if turn off wifi,cancel download [android]

Question

in the following code I used of onpause and onstop and ondestroy but it is useless and when turn off wifi by user save incomplete file but I want when turn off wifi by user,canceled download.

what can i do?

what should I add in the code?

my code:

 public class DoaMatn1 extends Activity implements OnClickListener {
//           .
//           .
//           .
  @Override
    protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.doamatn);
//           .
//           .
//           .
}
Intent intent = new Intent(android.content.Intent.ACTION_VIEW);
File sdcard = Environment.getExternalStorageDirectory();
File audioFile = new File(sdcard.getPath() + "/EBKH/basem-tavasol.mp3");
@Override
public void onClick(View v) {
    switch(v.getId())
    {
    case R.id.btnplaydoa :
//           .
//           .
//           .
    case R.id.btndowndoa :
        if(!new File(Environment.getExternalStorageDirectory().toString() + "/EBKH/basem-tavasol.mp3").exists())          
            downloadTask = (DownloadFileFromURL) new DownloadFileFromURL().execute(file_url);
}}
@Override
protected void onStop() {
    if(downloadTask!=null){
        downloadTask.cancel(true);
    }
    super.onStop();
}
@Override
protected void onPause() {
if(downloadTask!=null){
    downloadTask.cancel(true);
 }
super.onPause();
 }
 @Override
 protected void onDestroy() {
if(downloadTask!=null){
    downloadTask.cancel(true);
 }
super.onDestroy();
 }
 class DownloadFileFromURL extends AsyncTask<String, String, String> {
@Override
protected void onCancelled() {
    File file= new File("/sdcard/EBKH/basem-tavasol.mp3");
    file.delete();
}
@Override
protected void onPreExecute() {
    super.onPreExecute();
    showDialog(progress_bar_type);
}
@Override
protected String doInBackground(String... f_url) {
    int count;
    try {
        URL url = new URL(f_url[0]);
        URLConnection conection = url.openConnection();
        conection.connect();
        int lenghtOfFile = conection.getContentLength();
        InputStream input = new BufferedInputStream(url.openStream(), 8192);
        OutputStream output = new FileOutputStream("/sdcard/EBKH/basem-tavasol.mp3");
        byte data[] = new byte[1024];
        long total = 0;
        while ((count = input.read(data)) != -1) {
            total += count;
            publishProgress(""+(int)((total*100)/lenghtOfFile));
            output.write(data, 0, count);
        }
        output.flush();
        output.close();
        input.close();
    } catch (Exception e) {
        Log.e("Error: ", e.getMessage());
    }
    return null;
}
protected void onProgressUpdate(String... progress) {

    pDialog.setProgress(Integer.parseInt(progress[0]));
}
@Override
protected void onPostExecute(String file_url) {


    dismissDialog(progress_bar_type);
 }}

Answer 1

Taken from this question...

Register a broadcast receiver:

IntentFilter intentFilter = new IntentFilter();
intentFilter.addAction(WifiManager.NETWORK_STATE_CHANGED_ACTION);
registerReceiver(broadcastReceiver, intentFilter);

and receive:

@Override
public void onReceive(Context context, Intent intent) {

    final String action = intent.getAction();

    if(action.equals(WifiManager.NETWORK_STATE_CHANGED_ACTION)){
        NetworkInfo info = intent.getParcelableExtra(WifiManager.EXTRA_NETWORK_INFO);
        boolean connected = info.isConnected();
        if (!connected) {
            // Stop the download.
        }
    }      
} 

This method will detect a change in wifi and if the change is that the wifi is not connected, cancel the download.