Android Multi-threaded Downloads

Project Source Download

Https://github.com/Wang-Jun-Chao/AndroidProjects

Multi-Threaded Download

Principle: Server CPU allocated to each thread of the same time slice, the server bandwidth evenly allocated to each thread, so the more threads the client opens, you can preempt more server resources

Determine how much data each thread downloads

Send HTTP request to download address

        String path = 
        url url = new URL (path)
        httpurlconnection conn = (httpurlconnection) URL ()
        conn ()
        Conn () C8/>conn ()

Gets the total length of the file, and then creates a consistent, temporary file

        (Conn.getresponsecode () = =) {
            
             length = Conn.getcontentlength ();
            
            Randomaccessfile RAF =  randomaccessfile (getfilename (path));
            
            Raf.setlength (length);
            Raf. ();

Determine how much data the thread downloads

            
             BlockSize =  /thread_count;

Calculates the starting and ending positions of each thread's downloaded data

        (  = ;  <=; + +) {
            
             StartIndex = (-) * blockSize;
             Endindex =  * blockSize-;
            (= = Thread_count) {
                endindex = length;
            }

            
            New Downloadthread (StartIndex, Endindex,) ();
        }

Send the request to the download address again, the request start position to the end position data

        String path =;

        URL url =  url (path);
        HttpURLConnection conn = (httpurlconnection) url.openconnection ();
        Conn.setreadtimeout);
        Conn.setconnecttimeout);
        Conn.setrequestmethod ();

        
        Conn.setrequestproperty (,  + startIndex + +  endindex);
        Conn.connect ();
* Download the requested data and store it in the temporary file

        (conn.getresponsecode () = =) {
            InputStream is = Conn.getinputstream ();
            Randomaccessfile RAF =  randomaccessfile (getfilename (path));
            
            Raf.seek (startIndex);
            [] b =  ];
             ;
            while (= Is.read (b))!=) {
                raf.write (b,,);
            }
            Raf. ();
        }

Multi-threaded Download with breakpoint continuation

Define an int variable to record the total length of the data downloaded by each thread, then add the thread's download start position, and the result is the start of the thread at the next download, and the resulting result is stored in the cached file.

        
         Total =;
        while (= Is.read (b))!=) {
            raf.write (b,,);
            Total + =;
            
            Randomaccessfile raf2 =  randomaccessfile (threadId +,);
            Raf2.write ((StartIndex + total +). GetBytes ());
            Raf2. ();
        }

The next time the download starts, read the value in the cached file, and the resulting value is the starting position of the line threading.

        FileInputStream FIS =  fileinputstream ();
        BufferedReader br =  bufferedreader (inputstreamreader (FIS));
         Text = Br.readline ();
        int newstartindex =. parseint (text);
        Read the value as a new starting position
        StartIndex = Newstartindex;
        Fis.close ();

After all three threads have been downloaded, delete the cached file

        running_thread--;
        (Running_thread = =) {
            (i =; I <=; i++) {
                file F =  file (i +);
                F. ();
            }
        

Mobile version of the breakpoint continued to pass the multithread download device

Just paste the code directly over it, and remember to change the path to the Android directory when accessing the file, adding access to the network and external storage

Show download progress with progress bar

When you get the total length of the download file, set the maximum value of the progress bar

        
        Pb.setmax ();

The progress bar needs to display three threads of the overall download progress, so three threads per download, the new download length will be added to the progress bar

Defines an int global variable that records the total download length of three threads

             Progress

* Refresh progress bar
  

            while (= Is.read (b))!=) {
                raf.write (b,,);

                
                Progress + =;
                Pb.setprogress (progress);

Every time the breakpoint is downloaded, the new start is downloaded, and the progress bar is displayed from the new location, and the progress bar progress is also processed when the cache file is fetched for the newly downloaded start position.

        FileInputStream FIS =  fileinputstream (file);
        BufferedReader br =  bufferedreader (inputstreamreader (FIS));
        String text = Br.readline ();
         Newstartindex = Integer.parseint (text);

        
         Alreadydownload = Newstartindex-startindex;
        
        Progress + = Alreadydownload;

Add a text box to show percent progress

        TV (Progress *  /PB () +)

The use of Httputils

Httputils itself supports multi-threaded breakpoint continuation, it is very convenient to use

Creating Httputils Objects

=

Download files

        Http.download (URL, 
                target,,, 
                 requestcallback<file> () {

            
            
              responseinfo<file> arg0) {
                Tv.settext (+ Arg0.result.getPath ());
            }

            
            
              (HttpException arg0, String arg1) {
                Tv.settext (+ arg1);
            }

            
            
              (Total, current  ,  isuploading) {
                . onloading (Total, Current, isuploading);
                
                Pb.setmax (() total);
                
                Pb.setprogress (() current);
                Tv_progress.settext (Current *  /Total +);
            }
        });

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