问题
I am making an application in which I need to download a file from server and save it to sd card of android device.
Apart of this there is a feature for the user to pause and resume the file.
The problem I am facing is that I am able to download file to sdcard but when try to pause and resume it, it gets starts from the beginning.......
Here is the source ......
public class DownloadWithProgressActivity extends Activity {
public static final int DIALOG_DOWNLOAD_PROGRESS = 0;
private Button startBtn, pauseButton, resumeButton;
private ProgressBar bar;
URLConnection conexion;
OutputStream output;
static int count = 0;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
startBtn = (Button) findViewById(R.id.startBtn);
pauseButton = (Button) findViewById(R.id.button1);
resumeButton = (Button) findViewById(R.id.button2);
bar = (ProgressBar) findViewById(R.id.progressBar1);
bar.setVisibility(ProgressBar.INVISIBLE);
bar.setId(0);
startBtn.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
startDownload();
}
});
pauseButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
try {
output.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
resumeButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// not getting what to write here
}
});
}
private void startDownload() {
String url = "http://farm1.static.flickr.com/114/298125983_0e4bf66782_b.jpg";
new DownloadFileAsync().execute(url);
}
class DownloadFileAsync extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
bar.setVisibility(ProgressBar.VISIBLE);
}
@Override
protected String doInBackground(String... aurl) {
int downloaded = 0;
File file = new File("/sdcard/some_photo_from_gdansk_poland.jpg");
URL url = null;
try {
url = new URL(aurl[0]);
} catch (MalformedURLException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
conexion = url.openConnection();
if (file.exists()) {
downloaded = (int) file.length();
conexion.setRequestProperty("Range", "bytes="+(file.length())+"-");
}
else {
conexion.setRequestProperty("Range", "bytes=" + downloaded
+ "-");
}
} catch (Exception exception1) {
}
conexion.setDoInput(true);
conexion.setDoOutput(true);
System.out.println(tryGetFileSize(url));
conexion.setRequestProperty("Range", "bytes=" + count + "-");
try {
conexion.connect();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
int lenghtOfFile = conexion.getContentLength();
Log.d("ANDRO_ASYNC", "Lenght of file: " + lenghtOfFile);
InputStream input = null;
try {
input = new BufferedInputStream(url.openStream());
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
output = new FileOutputStream(file);
} catch (FileNotFoundException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
byte data[] = new byte[1024];
long total = 0;
try {
while ((count = input.read(data)) != -1) {
total += count;
publishProgress("" + (int) ((total * 100) / lenghtOfFile));
output.write(data, 0, count);
}
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
try {
output.flush();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
output.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
input.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
protected void onProgressUpdate(String... progress) {
Log.d("ANDRO_ASYNC", progress[0]);
bar.setProgress(Integer.parseInt(progress[0]));
System.out.println(Integer.parseInt(progress[0]));
}
protected void onPostExecute(String unused) {
}
int tryGetFileSize(URL url) {
HttpURLConnection conn = null;
try {
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("HEAD");
conn.getInputStream();
return conn.getContentLength();
} catch (IOException e) {
return -1;
} finally {
conn.disconnect();
}
}
}
}
Please help.......
Thanks Nikhil
回答1:
connection.setRequestProperty("Range", "bytes=" + ***downloaded*** + "-");
Make "downloaded" as global variable, because download start from this position.
when you press on restart button, check value of this downloaded variable,must not zero all time.
回答2:
This line return a wrong file size, I used the same code to open a Zip file on the net :
int lenghtOfFile = conexion.getContentLength();
How can I pause download other than by closing the output?
pauseButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
try {
output.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
});
resumeButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
// not getting what to write here
}
});
来源：https://stackoverflow.com/questions/7736307/android-pause-and-resume-downloading-file-to-sdcard