I want to download a file programically in android but when run,it closed?

Question

I think my connection failed but I cant Repair code.

URL url = new URL( imageURL);
File file = new File(fileName);
URLConnection ucon = url.openConnection();
InputStream is = ucon.getInputStream();
BufferedInputStream bis = new BufferedInputStream(is);

when debug it crashed in this part of code. I use

<uses-permission android:name="android.permission.INTERNET"/>

and

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

check my related post: http://stackoverflow.com/questions/15549421/how-to-download-and-save-an-image-in-android/15549639#15549639 — Droidman, Feb 25 '14 at 07:46
I think your logcat contains `NetworkOnMainThreadException`. To be sure, copy the error from your logcat — Glenn, Feb 25 '14 at 07:54
execute this in Asynctask or a thread. You must be executing it on your main UIthread like onCreate() — Sheraz Ahmad Khilji, Feb 25 '14 at 08:06
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195) — mohammad madani, Feb 25 '14 at 08:13

score 2 · Accepted Answer · answered Feb 26 '14 at 12:15

Write below code into your MainActivity after setContentView(R.layout.activity_main)

 if (android.os.Build.VERSION.SDK_INT > 9) {
        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder().permitAll().build();
        StrictMode.setThreadPolicy(policy);
    }

score 0 · Answer 2 · edited May 23 '17 at 11:52

Above android 3.0 you need to do all your networking in a seperate thread. So if you try that code in the main thred it will throw a NetworkOnMainThread exception.

try this to verify it:

try{
    URL url = new URL( imageURL);
    File file = new File(fileName);
    URLConnection ucon = url.openConnection();
    InputStream is = ucon.getInputStream();
    BufferedInputStream bis = new BufferedInputStream(is);
}
catch (android.os.NetworkOnMainThreadException ex){
    // Skipp.
}

If your app doesn't crashes this way then you need to use an AssyncTask for the networking. Here is a good examplehow to .

And don't forget to check your filepath as well like @LucianNovac suggests.

Lucian Novac · Answer 3 · 2014-02-25T08:00:35.057

Try to initialize the file like this:

File extStore = Environment.getExternalStorageDirectory();
File file = new File(extStore, fileName);

and don't forget to put in your manifest file

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

Also to avoid Network exception put this into an asynk

class DownloadMyFIle extends AsyncTask<String, Void, DownloadProcess> {

    private Exception exception;

    protected DownloadProcess doInBackground(String... urls) {
        try {
            File extStore = Environment.getExternalStorageDirectory();
            File file = new File(extStore, fileName);
            ....
        } catch (Exception e) {
            this.exception = e;
            return null;
        }
    }

    protected void onPostExecute(DownloadProcess process) {
        // TODO: check this.exception 

    }
}

I want to download a file programically in android but when run,it closed?

3 Answers3