自动更新版本

Android 应用自动更新代码
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); 
    } 
}