.alpha3Code = strAlpha3Code;
this.name = strName;
}
public String getAlpha2Code() { return alpha2Code; }
public void setAlpha2Code(String alpha2Code) { this.alpha2Code = alpha2Code; }
public String getAlpha3Code() { return alpha3Code; }
public void setAlpha3Code(String alpha3Code) { this.alpha3Code = alpha3Code; }
public String getName() { return name; }
public void setName(String name) {this.name = name; }
}
cbCountryList.setCellFactory(new Callback<ListView<CountryDetails>, ListCell<CountryDetails>>() {
@Override public ListCell<CountryDetails> call(ListView<CountryDetails> p) {
return new ListCell<CountryDetails>() {
@Override
protected void updateItem(CountryDetails item, boolean empty) {
super.updateItem(item, empty);
if (empty || (item == null) || (item.getName() == null)) {
setText(null);
} else {
setText(item.getName());
}
}
};
}
});
public void comboAction(ActionEvent event) {
lblAlpha2Code.setText(cbCountryList.getValue().getAlpha2Code());
lblAlpha3Code.setText(cbCountryList.getValue().getAlpha3Code());
lblCountryName.setText(cbCountryList.getValue().getName());
}
加载可观察列表的代码如下所示:
GetCountries countries = new GetCountries();
CountryDetails[] countryDetails = countries.getDetails();
for (CountryDetails countryDetail : countryDetails) {
countriesObservableList.add(new CountryDetails(
countryDetail.getAlpha2Code(),
countryDetail.getAlpha3Code(),
countryDetail.getName())
);
}
加载组合框并在标签中显示元素的代码如下:
import com.google.gson.Gson;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
public class GetCountries {
public CountryDetails[] getDetails() {
String inputLine = "";
StringBuilder jsonString = new StringBuilder();
HttpURLConnection urlConnection;
try {
URL urlObject = new URL("https://restcountries.eu/rest/v2/all");
urlConnection = (HttpURLConnection) urlObject.openConnection();
urlConnection.setRequestMethod("GET");
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
while ((inputLine = bufferedReader.readLine()) != null) {
jsonString.append(inputLine);
}
urlConnection.getInputStream().close();
} catch(IOException ioe) {
System.out.println(ioe.getMessage());
}
Countries[] countries = new Gson().fromJson(jsonString.toString(), Countries[].class);
CountryDetails[] countryDetails = new CountryDetails[countries.length];
for(int i = 0; i < countries.length; i++){
countryDetails[i] = new CountryDetails(
countries[i].getAlpha2Code(),
countries[i].getAlpha3Code(),
countries[i].getName()
);
}
return countryDetails;
}
}
public class CountryDetails {
private String alpha2Code;
private String alpha3Code;
private String name;
public CountryDetails(String strAlpha2Code, String strAlpha3Code, String strName) {
this.alpha2Code = strAlpha2Code;
this.alpha3Code = strAlpha3Code;
this.name = strName;
}
public String getAlpha2Code() { return alpha2Code; }
public void setAlpha2Code(String alpha2Code) { this.alpha2Code = alpha2Code; }
public String getAlpha3Code() { return alpha3Code; }
public void setAlpha3Code(String alpha3Code) { this.alpha3Code = alpha3Code; }
public String getName() { return name; }
public void setName(String name) {this.name = name; }
}
cbCountryList.setCellFactory(new Callback<ListView<CountryDetails>, ListCell<CountryDetails>>() {
@Override public ListCell<CountryDetails> call(ListView<CountryDetails> p) {
return new ListCell<CountryDetails>() {
@Override
protected void updateItem(CountryDetails item, boolean empty) {
super.updateItem(item, empty);
if (empty || (item == null) || (item.getName() == null)) {
setText(null);
} else {
setText(item.getName());
}
}
};
}
});
public void comboAction(ActionEvent event) {
lblAlpha2Code.setText(cbCountryList.getValue().getAlpha2Code());
lblAlpha3Code.setText(cbCountryList.getValue().getAlpha3Code());
lblCountryName.setText(cbCountryList.getValue().getName());
}
cbCountryList.setCellFactory(新回调(){
@覆盖公共ListCell调用(ListView p){
返回新的ListCell(){
@凌驾
受保护的void updateItem(CountryDetails项,布尔值为空){
super.updateItem(项,空);
if(空| |(item==null)| |(item.getName()==null)){
setText(空);
}否则{
setText(item.getName());
}
}
};
}
});
公共无效组合动作(ActionEvent事件){
lblAlpha2Code.setText(cbCountryList.getValue().getAlpha2Code());
lblAlpha3Code.setText(cbCountryList.getValue().getAlpha3Code());
lblconyname.setText(cbCountryList.getValue().getName());
}
以下是该应用程序的图像:
我遇到的问题是,组合框没有显示所选项目,我不知道如何更正
您需要为cbCountryList
设置一个
cbCountryList.setConverter(new StringConverter<CountryDetails>() {
@Override
public String toString(CountryDetails object) {
return object.getName();
}
@Override
public CountryDetails fromString(String string) {
return null;
}
});
用于异步获取您的国家/地区
Task<CountryDetails[]> fetchCountryTask = new Task<CountryDetails[]>() {
@Override
protected CountryDetails[] call() throws Exception {
return GetCountries.getDetails();
}
};
fetchButton.setOnAction(event -> new Thread(fetchCountryTask).start());
fetchCountryTask.setOnRunning(event -> cbCountryList.setDisable(true));
fetchCountryTask.setOnSucceeded(e -> {
cbCountryList.getItems().addAll(fetchCountryTask.getValue());
cbCountryList.setDisable(false);
});
Task fetchCountryTask=新任务(){
@凌驾
受保护的CountryDetails[]调用()引发异常{
返回GetCountries.getDetails();
}
};
setOnAction(事件->新线程(fetchCountryTask.start());
fetchCountryTask.setOnRunning(事件->cbCountryList.setDisable(true));
fetchCountryTask.setOnSucceeded(e->{
cbCountryList.getItems().addAll(fetchCountryTask.getValue());
cbCountryList.setDisable(false);
});
将设置为自定义单元工厂返回的实例。Sekhar Rai:谢谢。StringConverter
起到了很好的作用。至于异步调用和缓存,这只是一个概念证明,最终将成为大型应用程序配置向导的一部分。该列表仅在向导加载时生成一次,不会再次调用。但是,对于需要更频繁地在同一会话中访问类似返回Json数据的应用程序的其他部分来说,这无疑是有用的。