android应用客户端自动升级

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); 
     } 
  
}