Android-如何从网络服务器下载文件-Android-howtodownloadfilefromwebserver

60  

Using Async task. (if not work in 4.0 then add

使用异步任务。 （如果不在4.0中工作则添加

StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy); 

)

）

call when you want to download file : new DownloadFileFromURL().execute(file_url);

当你想下载文件时调用：new DownloadFileFromURL（）。execute（file_url）;

public class MainActivity extends Activity {

    // Progress Dialog
    private ProgressDialog pDialog;
    public static final int progress_bar_type = 0;

    // File url to download
    private static String file_url = "http://www.qwikisoft.com/demo/ashade/20001.kml";

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        new DownloadFileFromURL().execute(file_url);

    }

    /**
     * Showing Dialog
     * */

    @Override
    protected Dialog onCreateDialog(int id) {
        switch (id) {
        case progress_bar_type: // we set this to 0
            pDialog = new ProgressDialog(this);
            pDialog.setMessage("Downloading file. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(true);
            pDialog.show();
            return pDialog;
        default:
            return null;
        }
    }

    /**
     * Background Async Task to download file
     * */
    class DownloadFileFromURL extends AsyncTask {

        /**
         * Before starting background thread Show Progress Bar Dialog
         * */
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            showDialog(progress_bar_type);
        }

        /**
         * Downloading file in background thread
         * */
        @Override
        protected String doInBackground(String... f_url) {
            int count;
            try {
                URL url = new URL(f_url[0]);
                URLConnection cOnection= url.openConnection();
                conection.connect();

                // this will be useful so that you can show a tipical 0-100%
                // progress bar
                int lenghtOfFile = conection.getContentLength();

                // download the file
                InputStream input = new BufferedInputStream(url.openStream(),
                        8192);

                // Output stream
                OutputStream output = new FileOutputStream(Environment
                        .getExternalStorageDirectory().toString()
                        + "/2011.kml");

                byte data[] = new byte[1024];

                long total = 0;

                while ((count = input.read(data)) != -1) {
                    total += count;
                    // publishing the progress....
                    // After this onProgressUpdate will be called
                    publishProgress("" + (int) ((total * 100) / lenghtOfFile));

                    // writing data to file
                    output.write(data, 0, count);
                }

                // flushing output
                output.flush();

                // closing streams
                output.close();
                input.close();

            } catch (Exception e) {
                Log.e("Error: ", e.getMessage());
            }

            return null;
        }

        /**
         * Updating progress bar
         * */
        protected void onProgressUpdate(String... progress) {
            // setting progress percentage
            pDialog.setProgress(Integer.parseInt(progress[0]));
        }

        /**
         * After completing background task Dismiss the progress dialog
         * **/
        @Override
        protected void onPostExecute(String file_url) {
            // dismiss the dialog after the file was downloaded
            dismissDialog(progress_bar_type);

        }

    }
}

10  

It is bad practice to perform network operations on the main thread, which is why you are seeing the NetworkOnMainThreadException. It is prevented by the policy. If you really must do it for testing, put the following in your OnCreate:

在主线程上执行网络操作是不好的做法，这就是您看到NetworkOnMainThreadException的原因。政策阻止了这一点。如果您真的必须进行测试，请将以下内容放入OnCreate中：

 StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
 StrictMode.setThreadPolicy(policy); 

Please remember that is is very bad practice to do this, and should ideally move your network code to an AsyncTask or a Thread.

请记住，执行此操作是非常糟糕的做法，理想情况下应将网络代码移动到AsyncTask或Thread。

1  

Mr.Iam4fun your code answer here..You will use thread...

Mr.Iam4fun你的代码在这里回答..你会用线程......

   findViewById(R.id.download).setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            new Thread(new Runnable() {
                public void run() {
                    DownloadFiles();
                }
            }).start();

And,then..

接着..

 public void DownloadFiles(){

        try {
            URL u = new URL("http://www.qwikisoft.com/demo/ashade/20001.kml");
            InputStream is = u.openStream();

            DataInputStream dis = new DataInputStream(is);

            byte[] buffer = new byte[1024];
            int length;

            FileOutputStream fos = new FileOutputStream(new File(Environment.getExternalStorageDirectory() + "/" + "data/test.kml"));
            while ((length = dis.read(buffer))>0) {
              fos.write(buffer, 0, length);
            }

          } catch (MalformedURLException mue) {
            Log.e("SYNC getUpdate", "malformed url error", mue);
          } catch (IOException ioe) {
            Log.e("SYNC getUpdate", "io error", ioe);
          } catch (SecurityException se) {
            Log.e("SYNC getUpdate", "security error", se);
          }
}
}

Sure, it will be working..

当然，它会工作..

1  

Simple kotlin version

简单的kotlin版本

fun download(link: String, path: String) {
    val input = URL(link).openStream()
    val output = FileOutputStream(File(path))
    input.use { _ ->
        output.use { _ ->
            input.copyTo(output)
        }
    }
}

0  

Run these codes in thread or AsyncTask. In order to avoid duplicated callings of same _url(one time for getContentLength(), one time of openStream()), use IOUtils.toByteArray of Apache.

在线程或AsyncTask中运行这些代码。为了避免重复调用相同的_url（一次为getContentLength（），一次为openStream（）），请使用Apache的IOUtils.toByteArray。

void downloadFile(String _url, String _name) {
    try {
        URL u = new URL(_url);
        DataInputStream stream = new DataInputStream(u.openStream());
        byte[] buffer = IOUtils.toByteArray(stream);
        FileOutputStream fos = mContext.openFileOutput(_name, Context.MODE_PRIVATE);
        fos.write(buffer);
        fos.flush();
        fos.close();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
        return;
    } catch (IOException e) {
        e.printStackTrace();
        return;
    }
}

0  

Apart from using AsyncTask you can put the operation in runnable-

除了使用AsyncTask之外，您还可以将操作置于runnable-

Runnable r=new Runnable()
{

public void run()
{
///-------network operation code
}
};

//--------call r in this way--
Thread t=new Thread(r);`enter code here`
t.start();

Also put the UI work in a haldler..such as updating a textview etc..

0  

Starting from api level 11 or Honeycomb doing network operations on main thread is forbidden. Use thread or asynctask. For more info visit https://developer.android.com/reference/android/os/NetworkOnMainThreadException.html

从api level 11或Honeycomb开始在主线程上进行网络操作是被禁止的。使用线程或asynctask。有关详细信息，请访问https://developer.android.com/reference/android/os/NetworkOnMainThreadException.html

0  

use AsyncTask and

使用AsyncTask和

put your download file code in doinbackground of it..

把你的下载文件代码放在它的doinbackground中..

android don't allow anymore to do heavy tasks on main thread to avoid ANR(Application not responding) error

android不再允许在主线程上执行繁重的任务以避免ANR（应用程序没有响应）错误

0  

I would recommend using Android DownloadManager

我建议使用Android DownloadManager

DownloadManager downloadmanager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
Uri uri = Uri.parse("http://www.example.com/myfile.mp3");

DownloadManager.Request request = new DownloadManager.Request(uri);
request.setTitle("My File");
request.setDescription("Downloading");
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setVisibleInDownloadsUi(false);
request.setDestinationUri(Uri.parse("file://" + folderName + "/myfile.mp3"));

downloadmanager.enqueue(request);

-1  

You should use an AsyncTask (or other way to perform a network operation on background).

您应该使用AsyncTask（或其他方式在后台执行网络操作）。

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //create and execute the download task
    MyAsyncTask async = new MyAsyncTask();
    async.execute();

}

private class MyAsyncTask extends AsyncTask{

    //execute on background (out of the UI thread)
    protected Long doInBackground(URL... urls) {
        DownloadFiles();
    }

}

More info about AsyncTask on Android documentation

有关Android文档中的AsyncTask的更多信息

Hope it helps.

希望能帮助到你。