JavaFX TreeView：setGraphic（）用于不同级别的treeItem [英] JavaFX TreeView: setGraphic() for different levels of treeItem

问题描述

我正在创建一个TreeView，它应该为不同级别的树结构提供不同的图形。这是一个三级结构，其中隐藏了根。

可扩展节点的图形：
http://i.imgur.com/wv00CEi.png

叶子节点：$ b​​
$ b

只是一个hBox中的标签。

这是我迄今为止所尝试的，但是我得到一个nullPointerException异常，基本上说getTreeView为null：

CustomTreeCellFactory

 
  public final class CustomTreeCellFactory扩展TreeCell< String> {
 private TextField textField; 
私人HBox hBox; 
 
 public CustomTreeCellFactory（）{
 super（）; 
 if（getTreeView（）== null）{
 System.out.println（Her er problem）; 
} 
 if（getTreeView（）。getTreeItemLevel（getTreeItem（））== 1）{
 try {
 hBox =（HBox）FXMLLoader.load（getClass（）。getResource （ /Views/TreCell.fxml））; 
} catch（IOException e）{
 System.out.println（This did not work）; 
 e.printStackTrace（）; 
 
 
 else if（getTreeView（）。getTreeItemLevel（getTreeItem（））== 2）{
 try {
 hBox =（HBox）FXMLLoader.load （的getClass（）的getResource（ /查看/ TreCellLowestLevel.fxml）。）; 
} catch（IOException e）{
 System.out.println（This did not work）; 
 e.printStackTrace（）; 
} 
} 
 
 
} 
  

设置Cell Factory的代码片段

  TreeView< String> tree =（TreeView）parent.getChildren（）。get（0）; 
 tree.setRoot（root）; 
 tree.setShowRoot（false）; 
 tree.setEditable（true）; 
 tree.setCellFactory（new Callback< TreeView< String>，TreeCell< String>>（）{
 @Override 
 public TreeCell< String> call（TreeView< String> param） b $ b返回新的CustomTreeCellFactory（）; 
} 
}）; 
  

解决方案

我发现问题所在。

在设置TreeView时，我试图做的工作需要在更新方法中完成。

这里是解决了这个问题的代码：

$ $ $ $ $ $ $ $ $ $ $ public $ {
$ public $ {
$ {
hBox =（HBox）FXMLLoader.load（getClass（）。getResource（/ Views / TreCell.fxml））;
} catch（IOException e）{
System.out.println（This did not work）;
e.printStackTrace（）;

try {
hBoxLeaf =（HBox）FXMLLoader.load（getClass（）。getResource（/ Views / TreCellLowestLevel.fxml））;
} catch（IOException e）{
System.out.println（This did not work）;
e.printStackTrace（）;
}

}

更新方法

  @Override 
 public void updateItem（String item，boolean empty）{
 super.updateItem （项目，空）; 
 
 if（item！= null）{
 if（getTreeView（）。getTreeItemLevel（getTreeItem（））== 1）{$ b $ setGraphic（this.hBox）; 
} else if（getTreeView（）。getTreeItemLevel（getTreeItem（））== 2）{
 setGraphic（this.hBoxLeaf）; 
} 
} else {
 setGraphic（null）; 
} 
} 
  

I'm creating a TreeView that should have different graphics for different levels of the treestructure. It is a 3-level structure, where the root is hidden.

The graphic for expandable nodes: http://i.imgur.com/wv00CEi.png

The graphic for leaf nodes:

Just a label in an hBox.

This is what I have tried so far, but I get a nullPointerException basically saying getTreeView is null:

CustomTreeCellFactory

public final class CustomTreeCellFactory extends TreeCell<String>{
private TextField textField;
private HBox hBox;

public CustomTreeCellFactory(){
    super();
    if (getTreeView()==null){
        System.out.println("Her er problem");
    }
    if (getTreeView().getTreeItemLevel(getTreeItem())==1){
        try {
            hBox = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCell.fxml"));
        } catch (IOException e) {
            System.out.println("This didn't work");
            e.printStackTrace();
        }
    }
    else if (getTreeView().getTreeItemLevel(getTreeItem())==2){
        try {
            hBox = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCellLowestLevel.fxml"));
        } catch (IOException e) {
            System.out.println("This didn't work");
            e.printStackTrace();
        }
    }


}

Code snippet from where I set the Cell Factory

TreeView<String> tree = (TreeView) parent.getChildren().get(0);
    tree.setRoot(root);
    tree.setShowRoot(false);
    tree.setEditable(true);
    tree.setCellFactory(new Callback<TreeView<String>, TreeCell<String>>() {
        @Override
        public TreeCell<String> call(TreeView<String> param) {
            return new CustomTreeCellFactory();
        }
    });

解决方案

I found out what the problem was.

What I tried to do needed to be done in the update-method, when the TreeView is set.

Here's the code that solved the problem:

**Constructor**
public CustomTreeCellFactory(){
    try {
        hBox = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCell.fxml"));
    } catch (IOException e) {
        System.out.println("This didn't work");
        e.printStackTrace();
    }
    try {
        hBoxLeaf = (HBox) FXMLLoader.load(getClass().getResource("/Views/TreCellLowestLevel.fxml"));
    } catch (IOException e) {
        System.out.println("This didn't work");
        e.printStackTrace();
    }

}

Update Method

@Override
public void updateItem(String item, boolean empty) {
   super.updateItem(item, empty);

    if (item != null) {
        if (getTreeView().getTreeItemLevel(getTreeItem())==1) {
            setGraphic(this.hBox);
        }else if (getTreeView().getTreeItemLevel(getTreeItem())==2){
            setGraphic(this.hBoxLeaf);
        }
    } else {
        setGraphic(null);
    }
}

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