android - FileDownloader：监听器的任务无法启动

Question

我使用this library，但是当我在我的应用中按“刷新”按钮时，此库会显示错误：

public void refreshList() {
    if (isOnline()) {
        FileDownloader.getImpl().pauseAll();
        final RestServiceApi apiService = ServiceGenerator.createService(RestServiceApi.class, getString(R.string.base_url), remindToken());
        getContent(apiService);
    } else {
        Toast.makeText(MainActivity.this, getString(R.string.no_internet_connection), Toast.LENGTH_SHORT).show();
    }
}

onClick按钮“刷新”：

public void saveFilesOnDisk(final List<Folder> folders, final int index) {


        final List<File> files = folders.get(index).getFiles();
        progressBar.setProgress(0);
        progressBar.setMax(files.size());

        String downloaderFile = "";

        final FileDownloadListener queueTarget = new FileDownloadSampleListener() {

            @Override
            protected void pending(BaseDownloadTask task, int soFarBytes, int totalBytes) {
                Log.i("status: ", "pending");
                super.pending(task, soFarBytes, totalBytes);

            }

            @Override
            protected void progress(BaseDownloadTask task, int soFarBytes, int totalBytes) {
                Log.i("status: ", "progress");
                super.progress(task, soFarBytes, totalBytes);
            }

            @Override
            protected void error(BaseDownloadTask task, Throwable e) {
                Log.i("status: ", "error");
                super.error(task, e);
                //task.reuse();
                //saveFilesOnDisk(folders, 0);
            }

            @Override
            protected void connected(BaseDownloadTask task, String etag, boolean isContinue, int soFarBytes, int totalBytes) {
                super.connected(task, etag, isContinue, soFarBytes, totalBytes);
                Log.i("connected file: ", task.getPath());
            }

            @Override
            protected void paused(BaseDownloadTask task, int soFarBytes, int totalBytes) {
                Log.i("status: ", "pause");
                super.paused(task, soFarBytes, totalBytes);
            }

            @Override
            protected void completed(BaseDownloadTask task) {
                super.completed(task);
                Log.i("download: ", "completed; " + homeFolder + java.io.File.separator + task.getPath());

                progressBar.setProgress(progressBar.getProgress() + 1);

                        for (int i = 0; i < files.size(); i++) {
                            String filePath = homeFolder + java.io.File.separator + files.get(i).getPath().substring(2);
                            if (filePath.equals(task.getPath())) {
                                adapter.notifyItemChanged(i);
                            }
                        }
                if (progressBar.getProgress() == files.size() - 1) {
                    if (index < folders.size() - 1) {
                        saveFilesOnDisk(folders, index + 1);
                    }
                }
            }

            @Override
            protected void warn(BaseDownloadTask task) {
                Log.i("status: ", "warn");
                super.warn(task);
            }
        };

        for (int i = 0; i < files.size(); i++) {
            downloaderFile = files.get(i).getPath();
            String fullPath = homeFolder + java.io.File.separator + downloaderFile.substring(2);
            if (!(new java.io.File(fullPath).exists())) {

                final String url;
                boolean isDir = false;
                url = "http://..." + downloaderFile;

                FileDownloader.getImpl().create(url)
                        .setPath(fullPath, isDir)
                        .setCallbackProgressTimes(300)
                        .setMinIntervalUpdateSpeed(400)
                        .setListener(queueTarget)
                        .asInQueueTask()
                        .enqueue();

            } else {
                progressBar.setProgress(progressBar.getProgress() + 1);
                if (index == files.size() - 1) {
                    saveFilesOnDisk(folders, index + 1);
                }
            }
        }
        FileDownloader.getImpl().start(queueTarget, true);
}

getContent（apiService）获取文件列表并调用此方法：

var express = require('express');
var logger = require('morgan');
var bodyParser = require('body-parser');

var api = require('./api/index');

var app = express();


///////////////////////
// Server Middleware
///////////////////////

app.use(logger(app.get("env") === "production" ? "combined" : "dev"));

// parse application/json
app.use(bodyParser.json());

// parse application/x-www-form-urlencoded
app.use(bodyParser.urlencoded({ extended: false }));

// CORS
// This allows client applications from other domains use the API Server
app.use(function(req, res, next) {
    res.header("Access-Control-Allow-Origin", "*");
    res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
    next();
});


//////////////////
// API Queries
//////////////////

app.use('/', api);


//////////////////
// Server Setup
//////////////////

app.set("env", process.env.NODE_ENV || "development");
app.set("host", process.env.HOST || "0.0.0.0");
app.set("port", process.env.PORT || 8080);

app.listen(app.get("port"), function () {
    console.log('\n' + '**********************************');
    console.log('REST API listening on port ' + app.get("port"));
    console.log('**********************************' + '\n');
});


////////////////////
// Error Handlers
////////////////////

// catch 404 and forward to error handler
app.use(function(req, res, next) {
    var err = new Error('Not Found');
    err.status = 404;
    next(err);
});

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
    app.use(function(err, req, res, next) {
        res.status( err.code || 500 )
        .json({
            status: 'error',
            message: err
        });
    });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
    res.status(err.status || 500)
    .json({
        status: 'error',
        message: err.message
    });
});


module.exports = app;

如何处理此错误？我想获取所有文件