public class Test extends Activity {    private Handler mHandler;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.front);        mHandler = new Handler();                /** 获取最后一次更新时间并保存到 Preferences 中 **/        SharedPreferences prefs = getPreferences(0);        lastUpdateTime =  prefs.getLong("lastUpdateTime", 0);                /** 查检是否更新 **/        if ((lastUpdateTime + (24 * 60 * 60 * 1000)) < System.currentTimeMillis()) {            /** 保存时间以便下次更新**/            lastUpdateTime = System.currentTimeMillis();                        SharedPreferences.Editor editor = getPreferences(0).edit();            editor.putLong("lastUpdateTime", lastUpdateTime);            editor.commit();                    /** 开始更新 **/                        checkUpdate.start();        }    }        /** 该线程在后台检查更新 **/    private Thread checkUpdate = new Thread() {        public void run() {            try {                URL updateURL = new URL("http://my.company.com/update");                                URLConnection conn = updateURL.openConnection();                 InputStream is = conn.getInputStream();                BufferedInputStream bis = new BufferedInputStream(is);                ByteArrayBuffer baf = new ByteArrayBuffer(50);                                int current = 0;                while((current = bis.read()) != -1){                     baf.append((byte)current);                }                /** 读取的字节转换为字符串. **/ final String s = new String(baf.toByteArray());                                         /** 获取当前版本号 **/                int curVersion = getPackageManager().getPackageInfo("your.app.id", 0).versionCode;                int newVersion = Integer.valueOf(s);                                /** 对比版本号? **/                if (newVersion > curVersion) {                    /** 显示更新 **/                    mHandler.post(showUpdate);                }                            } catch (Exception e) {            }        }    };    /** 该线打开市场下载应用 **/     private Runnable showUpdate = new Runnable(){           public void run(){            new AlertDialog.Builder(Test.this)            .setIcon(R.drawable.icon)            .setTitle("Update Available")            .setMessage("An update for is available!\\n\\nOpen Android Market and see the details?")            .setPositiveButton("Yes", new DialogInterface.OnClickListener() {                    public void onClick(DialogInterface dialog, int whichButton) {                            /** User clicked OK so do some stuff **/                            Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("market://search?q=pname:your.app.id"));                            startActivity(intent);                    }            })            .setNegativeButton("No", new DialogInterface.OnClickListener() {                    public void onClick(DialogInterface dialog, int whichButton) {                            /** User clicked Cancel **/                    }            })            .show();           }    };    }