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);   
    }   
  
}