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[英]How do I make a mouse click event be acknowledged by a TreeItem in a TreeView?
[英]How do I make JavaFX TreeView and TreeItem serializable?
嘗試使用 ObjectOutputStream.保存我的 TreeView 時出現此錯誤
我有 2 個實現 Serializable 的類和 1 個不實現 Serializable 的主要 class。
2類是供應商和地址。 供應商 class 包含 4 個變量(姓名、年齡、性別、地址 class 類型的地址),使用 set 方法設置所有變量的構造函數,使用 set 方法僅設置名稱變量的構造函數,以及 get/set 方法變量。
地址 class 包含 2 個變量(街道名稱和郵政編碼),使用 set 方法設置變量的默認構造函數,以及變量的 get/set 方法。
這是我的主要 class
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.layout.VBox;
import javafx.stage.FileChooser;
import javafx.stage.Stage;
import java.io.File;
import java.io.FileOutputStream;
import java.io.ObjectOutputStream;
public class SimpleTreeView extends Application {
private TreeView<Vendor> treeView;
public void start(Stage stage) {
stage.setTitle("Simple TreeView");
treeView = new TreeView<>();
TreeItem<Vendor> root = new TreeItem<>(new Vendor("Root"));
root.setExpanded(true);
treeView.setRoot(root);
treeView.setShowRoot(false);
TreeItem<Vendor> start = new TreeItem<>(new Vendor("Start"));
root.getChildren().add(start);
Button saveButton = new Button("Save");
saveButton.setOnMouseClicked(event -> saveTreeView(stage));
VBox vBox = new VBox(20);
vBox.getChildren().addAll(treeView, saveButton);
stage.setScene(new Scene(vBox));
stage.show();
}
private void saveTreeView(Stage stage) {
FileChooser fileChooser = new FileChooser();
fileChooser.setTitle("Save");
File file = fileChooser.showSaveDialog(stage);
if (file != null) {
try {
ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(file));
os.writeObject(treeView);
os.close();
}
catch (Exception e) {
System.out.println(e);
}
}
}
public static void main(String[] args) {
launch(args);
}
}
節點無法序列化(可能除了您自己實現的自定義節點)有太多內部狀態太復雜而無法恢復。 由於無法向節點添加方法/接口(不擴展它們),因此無法添加Serializable
接口並添加方法來保存恢復 state 和正確讀取此數據所需的數據部分。
您最好創建一個可序列化的包裝器 class ,它允許您恢復您真正感興趣的屬性。恕我直言,最好不要嘗試序列化節點; 加載數據時創建一個新節點,並用加載的數據填充它。
以下示例顯示了如何使用TreeItem<? extends Serializable>
TreeItem<? extends Serializable>
; 缺少諸如擴展屬性之類的數據,但是您應該能夠恢復value
屬性和子項。 (實現比深度較小的TreeItem
結構所需的復雜一些,但您需要注意某些深度,更簡單的遞歸方法可能會導致StackOverflowError
s。)
在這種情況下,通過寫入子項的數量、它自己的 value 屬性對每個項進行序列化,然后對每個子項執行相同的操作。 這會產生一系列可用於恢復數據的 int 和 value 對:
public class TreeItemSerialisation {
public static void main(String[] args) throws IOException, ClassNotFoundException {
TreeItem<String> root = new TreeItem<>("root");
TreeItem<String> c1 = new TreeItem<>("root.1");
TreeItem<String> c3 = new TreeItem<>("root.3");
root.getChildren().addAll(c1, new TreeItem<>("root.2"), c3);
TreeItem<String> c3_1 = new TreeItem<>("root.3.1");
c3_1.getChildren().add(new TreeItem<>("root.3.1.1"));
c3.getChildren().add(c3_1);
c1.getChildren().addAll(new TreeItem<>("root.1.1"), new TreeItem<>("root.1.2"));
// serialize
ByteArrayOutputStream bos = new ByteArrayOutputStream();
try (ObjectOutputStream oos = new ObjectOutputStream(bos)) {
oos.writeObject(new TreeItemSerialisationWrapper(root));
}
// unserialize
TreeItem<String> root2;
try (ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(bos.toByteArray()))) {
root2 = (TreeItem<String>) ois.readObject();
}
// TODO do something with root2
}
}
public class TreeItemSerialisationWrapper<T extends Serializable> implements Serializable {
private static final long serialVersionUID = 1L;
private transient TreeItem<T> item;
public TreeItemSerialisationWrapper(TreeItem<T> item) {
if (item == null) {
throw new IllegalArgumentException();
}
this.item = item;
}
/**
* Custom way of writing the TreeItem structure
*/
private void writeObject(ObjectOutputStream out)
throws IOException {
Stack<TreeItem<T>> stack = new Stack<>();
stack.push(item);
out.defaultWriteObject();
do {
TreeItem<T> current = stack.pop();
int size = current.getChildren().size();
out.writeInt(size);
// write all the data that needs to be restored here
out.writeObject(current.getValue());
// "schedule" serialisation of children.
// the first one is inserted last, since the top one from the stack is
// retrieved first
for (int i = size - 1; i >= 0; --i) {
stack.push(current.getChildren().get(i));
}
} while (!stack.isEmpty());
}
/**
* happens before readResolve; recreates the TreeItem structure
*/
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException {
class Container {
int count;
final TreeItem<T> item;
Container(ObjectInputStream in) throws ClassNotFoundException, IOException {
// read the data for a single TreeItem here
this.count = in.readInt();
this.item = new TreeItem<>((T) in.readObject());
}
}
in.defaultReadObject();
Container root = new Container(in);
this.item = root.item;
if (root.count > 0) {
Stack<Container> stack = new Stack<>();
stack.push(root);
do {
Container current = stack.peek();
--current.count;
if (current.count <= 0) {
// we're done with this item
stack.pop();
}
Container newContainer = new Container(in);
current.item.getChildren().add(newContainer.item);
if (newContainer.count > 0) {
//schedule reading children of non-leaf
stack.push(newContainer);
}
} while(!stack.isEmpty());
}
}
/**
* We're not actually interested in this object but the treeitem
* @return the treeitem
* @throws ObjectStreamException
*/
private Object readResolve() throws ObjectStreamException {
return item;
}
}
有關readObject
、 readResolve
和writeObject
如何工作的描述,請參閱Serializable
的 javadoc
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