他们为什么检查WeakReference是否为null？

Question

这是有关android开发人员的博客文章，介绍如何异步下载图像： http : //android-developers.blogspot.de/2010/07/multithreading-for-performance.html

来自的代码片段：

class BitmapDownloaderTask extends AsyncTask<String, Void, Bitmap> {
    private String url;
    private final WeakReference<ImageView> imageViewReference;

    public BitmapDownloaderTask(ImageView imageView) {
        imageViewReference = new WeakReference<ImageView>(imageView);
    }

    @Override
    // Actual download method, run in the task thread
    protected Bitmap doInBackground(String... params) {
         // params comes from the execute() call: params[0] is the url.
         return downloadBitmap(params[0]);
    }

    @Override
    // Once the image is downloaded, associates it to the imageView
    protected void onPostExecute(Bitmap bitmap) {
        if (isCancelled()) {
            bitmap = null;
        }

        if (imageViewReference != null) {
            ImageView imageView = imageViewReference.get();
            if (imageView != null) {
                imageView.setImageBitmap(bitmap);
            }
        }
    }
}

问题：为什么他们要检查imageViewReference是否为null？ 那是拼写错误吗？

Answer 1

看起来真的很陈旧。 删除此检查，不会发生任何不良情况。