使用 AsyncTask 显示输入流文件读取进度

Question

我想显示正在读取文件并将其放入数组列表的进度。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。当前短暂显示白屏。正在读取的文件包含大约 20000 行。

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));
    }
}

函数Movie.loadFromFile(inputStream) - 这是将数据放入数组列表的地方

    /** Loads movie information from a raw resource file */
public static ArrayList<Movie> loadFromFile(InputStream inputStream) {
    ArrayList<Movie> movies = new ArrayList<Movie>(20000);
    BufferedReader br = new BufferedReader(new InputStreamReader(inputStream));
    String line;
    try {
        while ((line = br.readLine()) != null) {
            String lRatings = line.substring(0,3).trim();
            String lVotes = line.substring(4,12).trim();
            String lName = line.substring(13).trim();
            movies.add(new Movie(lName, lRatings, lVotes));
        }
    } catch (IOException iox) { } // pure evil at work
    return movies;
}

Answer 1

在 doInBackground() 中调用 publishProgress(value)，其中值是一个整数，表示已完成工作的百分比。
这将触发 onProgressUpdate() 并且您在 progress[0] 中获得先前传递的值，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loadFromFile()的while循环中进行。所以在这种情况下，删除 loadFromFile() 并将其所有代码放在 doInBackground() 中会更容易。然后像这样修改循环：

int counter = 0;
while ((line = br.readLine()) != null) {
    String lRatings = line.substring(0,3).trim();
    String lVotes = line.substring(4,12).trim();
    String lName = line.substring(13).trim();
    movies.add(new Movie(lName, lRatings, lVotes));
    counter++;
    if ((counter % 200) == 0)
        publishProgress(counter / 200)
}

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

使用 AsyncTask 显示输入流文件读取进度

Showing inputstream file read progress with AsyncTask

java

android

inputstream

android-asynctask

progress-bar