How do I make the “current directory” of the dialogs persist across
different invocations?

您可以为此修改Singleton Pattern方法

因此,您只能使用一个FileChooser并监视/控制那里的初始目录,但不会直接将该实例暴露给类外的修改

例如：

public class RetentionFileChooser {
    private static FileChooser instance = null;
    private static SimpleObjectProperty<File> lastKnownDirectoryProperty = new SimpleObjectProperty<>();

    private RetentionFileChooser(){ }

    private static FileChooser getInstance(){
        if(instance == null) {
            instance = new FileChooser();
            instance.initialDirectoryProperty().bindBidirectional(lastKnownDirectoryProperty);
            //Set the FileExtensions you want to allow
            instance.getExtensionFilters().setAll(new ExtensionFilter("png files (*.png)","*.png"));
        }
        return instance;
    }

    public static File showOpenDialog(){
        return showOpenDialog(null);
    }

    public static File showOpenDialog(Window ownerWindow){
        File chosenFile = getInstance().showOpenDialog(ownerWindow);
        if(chosenFile != null){
            //Set the property to the directory of the chosenFile so the fileChooser will open here next
            lastKnownDirectoryProperty.setValue(chosenFile.getParentFile());
        }
        return chosenFile;
    }

    public static File showSaveDialog(){
        return showSaveDialog(null);
    }

    public static File showSaveDialog(Window ownerWindow){
        File chosenFile = getInstance().showSaveDialog(ownerWindow);
        if(chosenFile != null){
            //Set the property to the directory of the chosenFile so the fileChooser will open here next
            lastKnownDirectoryProperty.setValue(chosenFile.getParentFile());
        }
        return chosenFile;
    }
}

这将把FileChooser的初始目录设置为用户上次重新打开/保存的文件的目录

用法示例：

File chosenFile = RetentionFileChooser.showOpenDialog();

但是这里有一个限制：

//Set the FileExtensions you want to allow 
instance.getExtensionFilters().setAll(new ExtensionFilter("png files (*.png)","*.png"));

由于没有提供任何ExtensionFilter,FileChooser变得不那么用户友好,要求用户手动附加文件类型,但在创建实例时提供过滤器而无法更新它们将其限制为相同的过滤器

改进这一点的一种方法是在RetentionFileChooser中公开可以使用varargs提供的可选过滤器,从而可以在显示对话框时选择修改过滤器的时间

例如,建立在前一个：

public class RetentionFileChooser {
    public enum FilterMode {
        //Setup supported filters
        PNG_FILES("png files (*.png)","*.png"),TXT_FILES("txt files (*.txt)","*.txt");

        private ExtensionFilter extensionFilter;

        FilterMode(String extensionDisplayName,String... extensions){
            extensionFilter = new ExtensionFilter(extensionDisplayName,extensions);
        }

        public ExtensionFilter getExtensionFilter(){
            return extensionFilter;
        }
    }

    private static FileChooser instance = null;
    private static SimpleObjectProperty<File> lastKnownDirectoryProperty = new SimpleObjectProperty<>();

    private RetentionFileChooser(){ }

    private static FileChooser getInstance(FilterMode... filterModes){
        if(instance == null) {
            instance = new FileChooser();
            instance.initialDirectoryProperty().bindBidirectional(lastKnownDirectoryProperty);
        }
        //Set the filters to those provided
        //You could add check's to ensure that a default filter is included,adding it if need be
        instance.getExtensionFilters().setAll(
                Arrays.stream(filterModes)
                        .map(FilterMode::getExtensionFilter)
                        .collect(Collectors.toList()));
        return instance;
    }

    public static File showOpenDialog(FilterMode... filterModes){
        return showOpenDialog(null,filterModes);
    }

    public static File showOpenDialog(Window ownerWindow,FilterMode...filterModes){
        File chosenFile = getInstance(filterModes).showOpenDialog(ownerWindow);
        if(chosenFile != null){
            lastKnownDirectoryProperty.setValue(chosenFile.getParentFile());
        }
        return chosenFile;
    }

    public static File showSaveDialog(FilterMode... filterModes){
        return showSaveDialog(null,filterModes);
    }

    public static File showSaveDialog(Window ownerWindow,FilterMode... filterModes){
        File chosenFile = getInstance(filterModes).showSaveDialog(ownerWindow);
        if(chosenFile != null){
            lastKnownDirectoryProperty.setValue(chosenFile.getParentFile());
        }
        return chosenFile;
    }
}

用法示例：

//Note the prevIoUs example still holds
File chosenFile = RetentionFileChooser.showOpenDialog();
File file = RetentionFileChooser.showSaveDialog(FilterMode.PNG_FILES);

but this does not work if the dialog is closed or canceled.

遗憾的是,FileChooser在关闭/终止之前不会公开有关正在检查的目录的信息.如果您对类进​​行反编译并进行跟踪,则最终会触发本机调用.因此即使FileChooser不是最终允许它被子类化,它也不太可能获得这些信息

上述方法提供的唯一好处是,如果遇到此情况,它不会更改初始目录

如果你有兴趣,这个问题中的本地关键词有一些非常好的答案和链接：

> What is the native keyword in Java for?