Android 根据包名判断app是否安装

亲测可用：

public boolean isAppInstalled(Context context, String packageName) {          final PackageManager packageManager = context.getPackageManager();          List<PackageInfo> pinfo = packageManager.getInstalledPackages(0);          List<String> pName = new ArrayList<String>();          if (pinfo != null) {              for (int i = 0; i < pinfo.size(); i++) {                  String pn = pinfo.get(i).packageName;                  pName.add(pn);              }          }          return pName.contains(packageName);      }