android获取版本号

要写到onCreate()里，setContentView()之后才能用

String appVersion;
PackageManager manager = this.getPackageManager();
        try {	PackageInfo info = manager.getPackageInfo(this.getPackageName(), 0);
        		appVersion = info.versionName;   //版本名
        		} catch (NameNotFoundException e) {
        			// TODO Auto-generated catch block
        			e.printStackTrace();
        		}