Question

我正在尝试在后台下载一些文件，因为我使用了下载管理器，并采用了以下方法：

/*** media download ***/
    public long mediaDownload(ArrayList<DownloadedFile> arrayList, String foldPathName) {
        long downloadReference = 0;

        // Create request for android download manager
        downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);

        for (int i = 0; i < arrayList.size();i++){

            DownloadManager.Request request = new DownloadManager.Request(arrayList.get(i).getUri());
            request.setTitle("Data Download");
            request.setDescription("New media");

            //Set the local destination for the downloaded file to a path
            //within the application's external files directory
            request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS + "/" + folder_main + "/" + foldPathName, arrayList.get(i).getName());
            File f = new File(Environment.DIRECTORY_DOWNLOADS + "/" + folder_main + "/" + foldPathName + "/" + arrayList.get(i).getName());
            Log.e("File:",f.toString());

            //Enqueue download and save into referenceId
            downloadReference = downloadManager.enqueue(request);

        }
        return downloadReference;
    }

我有一张图片和一个视频要下载以进行测试，当在资源管理器中检查下载的文件时，我发现有2个视频和2张图片，调试发现我发现onPostExecute方法被调用了两次，我不知道为什么。这是我的onPostExecute方法：

 protected void onPostExecute(String s) {
                try {
                    JSONObject jsonObject = new JSONObject(s);
                    JSONArray region = null;
                    region = jsonObject.getJSONArray("regions");
                    Log.e("Regions:", String.valueOf(region.length()));
                    for (int i = 0; i < region.length(); i++) {
                        try {
                            JSONObject json_data = region.getJSONObject(i);
                            int height_view = Integer.parseInt(json_data.getString("height"));
                            int width_view = Integer.parseInt(json_data.getString("width"));

                            int left_view = Integer.parseInt(json_data.getString("left"));
                            int top_view = Integer.parseInt(json_data.getString("top"));
                            int right_view = Integer.parseInt(json_data.getString("right"));
                            int bottom_view = Integer.parseInt(json_data.getString("bottom"));

                            /**** Media in region ***/
                            JSONObject media = json_data.getJSONObject("media");
                            String type_media = media.getString("type");

                            url = media.getString("url");
                            name = media.getString("name");
                            uri = Uri.parse(url);
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                        downloadedFiles.add(new DownloadedFile(name, uri));
                    }
                    Toast.makeText(MainActivity.this, "Layout Created with" + height + "x" + width, Toast.LENGTH_SHORT).show();
                } catch (Exception e) {
                    e.printStackTrace();
                }
                Log.e("Downloaded Files:",downloadedFiles.toString());
                mediaDownload(downloadedFiles, folderName); // region media's download
            }

在我的logcat上，我看到我的arrayList有2个元素，但是显示了两次，这意味着文件被下移了两次，因此onPostExecute方法被调用了两次，谢谢帮助。

Answer 1

我花了很多时间调试所有代码后才发现，创建活动时它改变了屏幕方向，因此它创建了第二个实例，所以我的AsyncTask被调用了两次，这就是为什么我以为onPosteExecute被调用了两次，谢谢给所有想帮助的人。

onPostExecute被调用两次并显示双重结果

1 个答案: