Progress Bar Update Progress

问题

I would like to have a ProgressBar running while the file is being encrypt.

I have the following code, but how can I know or break down the size, so that when it is done it reaches 100%? As in, updating the progress bar % while the encryption is working.

I'm new to Android, so I have quite a bit of things I still do not know, understand yet.

import java.io.File;

public class ProgressBarExa extends Activity {

Button btnStartProgress;
ProgressDialog progressBar;
private int progressBarStatus = 0;
private Handler progressBarHandler = new Handler();

// private long fileSize = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.progressbar_view);

    addListenerOnButton();

}

public void addListenerOnButton() {

    btnStartProgress = (Button) findViewById(R.id.btnStartProgress);
    btnStartProgress.setOnClickListener(
             new OnClickListener() {

       @Override
       public void onClick(View v) {

        // prepare for a progress bar dialog
        progressBar = new ProgressDialog(v.getContext());
        progressBar.setCancelable(true);
        progressBar.setMessage("File encrypting...");
        progressBar.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        progressBar.setProgress(0);
        progressBar.setMax(100);
        progressBar.show();

        //reset progress bar status
        progressBarStatus = 0;

        //reset filesize
        // fileSize = 0;

        new Thread(new Runnable() {
          public void run() {
            while (progressBarStatus < 100) {

              // process some tasks
              progressBarStatus = doSomeTasks();

              // your computer is too fast, sleep 1 second
              try {
                Thread.sleep(1000);
              } catch (InterruptedException e) {
                e.printStackTrace();
              }

              // Update the progress bar
              progressBarHandler.post(new Runnable() {
                public void run() {
                  progressBar.setProgress(progressBarStatus);
                }
              });
            }

            // ok, file is downloaded,
            if (progressBarStatus >= 100) {

                // sleep 2 seconds, so that you can see the 100%
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                // close the progress bar dialog
                progressBar.dismiss();
            }
          }
           }).start();

           }

            });

    }

// file download simulator... a really simple
public int doSomeTasks() {

    try{
        String baseDir = Environment.getExternalStorageDirectory().getAbsolutePath();
        String fileName = "a.wmv";
        String newFileNEE = "b.wmv";
        String newFileNED = "c.wmv";

        FileInputStream fis = new FileInputStream(new File(baseDir + File.separator + fileName));

        File outfile = new File(baseDir + File.separator + newFileNEE);
            int read;
            if(!outfile.exists())
                outfile.createNewFile();

            // long outfile_size = outfile.length();

            File decfile = new File(baseDir + File.separator + newFileNED);
            if(!decfile.exists())
                decfile.createNewFile();


            FileOutputStream fos = new FileOutputStream(outfile);
            FileInputStream encfis = new FileInputStream(outfile);
            FileOutputStream decfos = new FileOutputStream(decfile);

            Cipher encipher = Cipher.getInstance("AES");
            Cipher decipher = Cipher.getInstance("AES");

            KeyGenerator kgen = KeyGenerator.getInstance("AES");
            SecretKey skey = kgen.generateKey();
            encipher.init(Cipher.ENCRYPT_MODE, skey);
            CipherInputStream cis = new CipherInputStream(fis, encipher);
            decipher.init(Cipher.DECRYPT_MODE, skey);
            CipherOutputStream cos = new CipherOutputStream(decfos,decipher);

            while((read = cis.read())!=-1)
                    {
                        fos.write((char)read);
                        fos.flush();
                    }   
            fos.close();
            while((read=encfis.read())!=-1)
            {
                cos.write(read);
                cos.flush();
            }
            cos.close();

    }catch (Exception e) {
        // TODO: handle exceptione
        e.printStackTrace();
    }
    return 100;
}

}

回答1:

Take a look at AsyncTask http://developer.android.com/reference/android/os/AsyncTask.html It will do exactly what you want -- a lot easier than trying to use a raw Thread.

回答2:

You know the size of the plain text, so if you are writing to the CipherOutputStream, simply wrap that one with a CountingOutputStream. You can do the same for the CipherInputStream, but with a CountingInputStream of course. In that case you are better off putting the CountingInputStream within the CipherInputStream as you probably know the ciphertext size in advance, not the plain text. You may not care though, as the plain text and cipher text should be almost identical in size - a user should not see much difference. Both classes can be found in the Apache commons I/O libraries.

It of course helps if you know the size of the plaintext / ciphertext in advance, but I guess that speaks for itself. The size of files can be found through the standard java.nio libraries or the older Java 6 new I/O API. Finally, you should obviously not first stream all the bytes to memory before writing it to the streams, use e.g. 4KiB block sizes instead (using ByteBuffer if possible).

来源：https://stackoverflow.com/questions/15508784/progress-bar-update-progress