进度条更新进度

Question

我想在文件加密时运行ProgressBar。

我有以下代码，但是如何知道或分解大小，以便在完成时达到100％？正如在更新加密工作时的进度栏％。

我是新来的Android，所以我有一些我仍然不知道，理解的东西。

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; 
} 

}

Answer 1

你知道纯文本的大小，所以，如果你正在写的CipherOutputStream，只是换一个带有CountingOutputStream。您可以对CipherInputStream执行相同操作，但当然也可以执行CountingInputStream。在这种情况下，您最好将CountingInputStream置于CipherInputStream之内，因为您可能事先知道密文大小，而不是纯文本。你可能不在乎，因为纯文本和密文的大小几乎相同 - 用户不应该看到太大的差别。这两个类都可以在Apache commons I/O库中找到。

当然，如果你事先知道明文/密文的大小，当然会有所帮助，但我想这是说明问题。文件的大小可以找到through the standard java.nio libraries或the older Java 6 new I/O API。最后，在写入流之前，你显然不应该首先将所有的字节流到内存中，例如，改为4KiB块大小（如果可能，使用ByteBuffer）。

Answer 2

看一看的AsyncTask http://developer.android.com/reference/android/os/AsyncTask.html 它会做你想要什么 - 不是试图使用原始线程更容易了很多。