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我對Primefaces數據表有問題，特別是對選擇對象。Primefaces數據表選擇對象
在我的下面的代碼中，我總是爲變量「Selected Question」得到Null，這個變量綁定到Datatable with Selection。
如隨後在JSF：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:p="http://primefaces.org/ui"
xmlns:ui="http://java.sun.com/jsf/facelets">
<ui:composition template="mainTemplate.xhtml">
<ui:define name="contentTitle">Your Questions</ui:define>
<ui:define name="content">
<h:form id="formAllQuestion">
<p:growl id="allQuestionGrowl" showDetail="true"/>
<p:dataTable id="allQuestionsTable" var="question" value="#{allQuestionBean.allQuestionDataHelper}" paginator="true" rows="10"
selection="#{allQuestionBean.selectedQuestion}" selectionMode="single">
<p:ajax event="rowSelect" listener="#{allQuestionBean.onRowSelect}" update=":formAllQuestion:AnswerToQuestionDialogTable :formAllQuestion:allQuestionGrowl"
oncomplete="questDialog.show()"/>
<p:ajax event="rowUnselect" listener="#{allQuestionBean.onRowUnselect}" update=":formAllQuestion:allQuestionGrowl"/>
<f:facet name="header">Select a Row to display your Question Details</f:facet>
<p:column headerText="QuestionID">
#{question.questionId}
</p:column>
<p:column headerText="Question Name">
#{question.questionName}
</p:column>
<p:column headerText="Question Description">
#{question.questionText}
</p:column>
<p:column headerText="Question Short Description">
#{question.questionShortText}
</p:column>
<p:column headerText="Author">
#{question.professor.profSurename} #{question.professor.profName}
</p:column>
</p:dataTable>
<p:dialog header="Question Details" widgetVar="questionDialog" resizable="true" id="questDialog"
showEffect="fade" hideEffect="fade" modal="true">
<p:dataTable id="AnswerToQuestionDialogTable" var="answer" value="#{allQuestionBean.answers}">
<f:facet name="header">
Hier kommt der QR_Code rein!
#{allQuestionBean.selectedQuestion.questionId} - #{allQuestionBean.selectedQuestion.questionName}
</f:facet>
<p:column headerText="Answer">
<h:outputText value="#{answer.answerText}"/>
</p:column>
<p:column headerText="Counts For this Answer">
<h:outputText value="Bis jetz noch nix!"/>
</p:column>
</p:dataTable>
</p:dialog>
</h:form>
</ui:define>
</ui:composition>
</html>
和相關聯的Bean類（AllQuestionBean.class）：
@ManagedBean(name = "allQuestionBean")
@ViewScoped
public class AllQuestionBean implements Serializable {
private static final long serialVersionUID = 7038894302985973905L;
@ManagedProperty(value = "#{questionDAO}")
private QuestionDAO questionDAO;
@ManagedProperty(value = "#{profSession.professor}")
private Professor professor;
@ManagedProperty(value = "#{answerDAO}")
private AnswerDAO answerDAO;
@ManagedProperty(value = "#{answeredDAO}")
private AnsweredDAO answeredDAO;
private List<Question> questions;
private Question selectedQuestion;
private List<Answer> answers;
private AllQuestionDataHelper allQuestionDataHelper;
public AllQuestionBean(){
System.out.println("Starting Bean: "+this.getClass().getName());
}
@PostConstruct
public void initVariables(){
questions = questionDAO.readByProfessor(professor);
}
public void onRowSelect(SelectEvent event) {
FacesMessage msg = new FacesMessage("Question Selected", selectedQuestion.getQuestionId()+" -- "+selectedQuestion.getQuestionName());
FacesContext.getCurrentInstance().addMessage(null, msg);
}
public void onRowUnselect(UnselectEvent event) {
FacesMessage msg = new FacesMessage("Question Selected", selectedQuestion.getQuestionId()+" -- "+selectedQuestion.getQuestionName());
FacesContext.getCurrentInstance().addMessage(null, msg);
}
//---GETTER and SETTER
public AllQuestionDataHelper getAllQuestionDataHelper() {
allQuestionDataHelper = new AllQuestionDataHelper(questions);
return allQuestionDataHelper;
}
public void setAllQuestionDataHelper(AllQuestionDataHelper allQuestionDataHelper) {
this.allQuestionDataHelper = allQuestionDataHelper;
}
public QuestionDAO getQuestionDAO() {
return questionDAO;
}
public void setQuestionDAO(QuestionDAO questionDAO) {
this.questionDAO = questionDAO;
}
public Professor getProfessor() {
return professor;
}
public void setProfessor(Professor professor) {
this.professor = professor;
}
public AnswerDAO getAnswerDAO() {
return answerDAO;
}
public void setAnswerDAO(AnswerDAO answerDAO) {
this.answerDAO = answerDAO;
}
public AnsweredDAO getAnsweredDAO() {
return answeredDAO;
}
public void setAnsweredDAO(AnsweredDAO answeredDAO) {
this.answeredDAO = answeredDAO;
}
public List<Question> getQuestions() {
return questions;
}
public void setQuestions(List<Question> questions) {
this.questions = questions;
}
public Question getSelectedQuestion() {
System.out.println("getSelectedQuestion");
return selectedQuestion;
}
public void setSelectedQuestion(Question selectedQuestion) {
System.out.println("Set selected Question: "+selectedQuestion);
this.selectedQuestion = selectedQuestion;
}
public List<Answer> getAnswers() {
answers = answerDAO.getAllAnswersForQuestion(selectedQuestion);
return answers;
}
public void setAnswers(List<Answer> answers) {
this.answers = answers;
}
}
數據型號名稱：
public class AllQuestionDataHelper extends ListDataModel<Question> implements SelectableDataModel<Question> {
public AllQuestionDataHelper() {
}
public AllQuestionDataHelper(List<Question> list) {
super(list);
}
@Override
public Object getRowKey(Question question) {
if(!(question == null)){
System.out.println("Your Questions --> Getting RowKey");
System.out.println("RowKey: "+question);
System.out.println("RowKey: "+question.getQuestionId());
}else{
System.out.println("Warning Row Key is null");
}
return question.getQuestionId();
}
@Override
public Question getRowData(String rowKey) {
System.out.println("Your Questions --> Getting RowData");
System.out.println("RowData: "+rowKey);
List<Question> questionList = (List<Question>) getWrappedData();
for(Question q : questionList){
if(rowKey.equals(q.getQuestionId())){
System.out.println("Returning "+q.getQuestionId());
return q;
}
}
return null;
}
}
我調試幾個運行並提到AllQuestionBean.class中的變量「selectedQuestion」從不設置。會說，「onRowSelect」中的事件變量包含一個NULL對象。如您所見，* .xhtml中有兩個Datatables。第一個將正常加載，沒有問題。 Bean的onClick-Method應該用第二個數據表啓動一個對話框，但是會用一個空指針退出。
對於DataTable中我也跟着教程在Primefaces（http://www.primefaces.org/showcase-labs/ui/datatableRowSelectionInstant.jsf）
您是否需要爲您選擇的數據表使用rowKey？ – JamesB
我以爲rowKey來自數據模型。一會兒，我會用模型來源更新這個問題。 – Chris
好的，我用Nullpointer解決了這個問題。它是DataModel類中的getRowData（）方法。我試圖等於一個整數字符串，發生在這個時間:)好吧，表現在不會拋出一個Nullpointer，但面臨另一個問題。我只能在桌面上點擊一次。每隔一次點擊對錶格沒有影響。有沒有範圍或與Ajax的問題？ – Chris