Question

我在数据库中有一条记录，必须在树表视图中。这是填充方法：

 private void updateGoods(){
        goodsPane.setCenter(goodTreeTableView);
        List<Good> goodAndFoldersList;
       try {
           goodAndFoldersList = goodsService.getGoods();//database query
       }catch (SQLException e){
           goodAndFoldersList = new ArrayList<>();
           log.log(Level.ERROR, e.getMessage());
       }
           List<Good> goods = new ArrayList<Good>();//list for roots
           List<Good> roots = new ArrayList<Good>();//list for goods themselves
           for (Good good : goodAndFoldersList) {
               if (good.isIs_folder()) {
                   roots.add(good);
               } else {
                   goods.add(good);
               }
           }
           TreeItem<Good> rootItem = new TreeItem<>();//the main root
           for (Good root : roots) {
               Long folderId = root.getId();
               TreeItem<Good> rootTreeItem = new TreeItem<>(root);
               for (Good good : goods) {//looking for goods for each folder
                   if (good.getFolderId() == folderId) {
                       TreeItem<Good> goodTreeItem = new TreeItem<>(good);
                       rootTreeItem.getChildren().add(goodTreeItem);
                   }
               }
               rootItem.getChildren().add(rootTreeItem);//adding every folder to the main root
           }        
           goodTreeTableView = new TreeTableView<>(rootItem);
    }

在此方法之后，用户在treeTableView中看不到任何内容。也许有必要定义单元格内容，但这个代码放在goodTreeTableView = new TreeTableView<>(rootItem);之前会丢弃NullPointerException：

        goodName.setCellValueFactory((TreeTableColumn.CellDataFeatures<Good, String> param) ->
                new ReadOnlyStringWrapper(param.getValue().getValue().getName()));
        folderId.setCellValueFactory((TreeTableColumn.CellDataFeatures<Good, Number> param) ->
                new ReadOnlyLongWrapper(param.getValue().getValue().getFolderId()));
        is_folder.setCellValueFactory((TreeTableColumn.CellDataFeatures<Good, Boolean> param) ->
                new ReadOnlyBooleanWrapper(param.getValue().getValue().isIs_folder()));

我想这就是我的问题的原因，但为什么这会导致NPE我无法理解。

UPD：如果我添加设置单元格值工厂，我会得到以下堆栈跟踪：

javafx.fxml.LoadException: 
/D:/javaEdi/linkserver/ediagent/target/classes/com/ediagent/edi/gui/Main.fxml

    at javafx.fxml.FXMLLoader.constructLoadException(FXMLLoader.java:2595)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2565)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2435)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:2403)
    at com.ediagent.edi.gui.Main.initRootLayout(Main.java:44)
    at com.ediagent.edi.gui.Main.start(Main.java:27)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$153(LauncherImpl.java:821)
    at com.sun.javafx.application.LauncherImpl$$Lambda$51/1546859350.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$166(PlatformImpl.java:323)
    at com.sun.javafx.application.PlatformImpl$$Lambda$44/1712669532.run(Unknown Source)
    at com.sun.javafx.application.PlatformImpl.lambda$null$164(PlatformImpl.java:292)
    at com.sun.javafx.application.PlatformImpl$$Lambda$47/157858792.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$165(PlatformImpl.java:291)
    at com.sun.javafx.application.PlatformImpl$$Lambda$46/1225373914.run(Unknown Source)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$141(WinApplication.java:102)
    at com.sun.glass.ui.win.WinApplication$$Lambda$37/152005629.run(Unknown Source)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
    at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:2560)
    ... 18 more
Caused by: java.lang.NullPointerException
    at com.ediagent.edi.gui.MainController.updateGoods(MainController.java:309)
    at com.ediagent.edi.gui.MainController.initialize(MainController.java:328)
    ... 28 more

** UPD：** rootItem：

Answer 1

您正在通过重新初始化将数据添加到FXML上的GUI元素。避免重新初始化FXML元素。

您可以将updateGoods()的签名更改为：

public TreeItem<Good> updateGoods() {
...
}

并在MainController中使用它来设置项目

goodTreeTableView.setRoot(updateGoods());

最好还可以从updateGoods()返回数据（List），而不是返回TreeItem。在Controller中创建它并将其设置为goodTreeTableView的根目录。

如何正确填充treeTableView

1 个答案: