根据包名判断app是否安装

在app判断手机里面某个app是否安装，前提是要知道要判断点app的包名，像微信这类应用，百度一下就知道包名了

private boolean isAppInstalled(Context context, String packagename) {
PackageManager pm = context.getPackageManager();
 boolean installed = false;
  try {
      pm.getPackageInfo(packagename, PackageManager.GET_ACTIVITIES);
      installed = true;
     } catch (PackageManager.NameNotFoundException e) {
    installed = false;
}
 return installed;
}