返回从通知栏下载活动

Question

我知道关于这个主题有很多问题，但没有人能回答我的具体问题，或者也许我无论如何都无法识别正确的答案！

就像Android Market下载一个文件时，Activity中有进度条，通知栏有进度条一样，点击通知进度条返回到原来的Activity，进度条会随着下载进度而更新。

我正在使用 AsyncTask 进行下载和创建&更新通知栏一切正常，但是当我单击通知时，它返回到相同的活动，但没有任何数据或进度条（空白活动），换句话说，它启动新活动并丢失额外内容和所有字段数据，包括活动进度条状态。

我尝试使用标志和意图，但在单击通知栏时未能加载原始活动，特别是在返回另一个活动然后转到主屏幕然后按通知栏时。

我通过以下方式运行下载：

df = new AsyncDownloadTask();
df.execute(m_item.getiid(),m_item.getipackage());

和代码片段（我更改了通知栏只是为了显示进度文本）：

protected void onCreate(Bundle savedInstanceState) 
{
super.onCreate(savedInstanceState);
setContentView (R.layout.activity_app_display);
//get extras
Bundle extras = getIntent().getExtras();

    if (extras == null) {
        return;
    }
    itemId = extras.getString("id");
    itemStatus = extras.getString("IorU");
    ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressbar);
    progressBar.setVisibility(0);

   showUI();

}
private void showUI() {

if(m_item != null) { 

    TextView actvTitle = (TextView) findViewById(R.id.title_text);
    actvTitle.setText(m_item.geticategory());

    appinstall = (Button) findViewById(R.id.app_install_btn);
    appudinstall = (Button) findViewById(R.id.app_udinstall_btn);

    permlist = (LinearLayout) findViewById(R.id.app_perm); //
    info = (LinearLayout) findViewById(R.id.info);
    mList = (HeightListView) findViewById(R.id.app_perm_list);
    mList.setTextFilterEnabled(true);


    instTxt = (TextView) findViewById(R.id.app_install);

    TextView titleTxt = (TextView) findViewById(R.id.app_titlebig);
    TextView companyTxt = (TextView) findViewById(R.id.app_descbig);

    TextView descTxt = (TextView) findViewById(R.id.long_desc);
    TextView verTxt = (TextView) findViewById(R.id.version);

    //fill info
    titleTxt.setText(m_item.getititle());
    companyTxt.setText(m_item.geticompany());
    descTxt.setText(m_item.getidescription());
    verTxt.setText(" Version:" + m_item.getiversion());


}
   }

@Override
protected void onResume(){
super.onResume();
}

@Override
public Object onRetainNonConfigurationInstance() {
Toast.makeText (getApplicationContext(), "onRetainNonConfigurationInstance", Toast.LENGTH_SHORT).show();
return null;
}
@Override
protected void onDestroy() {
super.onDestroy();
/*
if(df != null)
{
  if(!df.isCancelled())
    df.cancel(true);
}
CN=true;
*/

}
@Override
protected void onPause() {
super.onPause();
}
@Override
protected void onStart() {
super.onStart(); 
}



private class AsyncDownloadTask extends AsyncTask<String, Integer, Void>
   {
  private int successCount;
  private int numTotalFiles;
  private File outputFile;
  private String pack;
  private int downloadErr = 0;


  @Override
  protected void onPreExecute()
  {
super.onPreExecute();

successCount = 0;
notificationManager = (NotificationManager) getApplicationContext().getSystemService(getApplicationContext().NOTIFICATION_SERVICE);
CN=false;
  }


  @Override
  protected Void doInBackground(String... params)
  {
    String remoteFilepath;
String id = params[0];
pack = params[1];
  remoteFilepath = "http://www.myserver/download/1.zip";

  String PATH = Environment.getExternalStorageDirectory()+ "/download/";
  File file = new File(PATH);
  file.mkdirs();
  try
  {
    if(isCancelled())
      return null;

    URL url = new URL(remoteFilepath);
    HttpURLConnection c = (HttpURLConnection) url.openConnection();
    c.setConnectTimeout(getConnectTimeout());
    c.setReadTimeout(getReadTimeout());
    c.setRequestMethod("GET");
    c.setDoOutput(true);
    c.connect();
    int filesize = c.getContentLength();
    if(filesize > 0)
    {

      outputFile = new File(file, "1.zip");
      FileOutputStream fos = new FileOutputStream(outputFile);

      InputStream is = c.getInputStream();
      int bytesRead, totalBytesRead = 0;
      byte[] bytes = new byte[BYTES_BUFFER_SIZE];
      String progress, kbytes;
      while(!isCancelled() && (bytesRead = is.read(bytes)) != -1)
      {
        totalBytesRead += bytesRead;
        fos.write(bytes, 0, bytesRead);
        if(!isCancelled() ) //&& loopCount++ % 20 == 0)
        {
          RemoteViews progressView = getProgressView(successCount + 1, numTotalFiles, totalBytesRead, filesize);
          if(progressView == null)
          {
            progress = "Download "+pack;
            kbytes = String.format("%s / %s", getStringByteSize(totalBytesRead), getStringByteSize(filesize));

            if(!isCancelled() && !CN){
              showNotification("Downloading File(s)", progress , kbytes);
              publishProgress(totalBytesRead,filesize);
            } else { return null; }
          }
          else
          {

            if(!isCancelled() && !CN){
              showNotification(progressView, "Downloading File(s)");
            } else { return null; }
          }

        }
      }
      fos.close();
      is.close();
      if(isCancelled())
        return null;

      successCount ++;
    }
    else
    {
    }
  }
  catch(Exception e)
  {
      e.printStackTrace();
    showNotification("Download Failed", "Download Progress", "Failed: " + (new File(remoteFilepath)).getName());
    //updateCancelInstall();
    publishProgress(100,100);
    notificationManager.cancel(42);
    downloadErr = 1;
    CN = true;
  }

return null;
  }

  @Override
  protected void onCancelled()
  {
super.onCancelled();
showNotification("Download Cancelled", "Download Progress", "Cancelled");
CN = true;
publishProgress(100,100);
notificationManager.cancel(42);
  }

  protected void onProgressUpdate(Integer... prog) {
  if(prog[0]<prog[1]){
      updateProgress(prog[0],prog[1],false);
  } else {
      updateProgress(100,100,true);
      notificationManager.cancel(42);
  }
  }


  @Override
 protected void onPostExecute(Void result)
 {
super.onPostExecute(result);
if(!CN){
    if(downloadErr==0) {
        showNotification("Installing", "Installing "+pack, "Completed");
        updateDLcount udl = new updateDLcount();
        udl.execute("hello"); 
        //updateCancelInstall();
        notificationManager.cancel(42);
    } else {

        showNotification("Download Error", "Failed to download "+pack, "Error");
        //updateCancelInstall();
        notificationManager.cancel(42);
       }
   }
 }
}

   protected RemoteViews getProgressView(int currentNumFile, int totalNumFiles, int  currentReceivedBytes, int totalNumBytes)
  {
    return null;
  }



   protected Class<?> getIntentForLatestInfo()
   {
 return DisplayApp.class;
   }

protected void showNotification(String ticker, String title, String content)
{

  Notification notification = new Notification(R.drawable.download_icon, ticker, System.currentTimeMillis());
  Intent i=new Intent(this, DisplayApp.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP);
i.putExtra("id", itemId);
i.putExtra("IorU", "itemStatus");
i.putExtra("progrss", content);
  PendingIntent contentIntent = PendingIntent.getActivity(this, 0, i, 0);
  notification.setLatestEventInfo(getApplicationContext(), title, content, contentIntent);
  notification.flags = notification.flags | Notification.FLAG_ONGOING_EVENT;

  notificationManager.notify(42, notification);
if(content.equalsIgnoreCase("Cancelled")||content.equalsIgnoreCase("Completed")||CN)notificationManager.cancel(42);
}
protected void updateProgress(int downsize, int totalsize, boolean cancel){

//Log.i("YYYY","cancel="+cancel);

if(!cancel || (downsize<totalsize)){
    ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressbar);
    TextView pb_t = (TextView) findViewById(R.id.progressbar_text);
    progressBar.setVisibility(0);
    pb_t.setVisibility(0);
    progressBar.setProgress((int)downsize*100/totalsize);
    pb_t.setText(String.format("%s / %s", getStringByteSize(downsize), getStringByteSize(totalsize)));
} else {
    ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressbar);
    TextView pb_t = (TextView) findViewById(R.id.progressbar_text);
    progressBar.setProgress(100);
    progressBar.setVisibility(4);
    pb_t.setVisibility(4);
    updateCancelInstall();
} 
}


protected void showNotification(RemoteViews remoteView, String ticker)
{
  Notification notification = new Notification(R.drawable.download_icon, ticker, System.currentTimeMillis());
  notification.contentView = remoteView;
  Intent i=new Intent(this, DisplayApp.class);
i.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP);
  notification.contentIntent = PendingIntent.getActivity(this, 0, i, 0);
  //Log.d("YYYY","2:"+notification.contentIntent.toString());
  notification.flags = notification.flags | Notification.FLAG_ONGOING_EVENT;

  notificationManager.notify(42, notification);
}

如果您可以通过代码、网址或任何模仿市场方式的文档来帮助我，我们将不胜感激。

谢谢

Answer 1

我在 Activity 的 launchMode 中使用了 singleInstance，该 Activity 出现在前面，进度条随着下载的进行而进行。

我发现只有当我返回然后回家然后单击通知栏时才会感到困惑，这一点很明显，因为单击返回会破坏我的活动并且我会丢失历史记录，所以我的解决方法是禁用我的活动中的后退键并让应用程序用户浏览我的 UI 菜单和按钮。

我知道应该有办法存储我的活动实例并在以后检索它，无论历史记录/堆栈发生什么，但到目前为止，上面的内容对我来说已经足够了！

谢谢，

Answer 2

在您的 AndroidManifest.xml 文件中，尝试在您希望返回的 Activity 下添加 android:launchMode="singleTop" 行。例如：

这将阻止创建 Activity 的新实例，并将 Intent 路由到 Activity 的任何当前实例。有关详细信息，请参阅此处。