小编zoe*_*oey的帖子

什么getActivity()意思？我在某个地方看到,他们写的MainActivity.this.startActionMode(mActionModeCallback)不是getActivity().有人可以解释这两行是什么意思吗？

  someView.setOnLongClickListener(new View.OnLongClickListener() {
        // Called when the user long-clicks on someView
        public boolean onLongClick(View view) {
            if (mActionMode != null) {
                return false;
            }

            // Start the CAB using the ActionMode.Callback defined above
            mActionMode = getActivity().startActionMode(mActionModeCallback);
            view.setSelected(true);
            return true;
        }
    });

每个函数中的"......"是什么意思？为什么在最后一个函数中,没有"......"？

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
     protected Long doInBackground(URL... urls) {
         int count = urls.length;
         long totalSize = 0;
         for (int i = 0; i < count; i++) {
             totalSize += Downloader.downloadFile(urls[i]);
             publishProgress((int) ((i / (float) count) * 100));
             // Escape early if cancel() is called
             if (isCancelled()) break;
         }
         return totalSize;
     }

     protected void onProgressUpdate(Integer... progress) {
         setProgressPercent(progress[0]);
     }

     protected void onPostExecute(Long result) {
         showDialog("Downloaded " + result + " bytes");
     }
 }

android中这两个Contacts.CONTENT_FILTER_URI和 Contacts.CONTENT_URI有什么区别？

n*log2(n) = A,具有A已知值.我如何n在Matlab中解决？注意,n不必是整数.