[英]Why do they check WeakReference for null?
這是有關android開發人員的博客文章,介紹如何異步下載圖像: http : //android-developers.blogspot.de/2010/07/multithreading-for-performance.html
來自的代碼片段:
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);
}
}
}
}
問題:為什么他們要檢查imageViewReference是否為null? 那是拼寫錯誤嗎?
看起來真的很陳舊。 刪除此檢查,不會發生任何不良情況。
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