android - 如何在android中的for循环中为String列表调用Async Task

Question

ArrayList<String> list1 = splitFileList;

                for (int i = 0; i < list1.size(); i++) {

                    tempFileName = splitFileList.get(i);
                    String splitFileCheckinDirectory = splitVideofilepath + Constant.SPLIT_VIDEO + "/" + list1.get(i) + Constant.FILE_EXTENSION;

                    File myfile = new File(splitFileCheckinDirectory);
                    if (!myfile.exists()) {
                        new TrimmVideo(getExternalFilesDir(null) + "/" + getFileNameFromFilePath(mFilePath), mStartTImelist.get(i), mEndTimelist.get(i) - mStartTImelist.get(i)).execute();

                    }
                   }

下面是我尝试在 for 循环中执行的 Asynktask

private class TrimmVideo extends AsyncTask<Void, Void, Void> {
        private final String mediaPath;
        private final double endTime;
        private final int length;
        private double startTime;
        private ProgressDialog progressDialog;

        private TrimmVideo(String mediaPath, int startTime, int length) {
            this.mediaPath = mediaPath;
            this.startTime = startTime;
            this.length = length;
            this.endTime = this.startTime + this.length;
        }

        @Override
        protected void onPreExecute() {
            progressDialog = ProgressDialog.show(VideoPlayActvity.this,
                    "Trimming videos", "Please wait...", true);
            super.onPreExecute();
        }

        @Override
        protected Void doInBackground(Void... params) {
            trimVideo();
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            progressDialog.dismiss();
            dbHandler.updateFlag(fileModel == null ? tempFileName : fileModel.getfilename());
            btn_save_video.setVisibility(View.INVISIBLE);
            super.onPostExecute(result);
        }

        private void trimVideo() {
            try {
                File file = new File(mediaPath);
                FileInputStream fis = new FileInputStream(file);
                FileChannel in = fis.getChannel();
                Movie movie = MovieCreator.build(in);

                List<Track> tracks = movie.getTracks();
                movie.setTracks(new LinkedList<Track>());

                boolean timeCorrected = false;

                // Here we try to find a track that has sync samples. Since we can only start decoding
                // at such a sample we SHOULD make sure that the start of the new fragment is exactly
                // such a frame
                for (Track track : tracks) {
                    if (track.getSyncSamples() != null && track.getSyncSamples().length > 0) {
                        if (timeCorrected) {
                            // This exception here could be a false positive in case we have multiple tracks
                            // with sync samples at exactly the same positions. E.g. a single movie containing
                            // multiple qualities of the same video (Microsoft Smooth Streaming file)

                            //throw new RuntimeException("The startTime has already been corrected by another track with SyncSample. Not Supported.");
                        } else {
                            startTime = correctTimeToNextSyncSample(track, startTime);
                            timeCorrected = true;
                        }
                    }
                }

                for (Track track : tracks) {
                    long currentSample = 0;
                    double currentTime = 0;
                    long startSample = -1;
                    long endSample = -1;

                    for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
                        TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
                        for (int j = 0; j < entry.getCount(); j++) {
                            // entry.getDelta() is the amount of time the current sample covers.

                            if (currentTime <= startTime) {
                                // current sample is still before the new starttime
                                startSample = currentSample;
                            } else if (currentTime <= endTime) {
                                // current sample is after the new start time and still before the new endtime
                                endSample = currentSample;
                            } else {
                                // current sample is after the end of the cropped video
                                break;
                            }
                            currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
                            currentSample++;
                        }
                    }
                    movie.addTrack(new CroppedTrack(track, startSample, endSample));
                }

                IsoFile out = new DefaultMp4Builder().build(movie);
                File storagePath = new File(getExternalFilesDir(null) + "/" + Constant.SPLIT_VIDEO + "/");
                storagePath.mkdirs();
                File myMovie = new File(storagePath, fileModel == null ? "/" + tempFileName + Constant.FILE_EXTENSION : fileModel.getfilename() + Constant.FILE_EXTENSION);
                FileOutputStream fos = new FileOutputStream(myMovie);
                FileChannel fc = fos.getChannel();
                out.getBox(fc);
                dbHandler.updateFlag(fileModel == null ? tempFileName : fileModel.getfilename());
                fc.close();
                fos.close();
                fis.close();
                in.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        private double correctTimeToNextSyncSample(Track track, double cutHere) {
            double[] timeOfSyncSamples = new double[track.getSyncSamples().length];
            long currentSample = 0;
            double currentTime = 0;
            for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
                TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
                for (int j = 0; j < entry.getCount(); j++) {
                    if (Arrays.binarySearch(track.getSyncSamples(), currentSample + 1) >= 0) {
                        // samples always start with 1 but we start with zero therefore +1
                        timeOfSyncSamples[Arrays.binarySearch(track.getSyncSamples(), currentSample + 1)] = currentTime;
                    }
                    currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
                    currentSample++;
                }
            }
            for (double timeOfSyncSample : timeOfSyncSamples) {
                if (timeOfSyncSample > cutHere) {
                    return timeOfSyncSample;
                }
            }
            return timeOfSyncSamples[timeOfSyncSamples.length - 1];
        }
    }

splitFileList 列表包含 2 个大小的数据 a,b 我想一个一个同步执行，即循环从 0 开始然后它应该完成 0 的异步任务然后如果循环将进入一个那么它应该完成请建议我如何执行异步任务在 for 循环中一个一个。

Answer 1

你不能通过 AsyncTask 同步运行你必须像这样使用线程:

Thread t = new Thread(
        new Runnable() {
            public void run() {
                try {
ArrayList<String> list1 = splitFileList;

            for (int i = 0; i < list1.size(); i++) {

                tempFileName = splitFileList.get(i);
                String splitFileCheckinDirectory = splitVideofilepath + Constant.SPLIT_VIDEO + "/" + list1.get(i) + Constant.FILE_EXTENSION;

                File myfile = new File(splitFileCheckinDirectory);
                if (!myfile.exists()) {
                    trimVideo(getExternalFilesDir(null) + "/" + getFileNameFromFilePath(mFilePath), mStartTImelist.get(i), mEndTimelist.get(i) - mStartTImelist.get(i)); //here you can run synchronously work
                    }
                 }
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
t.start();
try {
    t.join();
.....
} catch (Exception e) {
    e.printStackTrace();
}




 private void trimVideo(String mediaPath, int startTime, int length) {
        try {
            File file = new File(mediaPath);
            FileInputStream fis = new FileInputStream(file);
            FileChannel in = fis.getChannel();
            Movie movie = MovieCreator.build(in);

            List<Track> tracks = movie.getTracks();
            movie.setTracks(new LinkedList<Track>());

            boolean timeCorrected = false;

            // Here we try to find a track that has sync samples. Since we can only start decoding
            // at such a sample we SHOULD make sure that the start of the new fragment is exactly
            // such a frame
            for (Track track : tracks) {
                if (track.getSyncSamples() != null && track.getSyncSamples().length > 0) {
                    if (timeCorrected) {
                        // This exception here could be a false positive in case we have multiple tracks
                        // with sync samples at exactly the same positions. E.g. a single movie containing
                        // multiple qualities of the same video (Microsoft Smooth Streaming file)

                        //throw new RuntimeException("The startTime has already been corrected by another track with SyncSample. Not Supported.");
                    } else {
                        startTime = correctTimeToNextSyncSample(track, startTime);
                        timeCorrected = true;
                    }
                }
            }

            for (Track track : tracks) {
                long currentSample = 0;
                double currentTime = 0;
                long startSample = -1;
                long endSample = -1;

                for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
                    TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
                    for (int j = 0; j < entry.getCount(); j++) {
                        // entry.getDelta() is the amount of time the current sample covers.

                        if (currentTime <= startTime) {
                            // current sample is still before the new starttime
                            startSample = currentSample;
                        } else if (currentTime <= endTime) {
                            // current sample is after the new start time and still before the new endtime
                            endSample = currentSample;
                        } else {
                            // current sample is after the end of the cropped video
                            break;
                        }
                        currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
                        currentSample++;
                    }
                }
                movie.addTrack(new CroppedTrack(track, startSample, endSample));
            }

            IsoFile out = new DefaultMp4Builder().build(movie);
            File storagePath = new File(getExternalFilesDir(null) + "/" + Constant.SPLIT_VIDEO + "/");
            storagePath.mkdirs();
            File myMovie = new File(storagePath, fileModel == null ? "/" + tempFileName + Constant.FILE_EXTENSION : fileModel.getfilename() + Constant.FILE_EXTENSION);
            FileOutputStream fos = new FileOutputStream(myMovie);
            FileChannel fc = fos.getChannel();
            out.getBox(fc);
            dbHandler.updateFlag(fileModel == null ? tempFileName : fileModel.getfilename());
            fc.close();
            fos.close();
            fis.close();
            in.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private double correctTimeToNextSyncSample(Track track, double cutHere) {
        double[] timeOfSyncSamples = new double[track.getSyncSamples().length];
        long currentSample = 0;
        double currentTime = 0;
        for (int i = 0; i < track.getDecodingTimeEntries().size(); i++) {
            TimeToSampleBox.Entry entry = track.getDecodingTimeEntries().get(i);
            for (int j = 0; j < entry.getCount(); j++) {
                if (Arrays.binarySearch(track.getSyncSamples(), currentSample + 1) >= 0) {
                    // samples always start with 1 but we start with zero therefore +1
                    timeOfSyncSamples[Arrays.binarySearch(track.getSyncSamples(), currentSample + 1)] = currentTime;
                }
                currentTime += (double) entry.getDelta() / (double) track.getTrackMetaData().getTimescale();
                currentSample++;
            }
        }
        for (double timeOfSyncSample : timeOfSyncSamples) {
            if (timeOfSyncSample > cutHere) {
                return timeOfSyncSample;
            }
        }
        return timeOfSyncSamples[timeOfSyncSamples.length - 1];
    }