Question

我有这个方法：

private ArrayList<Image> imageArray(File files[]) {

    ArrayList<Image> images = null;

    for(int x = 0; files.length > x; x++) {

        //I want to add each PNG-File to the Image-Array

        try {
            images.add(x, ImageIO.read(files[x])); //Demo.imageArray(Demo.java:23)
        }catch(IOException | ArrayIndexOutOfBoundsException exception) {
            exception.printStackTrace();
        }

        //Now I scale each Image, so it fits the screenSize

        int newWidth = (int) screenSize.getWidth(),
            newHeight = newWidth * images.get(x).getHeight(null) / images.get(x).getWidth(null);

        if(newHeight > screenSize.getHeight()) {

            newHeight = (int) screenSize.getHeight();
            newWidth = newHeight * images.get(x).getWidth(null) / images.get(x).getHeight(null);
        }

        images.set(x, images.get(x).getScaledInstance(newWidth, newHeight, Image.SCALE_SMOOTH));
    }

    return images;
}

导致此异常：

Exception in thread "main" java.lang.NullPointerException
    at Demo.imageArray(Demo.java:23) //I've marked the position in the code!
    at Demo.main(Demo.java:47) // Just, when I want to use the method anywhere

为什么我会收到错误，我该如何解决？当我想使用方法时，我添加了一个参数，如下所示：

imageArray(new File[] {new File("filePath to PNG-Image"),
            new File("filePath to PNG-Image")})

Answer 1

一个简单的解决方案是初始化images。

所以不要只是这样做：

ArrayList<Image> images = null;

这样做：

ArrayList<Image> images = new ArrayList<>();

如何将PNG-File-Array添加到ArrayList <img/> - Java

1 个答案: