public class MainActivity extends Activity {
   private static final int PROCESSING = 1;
   private static final int FAILURE = -1;
   private EditText pathText;
   private TextView resultView;
   private Button downloadButton;
   private Button stopButton;
/**進度條*/
private ProgressBar progressBar;
   private 
 
Handler handler = new UIHandler();
/**
    * 當Handler被建立會關聯到建立它的當前執行緒的訊息佇列，該類用於往訊息佇列傳送訊息
    * 訊息佇列中的訊息由當前執行緒內部進行處理
    */
private final class UIHandler extends Handler {
      public void handleMessage(Message msg) {
         switch (msg.what) {
         case PROCESSING: //
progressBar.setProgress(msg.getData().getInt("size"
 
));
//已經下載的佔總的大小的百分比
float fraction = (float) progressBar.getProgress() / (float) progressBar.getMax();
//當前已經下載的大小
int currentLength = (int) (fraction * 100);
resultView.setText(currentLength + "%");
            if (progressBar.getProgress() == progressBar.getMax()) {
               Toast.makeText(getApplicationContext(), 
 
R.string.success, Toast.LENGTH_LONG).show();
}
            break;
         case FAILURE: // 下載失敗
Toast.makeText(getApplicationContext(), R.string.error, Toast.LENGTH_LONG).show();
            break;
}
      }
   }

   @Override
protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
setContentView(R.layout.main);
pathText = (EditText) findViewById(R.id.path);
resultView = (TextView) findViewById(R.id.resultView);
downloadButton = (Button) findViewById(R.id.downloadbutton);
stopButton = (Button) findViewById(R.id.stopbutton);
progressBar = (ProgressBar) findViewById(R.id.progressBar);
ButtonClickListener listener = new ButtonClickListener();
downloadButton.setOnClickListener(listener);
stopButton.setOnClickListener(listener);
pathText.setText("http://img3.iqilu.com/data/attachment/forum/201308/21/192654ai88zf6zaa60zddo.jpg");
}

   private final class ButtonClickListener implements View.OnClickListener {
      @Override
public void onClick(View v) {
         switch (v.getId()) {
         case R.id.downloadbutton: //開始下載
String path = pathText.getText().toString();
String filename = path.substring(path.lastIndexOf('/') + 1);
            try {
               filename = URLEncoder.encode(filename, "UTF-8");
} catch (UnsupportedEncodingException e) {
               e.printStackTrace();
}

            path = path.substring(0, path.lastIndexOf("/") + 1) + filename;
            if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
               File savDir = Environment.getExternalStorageDirectory();
download(path, savDir);
} else {
               Toast.makeText(getApplicationContext(), R.string.sdcarderror, Toast.LENGTH_LONG).show();
}
            downloadButton.setEnabled(false);
stopButton.setEnabled(true);
            break;
         case R.id.stopbutton: // 停止下載
exit();
Toast.makeText(getApplicationContext(), "Now thread is Stopping!!", Toast.LENGTH_LONG).show();
downloadButton.setEnabled(true);
stopButton.setEnabled(false);
            break;
}
      }


      private DownloadTask task;
      private void exit() {
         if (task != null)
            task.exit();
}

      private void download(String path, File savDir) {
         task = new DownloadTask(path, savDir);
         new Thread(task).start();
}

      private final class DownloadTask implements Runnable {
         private String path;
         private File saveDir;
         private FileDownloader loader;
         public DownloadTask(String path, File saveDir) {
            this.path = path;
            this.saveDir = saveDir;
}


         public void exit() {
            if (loader != null)
               loader.exit();
}

         DownloadProgressListener downloadProgressListener = new DownloadProgressListener() {
            @Override
public void onDownloadSize(int size) {
               Message msg = new Message();
msg.what = PROCESSING;
msg.getData().putInt("size", size);
handler.sendMessage(msg);
}
         };
@Override
public void run() {
            try {
               //構造下載器
loader = new FileDownloader(getApplicationContext(), path, saveDir, 3);
progressBar.setMax(loader.getFileSize());
//開始下載
loader.download(downloadProgressListener);
} catch (Exception e) {
               e.printStackTrace();
handler.sendMessage(handler.obtainMessage(FAILURE));
}
         }
      }
   }

}