Android如何判断应用程序是否安装

通过包名进行判断，代码如下：

/*
* check the app is installed
*/
private boolean isAppInstalled(Context context,String packagename)
{
PackageInfo packageInfo;        
try {
            packageInfo = context.getPackageManager().getPackageInfo(packagename, 0);
         }catch (NameNotFoundException e) {
            packageInfo = null;
            e.printStackTrace();
         }
         if(packageInfo ==null){
            //System.out.println("没有安装");
            return false;
         }else{
            //System.out.println("已经安装");
            return true;
        }
}