JavaFX：使用 Filechooser 移动文件后，图像未显示在 ImageView 中

Question

在我的 JavaFX GUI 中，用户可以编辑他们的帖子，这涉及将现有图像更改为用户上传的图像。 这就是下面显示的 function 的用武之地。

postImage 是我从 FXML 文件中引用的 ImageView - @FXML private ImageView postImage;

private void uploadImage(ActionEvent actionEvent) {
        // Create fileChooser
        FileChooser fileChooser = new FileChooser();
        FileChooser.ExtensionFilter extFilterImages = new FileChooser.ExtensionFilter("Image files (*.jpg)", "*.JPG", "*.PNG");
        fileChooser.getExtensionFilters().addAll(extFilterImages);

        // open dialog to have user select an image from the file system
        File selectedFile = fileChooser.showOpenDialog(title.getScene().getWindow());

        if (selectedFile != null) {
            System.out.println("File selected:" + selectedFile);
            System.out.println("Selected Image: " + selectedFile.getName());

            Path source = FileSystems.getDefault().getPath(selectedFile.getPath());
            String fileExtension = selectedFile.getName().substring(selectedFile.getName().lastIndexOf("."));
            String imagePath = "newImageUploaded" + fileExtension;
            Path destination = FileSystems.getDefault().getPath("resources/images/" + imagePath);

            System.out.println("Source: " + source);
            System.out.println("Destination: " + destination);

            // moving the uploaded image to the resources folder
            try {
                Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);
            } catch (IOException ioException) {
                ioException.printStackTrace();
                System.out.println("Exception Caught");
            }

            System.out.println("Changing image: " + imagePath);

            // Set the uploaded image in the ImageView in GUI.
            postImage.setImage(new Image("/images/" + imagePath)); // error on this line: PostDetailsController.java:326

        }

    }

当这个 function 运行时，图像被成功移动并出现在我的资源文件夹中。 但是，最后一行postImage.setImage(new Image("/images/" + imagePath)); 应该更新我的图像给我以下错误：

File selected:/Users/vaishnavinaik/Downloads/shoes.jpg
Selected Image: shoes.jpg
Source: /Users/vaishnavinaik/Downloads/shoes.jpg
Destination: resources/images/newImageUploaded.jpg
Changing image: newImageUploaded.jpg
Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: Invalid URL: Invalid URL or resource not found
    at javafx.graphics/javafx.scene.image.Image.validateUrl(Image.java:1107)
    at javafx.graphics/javafx.scene.image.Image.<init>(Image.java:617)
    at controller.PostDetailsController.uploadImage(PostDetailsController.java:326)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics/javafx.scene.Node.fireEvent(Node.java:8879)
    at javafx.controls/javafx.scene.control.Button.fire(Button.java:200)
    at javafx.controls/com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:206)
    at javafx.controls/com.sun.javafx.scene.control.inputmap.InputMap.handle(InputMap.java:274)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
    at javafx.base/com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at javafx.base/com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at javafx.base/com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at javafx.base/com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
    at javafx.base/com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
    at javafx.base/javafx.event.Event.fireEvent(Event.java:198)
    at javafx.graphics/javafx.scene.Scene$MouseHandler.process(Scene.java:3851)
    at javafx.graphics/javafx.scene.Scene$MouseHandler.access$1200(Scene.java:3579)
    at javafx.graphics/javafx.scene.Scene.processMouseEvent(Scene.java:1849)
    at javafx.graphics/javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2588)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:397)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:434)
    at javafx.graphics/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:390)
    at javafx.graphics/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:433)
    at javafx.graphics/com.sun.glass.ui.View.handleMouseEvent(View.java:556)
    at javafx.graphics/com.sun.glass.ui.View.notifyMouse(View.java:942)
    at javafx.graphics/com.sun.glass.ui.mac.MacView.notifyMouse(MacView.java:127)
Caused by: java.lang.IllegalArgumentException: Invalid URL or resource not found
    at javafx.graphics/javafx.scene.image.Image.validateUrl(Image.java:1099)
    ... 46 more

有没有可能当语句postImage.setImage(new Image("/images/" + imagePath)); 已执行，移动尚未完成？ 将图像设置为 imageView 时我做错了什么吗？

Answer 1

Image构造函数期望将表示URL的String传递给它。 如文档中所述

如果传递的字符串不是有效的 URL，而是路径，则在这种情况下会在类路径中搜索图像。

因此，您在这里有效地尝试做的是在运行时修改类路径的内容； 这是不可行的（例如，如果应用程序从 jar 文件运行，这在生产中几乎肯定是正确的，您将不得不在运行时修改该 jar 文件的内容，这可能是不可能的）。

假设这里的目的是保留图像，以便在用户下次运行应用程序时可用，通常的方法是将图像复制到用户系统上的文件夹，该文件夹旨在存储应用程序的用户特定数据。 （替代方法可能是将图像数据存储在本地或远程的数据库中，具体取决于应用程序。）一种常见的方案是使用名称以. 并包含应用程序的名称，并且位于用户的主目录中：

Path applicationDataPath = Paths.get(System.getProperty("user.home"), ".my-application");
Files.createDirectories(applicationDataPath);

现在你可以做

Path destination = applicationDataPath.resolve("newImageUploaded"+fileExtension);

try {

    Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);

    System.out.println("Changing image: " + imagePath);

    // Set the uploaded image in the ImageView in GUI.
    postImage.setImage(new Image(destination.toUri().toURL().toExternalForm())); 

} catch (IOException ioException) {
    ioException.printStackTrace();
    System.out.println("Exception Caught");
}

您还可以相当轻松地，例如，在应用程序启动时检查该文件是否存在，并根据需要显示图像等。