判断Android应用程序是否已安装

     <span style="line-height:20px;font-size:14px;-webkit-border-horizontal-spacing:2px;-webkit-border-vertical-spacing:2px;">android应用程序是否已安装,查看是否此包的相关信息</span>    <br />    <span style="font-family:Arial;color:#625b49;"><span style="line-height:20px;font-size:14px;-webkit-border-horizontal-spacing:2px;-webkit-border-vertical-spacing:2px;"><pre class="brush:java; toolbar: true; auto-links: false;">  PackageInfo packageInfo;          try {             packageInfo = this.getPackageManager().getPackageInfo(                     packagename, 0);          } catch (NameNotFoundException e) {             packageInfo = null;             e.printStackTrace();         }         if(packageInfo ==null){             System.out.println("not installed");         }else{             System.out.println("is installed");         }</pre></span></span>