当我尝试使用此代码时,它会开始下载,但随后警告“强制关闭” 我该怎么办?使用某种后台线程?
try {
long startTime = System.currentTimeMillis();
URL u = new URL("http://file.podfm.ru/3/33/332/3322/mp3/24785.mp3");
HttpURLConnection c = (HttpURLConnection) u.openConnection();
c.setRequestMethod("GET");
c.setDoOutput(true);
c.connect();
FileOutputStream f = new FileOutputStream(new File("/sdcard/","logo.mp3"));
InputStream in = c.getInputStream();
byte[] buffer = new byte[1024];
int len1 = 0;
while ( (len1 = in.read(buffer)) != -1 ) {
f.write(buffer,0, len1);
}
f.close();
Log.d("ImageManager", "download ready in" +
((System.currentTimeMillis() - startTime) / 1000) + " sec");
}
catch (IOException e)
{
Log.d("ImageManager", "Error" +
((System.currentTimeMillis()) / 1000) + e + " sec");
}
答案 0 :(得分:10)
我上周正在处理类似的问题,并最终使用显示进度条的AsyncTask
,因为可能需要一些时间来下载文件。一种方法是将下面的类嵌套在Activity
中,只需将它调用到您需要的位置即可:
new DownloadManager().execute("here be URL", "here be filename");
或者,如果课程不在活动中并且从活动中调用..
new DownloadManager(this).execute("URL", "filename");
这会传递活动,因此我们可以访问方法getSystemService();
这是执行所有脏工作的实际代码。您可能需要根据需要对其进行修改。
private class DownloadManager extends AsyncTask<String, Integer, Drawable>
{
private Drawable d;
private HttpURLConnection conn;
private InputStream stream; //to read
private ByteArrayOutputStream out; //to write
private Context mCtx;
private double fileSize;
private double downloaded; // number of bytes downloaded
private int status = DOWNLOADING; //status of current process
private ProgressDialog progressDialog;
private static final int MAX_BUFFER_SIZE = 1024; //1kb
private static final int DOWNLOADING = 0;
private static final int COMPLETE = 1;
public DownloadManager(Context ctx)
{
d = null;
conn = null;
fileSize = 0;
downloaded = 0;
status = DOWNLOADING;
mCtx = ctx;
}
public boolean isOnline()
{
try
{
ConnectivityManager cm = (ConnectivityManager)mCtx.getSystemService(Context.CONNECTIVITY_SERVICE);
return cm.getActiveNetworkInfo().isConnectedOrConnecting();
}
catch (Exception e)
{
return false;
}
}
@Override
protected Drawable doInBackground(String... url)
{
try
{
String filename = url[1];
if (isOnline())
{
conn = (HttpURLConnection) new URL(url[0]).openConnection();
fileSize = conn.getContentLength();
out = new ByteArrayOutputStream((int)fileSize);
conn.connect();
stream = conn.getInputStream();
// loop with step
while (status == DOWNLOADING)
{
byte buffer[];
if (fileSize - downloaded > MAX_BUFFER_SIZE)
{
buffer = new byte[MAX_BUFFER_SIZE];
}
else
{
buffer = new byte[(int) (fileSize - downloaded)];
}
int read = stream.read(buffer);
if (read == -1)
{
publishProgress(100);
break;
}
// writing to buffer
out.write(buffer, 0, read);
downloaded += read;
// update progress bar
publishProgress((int) ((downloaded / fileSize) * 100));
} // end of while
if (status == DOWNLOADING)
{
status = COMPLETE;
}
try
{
FileOutputStream fos = new FileOutputStream(filename);
fos.write(out.toByteArray());
fos.close();
}
catch ( IOException e )
{
e.printStackTrace();
return null;
}
d = Drawable.createFromStream((InputStream) new ByteArrayInputStream(out.toByteArray()), "filename");
return d;
} // end of if isOnline
else
{
return null;
}
}
catch (Exception e)
{
e.printStackTrace();
return null;
}// end of catch
} // end of class DownloadManager()
@Override
protected void onProgressUpdate(Integer... changed)
{
progressDialog.setProgress(changed[0]);
}
@Override
protected void onPreExecute()
{
progressDialog = new ProgressDialog(/*ShowContent.this*/); // your activity
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Downloading ...");
progressDialog.setCancelable(false);
progressDialog.show();
}
@Override
protected void onPostExecute(Drawable result)
{
progressDialog.dismiss();
// do something
}
}
答案 1 :(得分:2)
您应该尝试使用AsyncTask。你正在获得强制退出对话框,因为你试图在UI线程上做太多工作,并且Android判断你的应用程序没有响应。
this question的答案有一些很好的联系。
以下内容将是一个良好的开端:
private class DownloadLargeFileTask extends AsyncTask<Void, Void, Void> {
private final ProgressDialog dialog;
public DownloadLargeFileTask(ProgressDialog dialog) {
this.dialog = dialog;
}
protected void onPreExecute() {
dialog.show();
}
protected void doInBackground(Void... unused) {
downloadLargeFile();
}
protected void onPostExecute(Void unused) {
dialog.dismiss();
}
}
然后执行以下任务:
ProgressDialog dialog = new ProgressDialog(this);
dialog.setMessage("Loading. Please Wait...");
new DownloadLargeFileTask(dialog).execute();