如何动态更改ImageView？

Question

Langauge

Java

Application:

I'm trying to create a basic image searcher where I enter a UPC and show a product image on the ImageView.

Question

How can dynamically update the ImageView with a new image without creating new instances as I'm doing in my current implementation below .

Current Implementation:

In my current implementation I have the event handler create a new image and have it set into the ImageView.

        searchButton.setOnAction(new EventHandler<ActionEvent>() {
        public void handle(ActionEvent e)
        {
            input = searchBar.getText();
            image = new Image("url link" + input);
            imageView.setImage(image);
            searchBar.clear();
        }
    });

Answer 1

The short answer is, it is unavoidable. This implementation is perfectly normal. When you create a new Image , and set it to the ImageView , the old Image loses the reference and is eligible for garbage collection.

The long answer is, you can control this behavior to certain extent. You can keep a cache of these images with the help of SoftReference .

Map<String, SoftReference<Image>> imageCache = new HashMap<>();

.....

searchButton.setOnAction(new EventHandler<ActionEvent>() {
    public void handle(ActionEvent e)
    {
        input = searchBar.getText();
        final String urlString = "url link" + input; // Or whatever the URL

        final SoftReference<Image> softRef = imageCache.get(urlString);
        Image image = null;

        if (softRef == null || softRef.get() == null) {
            image = new Image(urlString);
            imageCache.put(urlString, new SoftReference<>(image));
        }
        else
            image = softRef.get();

        imageView.setImage(image);
        searchBar.clear();
    }
});

This will allows your controller to store a cache of images until the Java Heap runs out of space.