Android 自动更新代码

import java.io.File;  import java.io.FileOutputStream;import java.io.IOException;  import java.io.InputStream;  import org.apache.http.HttpEntity;  import org.apache.http.HttpResponse;  import org.apache.http.client.ClientProtocolException;  import org.apache.http.client.HttpClient;  import org.apache.http.client.methods.HttpGet;  import org.apache.http.impl.client.DefaultHttpClient;    import android.app.AlertDialog;  import android.app.Dialog;  import android.app.ProgressDialog;  import android.content.DialogInterface;  import android.content.Intent;  import android.net.Uri;  import android.os.Bundle;  import android.os.Environment;  import android.os.Handler;    public class Update extends BaseActivity {      public ProgressDialog pBar;      private Handler handler = new Handler();        @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.update);          Dialog dialog = new AlertDialog.Builder(Update.this).setTitle("系统更新")                  .setMessage("发现新版本，请更新！")// 设置内容                  .setPositiveButton("确定",// 设置确定按钮                          new DialogInterface.OnClickListener() {                                @Override                              public void onClick(DialogInterface dialog,                                      int which) {                                  pBar = new ProgressDialog(Update.this);                                  pBar.setTitle("正在下载");                                  pBar.setMessage("请稍候...");                                  pBar                                          .setProgressStyle(ProgressDialog.STYLE_SPINNER);                                  downFile("http://url:8765/OA.apk");                                                                  }                            }).setNegativeButton("取消",                            new DialogInterface.OnClickListener() {                              public void onClick(DialogInterface dialog,                                      int whichButton) {                                  // 点击"取消"按钮之后退出程序                                                                }                          }).create();// 创建          // 显示对话框          dialog.show();        }        void downFile(final String url) {          pBar.show();          new Thread() {              public void run() {                  HttpClient client = new DefaultHttpClient();                  // params[0]代表连接的url                  HttpGet get = new HttpGet(url);                  HttpResponse response;                  try {                      response = client.execute(get);                      HttpEntity entity = response.getEntity();                      long length = entity.getContentLength();                      InputStream is = entity.getContent();                      FileOutputStream fileOutputStream = null;                      if (is != null) {                            File file = new File(Environment                                  .getExternalStorageDirectory(), "OA.apk");                          fileOutputStream = new FileOutputStream(file);                                                    byte[] buf = new byte[1024];                          int ch = -1;                          int count = 0;                          while ((ch = is.read(buf)) != -1) {                              // baos.write(buf, 0, ch);                              fileOutputStream.write(buf, 0, ch);                              count += ch;                              if (length > 0) {                                                            }                            }                        }                      fileOutputStream.flush();                      if (fileOutputStream != null) {                          fileOutputStream.close();                      }                      down();                  } catch (ClientProtocolException e) {                      // TODO Auto-generated catch block                      e.printStackTrace();                  } catch (IOException e) {                      // TODO Auto-generated catch block                      e.printStackTrace();                  }              }            }.start();        }        void down() {          handler.post(new Runnable() {              public void run() {                  pBar.cancel();                  update();              }          });        }        void update() {            Intent intent = new Intent(Intent.ACTION_VIEW);          intent.setDataAndType(Uri.fromFile(new File("/sdcard/OA.apk")),                  "application/vnd.android.package-archive");          startActivity(intent);      }    }