Java SwingWorker done（）方法使用get（）抛出nullpointerexception

我编写了一个swing worker，负责计算一些文本统计信息，然后用结果更新EDT中的GUI元素。 经过一些实验，我发现您应该只在

done（）

方法中操作GUI，而不是在

doInBackground（）中操作。为了实现这一点，我将worker重新建模为具有返回值
String[]
，我应该能够使用
get（）
获取该值。
除了一些
publish（）
方法之外，您可能会发现一些来自直接操作GUI的
doInBackground（）
方法的错误调用，如果您认为我的问题可能是由此引起的，请告诉我

package my.worker;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.TreeSet;
import java.util.concurrent.ExecutionException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JComboBox;
import javax.swing.JLabel;
import javax.swing.JProgressBar;
import javax.swing.SwingWorker;
import my.tools.CountKeywords;
import my.tools.FilterStopwords;
import my.tools.KeywordSuggestion;
import my.tools.RelevanceRanking;

public class ProcessDatabaseWorker extends SwingWorker<String[], String> {

    private final JLabel debugJLabel;
    private final JLabel infoJLabel;
    private final JLabel warnJLabel;
    private final JLabel errorJLabel;
    private final JLabel infoboxJLabel;
    private final String databaseString;
    private final JProgressBar jProgressBar;
    private final JComboBox keywordJComboBox;
    private int percent;
    private int index;

public ProcessDatabaseWorker(JProgressBar jProgressBar, String databaseString,
            JLabel debugJLabel, JLabel errorJLabel, JLabel warnJLabel,
            JLabel infoJLabel, JLabel infoboxJLabel,
            JComboBox keywordJComboBox) {
        this.percent = 1;
        this.jProgressBar = jProgressBar;
        this.databaseString = databaseString;
        this.debugJLabel = debugJLabel;
        this.errorJLabel = errorJLabel;
        this.infoJLabel = infoJLabel;
        this.warnJLabel = warnJLabel;
        this.infoboxJLabel = infoboxJLabel;
        this.keywordJComboBox = keywordJComboBox;
    }

    @Override
    protected String[] doInBackground() throws Exception {
        FilterStopwords fs = new FilterStopwords();
        CountKeywords ck = new CountKeywords();
        RelevanceRanking rr = new RelevanceRanking();
        HashMap<String, Integer> nKeywords = new HashMap();
        Map<String, TreeSet<Map.Entry<String, Double>>> keywordsPerDocument = new HashMap();
        String replace = databaseString.toLowerCase();
        String splitter = ("\\n");
        String[] documentLines = replace.split(splitter);
        int N = documentLines.length;
        publish("Stopworte werden gefiltert...", "10");
        String[] completeFilteredText = fs.filterStopwords(replace);
        publish("Keywords werden gezählt...", "20");
        HashMap<String, Integer> completeKeywords = ck.countKeywords(completeFilteredText);
        index = 0;
        percent = 1;
        final double oneLinePercent = N / 100;
        final double oneKeywordPercent = completeKeywords.size() / 100;
        completeKeywords.forEach((String key, Integer value) -> {
            int n = 0;
            key = String.valueOf(key).trim();
            for (String line : documentLines) {
                String[] lineWords = line.split(" ");
                for (String word : lineWords) {
                    word = word.trim();
                    if (word.equals(key)) {
                        n++;
                        nKeywords.put(key, n);
                    }
                }
            }
            index++;
            if (index == oneKeywordPercent) {
                percent++;
                publish("Zählung...", String.valueOf(percent));
                index = 0;
            }
        });
        publish("Keywords werden geranked...", "40");
        index = 0;
        percent = 1;
        for (String documentLine : documentLines) {
            TreeSet<Map.Entry<String, Double>> rankedKeywords;
            String[] lineFilteredWords = fs.filterStopwords(documentLine);
            HashMap<String, Integer> keywords = ck.countKeywords(lineFilteredWords);
            rankedKeywords = rr.rankKeywords(keywords, lineFilteredWords, N, nKeywords);
            keywordsPerDocument.put(documentLine, rankedKeywords);
            index++;
            if (index == oneLinePercent) {
                percent++;
                publish("Ranking...", String.valueOf(percent));
                index = 0;
            }
        }
        publish("Keyword-Vorschläge werden generiert...", "70");
        KeywordSuggestion ks = new KeywordSuggestion();
        TreeSet<Map.Entry<String, Double>> keywordSuggestionsTree = ks.keywordSuggestion(keywordsPerDocument);
        String[] keywordSuggestionsArray = new String[keywordSuggestionsTree.size()];
        index = 0;
        int index2 = 0;
        double onePercent = keywordSuggestionsTree.size() / 100;
        percent = 1;
        publish("Keyword-Vorschläge werden generiert...", "75");
        for (Map.Entry<String, Double> entry : keywordSuggestionsTree) {
            double round = round(entry.getValue(), 2);
            keywordSuggestionsArray[index2] = round + " - " + entry.getKey();
            index2++;
            index++;
            if (index == onePercent) {
                percent++;
                publish("Keywords...", String.valueOf(percent));
                index = 0;
            }
        }
        keywordJComboBox.removeAllItems();
        for (String entry : keywordSuggestionsArray) {
            publish("Keyword-Vorschläge werden befüllt...", "80");
        }

有关更多信息，请参阅完整的跟踪：

Apr 14, 2016 10:40:06 AM my.worker.ProcessDatabaseWorker done
SCHWERWIEGEND: null
java.util.concurrent.ExecutionException: java.lang.NullPointerException
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    at javax.swing.SwingWorker.get(SwingWorker.java:602)
    at my.worker.ProcessDatabaseWorker.done(ProcessDatabaseWorker.java:197)
    at javax.swing.SwingWorker$5.run(SwingWorker.java:737)
    at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:832)
    at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:112)
    at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:842)
    at javax.swing.Timer.fireActionPerformed(Timer.java:313)
    at javax.swing.Timer$DoPostEvent.run(Timer.java:245)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Caused by: java.lang.NullPointerException
    at my.logfileanalyzer.LogFileAnalyzerGUI.keywordJComboBoxItemStateChanged(LogFileAnalyzerGUI.java:830)
    at my.logfileanalyzer.LogFileAnalyzerGUI.access$2400(LogFileAnalyzerGUI.java:48)
    at my.logfileanalyzer.LogFileAnalyzerGUI$15.itemStateChanged(LogFileAnalyzerGUI.java:329)
    at javax.swing.JComboBox.fireItemStateChanged(JComboBox.java:1223)
    at javax.swing.JComboBox.selectedItemChanged(JComboBox.java:1271)
    at javax.swing.JComboBox.contentsChanged(JComboBox.java:1330)
    at javax.swing.JComboBox.intervalRemoved(JComboBox.java:1352)
    at javax.swing.AbstractListModel.fireIntervalRemoved(AbstractListModel.java:179)
    at javax.swing.DefaultComboBoxModel.removeAllElements(DefaultComboBoxModel.java:174)
    at javax.swing.JComboBox.removeAllItems(JComboBox.java:771)
    at my.worker.ProcessDatabaseWorker.doInBackground(ProcessDatabaseWorker.java:165)
    at my.worker.ProcessDatabaseWorker.doInBackground(ProcessDatabaseWorker.java:43)
    at javax.swing.SwingWorker$1.call(SwingWorker.java:295)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at javax.swing.SwingWorker.run(SwingWorker.java:334)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

现在，对于我的问题：我使用的工作程序的哪一部分不是正确的，或者我的程序逻辑哪里出错了？正如您所看到的，我对使用swing Worker和线程进行编程非常陌生，所以我相信对于由经验不足导致的简单错误，有一个简单的解决方案

此外，如果需要我的程序的任何其他部分，请让我知道，以便更好地了解正在发生的事情

编辑：错误就在用户Moh-Aw描述的地方-编辑了我的代码，如下所示：

private void keywordJComboBoxItemStateChanged(java.awt.event.ItemEvent evt) {                                                  
        if (keywordJComboBox.getItemCount() != 0){
            if (!((String) keywordJComboBox.getSelectedItem()).equals("")) {
                String selected = (String) keywordJComboBox.getSelectedItem();
                String[] blubb = selected.split(" ");
                searchJTextField.setText(blubb[2]);
            }
        }
    }   

编辑：关于可能的重复-我很确定这篇文章是正确的。老实说，我认为这是swing workers的一个错误实现，而不是像实际那样简单-因此，这篇文章也可以关闭^^ ^
问题是您的
LogFileAnalyzerGUI
类的第830行。
keywordJComboBox
的
itemStateChanged（）
方法导致
NullPointerException

此方法由位于
关键字jcombobox.removeAllItems（）

通过删除所有项目，
ItemState
将更改为取消选择

方法
itemStateChanged（）
再次运行，但组合框中没有更多的项，因此导致NPE。
问题是
LogFileAnalyzerGUI
类的第830行。
keywordJComboBox
的
itemStateChanged（）
方法导致
NullPointerException

此方法由位于
关键字jcombobox.removeAllItems（）

通过删除所有项目，
ItemState
将更改为取消选择

方法
itemStateChanged（）
再次运行，但组合框中没有更多的项，因此导致NPE。
是否在组合框的itemStateChanged上启动SwingWorker？如果是，请发布该部分。您可以再次删除编辑，因为它没有帮助。而是发布
LogFileAnalyzerGUI
类的方法
KeywordJComboxItemStateChanged（）
。是否在组合框的itemStateChanged上启动SwingWorker？如果是，请发布该部分。您可以再次删除编辑，因为它没有帮助。而是发布
LogFileAnalyzerGUI
类的方法
KeywordJComboxItemStateChanged（）
。
Apr 14, 2016 10:40:06 AM my.worker.ProcessDatabaseWorker done
SCHWERWIEGEND: null
java.util.concurrent.ExecutionException: java.lang.NullPointerException
    at java.util.concurrent.FutureTask.report(FutureTask.java:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:192)
    at javax.swing.SwingWorker.get(SwingWorker.java:602)
    at my.worker.ProcessDatabaseWorker.done(ProcessDatabaseWorker.java:197)
    at javax.swing.SwingWorker$5.run(SwingWorker.java:737)
    at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:832)
    at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:112)
    at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:842)
    at javax.swing.Timer.fireActionPerformed(Timer.java:313)
    at javax.swing.Timer$DoPostEvent.run(Timer.java:245)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:756)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:726)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)
Caused by: java.lang.NullPointerException
    at my.logfileanalyzer.LogFileAnalyzerGUI.keywordJComboBoxItemStateChanged(LogFileAnalyzerGUI.java:830)
    at my.logfileanalyzer.LogFileAnalyzerGUI.access$2400(LogFileAnalyzerGUI.java:48)
    at my.logfileanalyzer.LogFileAnalyzerGUI$15.itemStateChanged(LogFileAnalyzerGUI.java:329)
    at javax.swing.JComboBox.fireItemStateChanged(JComboBox.java:1223)
    at javax.swing.JComboBox.selectedItemChanged(JComboBox.java:1271)
    at javax.swing.JComboBox.contentsChanged(JComboBox.java:1330)
    at javax.swing.JComboBox.intervalRemoved(JComboBox.java:1352)
    at javax.swing.AbstractListModel.fireIntervalRemoved(AbstractListModel.java:179)
    at javax.swing.DefaultComboBoxModel.removeAllElements(DefaultComboBoxModel.java:174)
    at javax.swing.JComboBox.removeAllItems(JComboBox.java:771)
    at my.worker.ProcessDatabaseWorker.doInBackground(ProcessDatabaseWorker.java:165)
    at my.worker.ProcessDatabaseWorker.doInBackground(ProcessDatabaseWorker.java:43)
    at javax.swing.SwingWorker$1.call(SwingWorker.java:295)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at javax.swing.SwingWorker.run(SwingWorker.java:334)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)

private void keywordJComboBoxItemStateChanged(java.awt.event.ItemEvent evt) {                                                  
        if (keywordJComboBox.getItemCount() != 0){
            if (!((String) keywordJComboBox.getSelectedItem()).equals("")) {
                String selected = (String) keywordJComboBox.getSelectedItem();
                String[] blubb = selected.split(" ");
                searchJTextField.setText(blubb[2]);
            }
        }
    }