使用 AsyncTask 显示输入流文件读取进度

Question

我想显示正在读取的文件的进度，并将其放入数组列表中。这样做时，在应用程序以列表视图向用户显示数组列表之前，我想显示通过 AsyncTask 读取了多少文件。目前短暂显示白屏。正在读取的文件由大约 20000 行组成。

AsyncTask( MyTask)在onCreate()方法中执行，如下：

 private class MyAsync extends AsyncTask<Void, Integer, ArrayList<Movie>> {

    ProgressDialog mProgressDialog;

    ArrayList<Movie> movies;

    @Override

    protected void onPreExecute() {

        super.onPreExecute();

        //Show progress to user

        mProgressDialog = new ProgressDialog(MovieRatingsActivity.this);

        mProgressDialog.setTitle("Reading file");

        mProgressDialog.setMessage("Reading file, Please Wait!");

        mProgressDialog.setIndeterminate(false);

        mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

        mProgressDialog.show();

    }

    @Override

    protected ArrayList<Movie> doInBackground(Void... voids) {

        try {

            InputStream inputStream = getResources().openRawResource(R.raw.ratings);

            int count = inputStream.available();

            // onProgressUpdate( (amount read by inputstream / size of file )* 100 );

            movies = Movie.loadFromFile(inputStream);

            return movies;

        } catch (Exception e) {

            e.printStackTrace();

        }

        return null;

    }

    @Override

    protected void onProgressUpdate(Integer... progress) {

        super.onProgressUpdate(progress);

        mProgressDialog.setProgress(progress[0]);

    }

    @Override

    protected void onPostExecute(ArrayList<Movie> movies) {

        super.onPostExecute(movies);

        mProgressDialog.dismiss();

        mInflater = (LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        setListAdapter(new RowIconAdapter(getApplicationContext(), R.layout.listrow, R.id.row_label, movies));

    }

}

Answer 1

内部doInBackground()调用publishProgress(value)，其中 value 是一个整数，表示已完成工作的百分比。这将触发onProgressUpdate()并且您获得先前传递的值progress[0]，然后您可以相应地更新进度条。编辑工作完成百分比的计算只能在while循环中进行loadFromFile()。因此，在这种情况下，更容易loadFromFile()将其所有代码删除并放入doInBackground(). 然后像这样修改循环：int counter = 0;while ((line = br.readLine()) != null) {&nbsp; &nbsp; String lRatings = line.substring(0,3).trim();&nbsp; &nbsp; String lVotes = line.substring(4,12).trim();&nbsp; &nbsp; String lName = line.substring(13).trim();&nbsp; &nbsp; movies.add(new Movie(lName, lRatings, lVotes));&nbsp; &nbsp; counter++;&nbsp; &nbsp; if ((counter % 200) == 0)&nbsp; &nbsp; &nbsp; &nbsp; publishProgress(counter / 200)}&nbsp;该值counter / 200将是已完成工作的 1%，但如果它很耗时，您可以更改它