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从后台线程更新可观察列表的正确方法

java-threads observable javafx multithreading java

APK · 技术社区 · 7 年前

我正试图在测试项目中遵循MVC,因此我的模型应该完全独立于我的视图,但是我不确定如何更新在后台线程中更新的可观察列表(它被赋予了通过FTP上传文件的字符串),以便消息显示在ListView的UI上。

现在,以下代码实际上“按预期工作”,只是没有正确建模,我不确定如何正确建模。一些初步的研究表明,我可能需要使用Observer和observable,中间还有一个类作为我的observable列表,但我不确定该如何设置。

所以我有一个可观察的列表,它在后台线程上更新:

private ObservableList<String> transferMessages;

public FTPUtil(String host, int port, String user, String pass) {
    this.host = host;
    this.port = port;
    this.username = user;
    this.password = pass;       

    transferMessages = FXCollections.observableArrayList();

    connect();
}

public void upload(File src) {
    System.out.println("Uploading: " + src.getName());
    try {
        if (src.isDirectory()) {            
            ftpClient.makeDirectory(src.getName());
            ftpClient.changeWorkingDirectory(src.getName());
            for (File file : src.listFiles()) {
                upload(file);
            }
            ftpClient.changeToParentDirectory();
        } else {
            InputStream srcStream = null;
            try {
                addMessage("Uploading: " + src.getName());
                srcStream = src.toURI().toURL().openStream();
                ftpClient.storeFile(src.getName(), srcStream);
                addMessage("Uploaded: " + src.getName() + " - Successfully.");

            } catch (Exception ex) {
                System.out.println(ex);
                addMessage("Error Uploading: " + src.getName() + " - Speak to Administrator.");
            }
        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}

private void addMessage(String message){

    Platform.runLater(() -> transferMessages.add(0, message));

}

FTPUtil类是我的模型。

我还有一个模型管理器类,它控制这个FTPUtil类:

public class ModelManager {

private ObservableList<String> fileAndFolderLocations;


private FTPUtil ftpUtil;

public ModelManager(String host, int port, String user, String pass) {

    ftpUtil = new FTPUtil(host, port, user, pass);
    fileAndFolderLocations = FXCollections.observableArrayList();

}

public boolean startBackup() {

    Task task = new Task() {
        @Override
        protected Object call() throws Exception {

            System.out.println("I started");
            ftpUtil.clearMessages();

            for(String location : fileAndFolderLocations){
                File localDirPath = new File(location);         
                ftpUtil.upload(localDirPath);
            }               
            return null;
        }           
    };      
    new Thread(task).start();

    return true;
}

public void addFileOrFolder(String fileOrFolder){
    if(!fileAndFolderLocations.contains(fileOrFolder)){
        fileAndFolderLocations.add(fileOrFolder);
    }       
}

public boolean removeFileOrFolder(String fileOrFolder){
    return fileAndFolderLocations.remove(fileOrFolder);
}

public ObservableList<String> getFilesAndFoldersList() {
    return fileAndFolderLocations;
}

public ObservableList<String> getMessages() {
    return ftpUtil.getMessages();
}

}

最后是我的GUI:

public class BackupController {

private Main main;
private ModelManager mm;

@FXML
private ListView<String> messagesList;

@FXML
void forceBackup(ActionEvent event) {
    mm.startBackup();           

}

public void initController(Main main, ModelManager mm) {
    this.main = main;
    this.mm = mm;

    messagesList.setItems(mm.getMessages());
}


}

2 回复 | 直到 7 年前

kleopatra Aji kattacherry 7 年前

基本设置:

不要使用平台。在模型中稍后运行
不要将模型/经理的消息列表直接设置为列表视图中的项目
一定要保留一个单独的项目观察列表,并将其设置为列表

一个非常原始的片段来说明设置:

private Parent getContent() {
    ModelManager manager = new ModelManager();
    ObservableList<String> uploading = FXCollections.observableArrayList("one", "two", "three");

    ObservableList<String> items = FXCollections.observableArrayList();
    manager.getMessages().addListener((ListChangeListener) c -> {

        while (c.next()) {
            if (c.wasAdded()) {
                Platform.runLater(() ->  
                    items.addAll(c.getFrom(), c.getAddedSubList()));
            } 
            if (c.wasRemoved()) {
                Platform.runLater(() ->
                     items.removeAll(c.getRemoved()));
            }
        }
    });


    ListView<String> list = new ListView<>(items);
    Button button = new Button("start");
    button.setOnAction(ev -> {
        uploading.stream().forEach(e -> manager.addFile(e));
        manager.startBackup();
    });
    BorderPane pane = new BorderPane(list);
    pane.setBottom(button);
    return pane;
}

@Override
public void start(Stage stage) throws Exception {
    Scene scene = new Scene(getContent());
    stage.setScene(scene);
    stage.show();
}

Tobias Diez 5 年前

您需要一个围绕列表的包装器,将更改发布到正确的线程上。

ObservableList<String> source = FXCollections.observableArrayList();
ObservableList<String> items = new UiThreadList(source);
ListView<String> list = new ListView<>(items);

具有

import javafx.application.Platform;
import javafx.collections.ListChangeListener;
import javafx.collections.ObservableList;
import javafx.collections.transformation.TransformationList;

class UiThreadList<T> extends TransformationList<T, T> {
    public UiThreadList(ObservableList<? extends T> source) {
        super(source);
    }

    @Override
    protected void sourceChanged(ListChangeListener.Change<? extends T> change) {
        Platform.runLater(() -> fireChange(change));
    }

    @Override
    public int getSourceIndex(int index) {
        return index;
    }

    @Override
    public T get(int index) {
        return getSource().get(index);
    }

    @Override
    public int size() {
        return getSource().size();
    }
}

这个解决方案的思想类似于上面的@kleopatra。