利用Android如何实现一个判断手机是否安装了QQ或微信的功能

public static boolean isWeixinAvilible(Context context) { 
    final PackageManager packageManager = context.getPackageManager();// 获取packagemanager 
    List<PackageInfo> pinfo = packageManager.getInstalledPackages(0);// 获取所有已安装程序的包信息 
    if (pinfo != null) { 
      for (int i = 0; i < pinfo.size(); i++) { 
        String pn = pinfo.get(i).packageName; 
        if (pn.equals("com.tencent.mm")) { 
          return true; 
        } 
      } 
    } 
    return false; 
  } 
  /** 
   * 判断qq是否可用 
   *  
   * @param context 
   * @return 
   */ 
  public static boolean isQQClientAvailable(Context context) { 
    final PackageManager packageManager = context.getPackageManager(); 
    List<PackageInfo> pinfo = packageManager.getInstalledPackages(0); 
    if (pinfo != null) { 
      for (int i = 0; i < pinfo.size(); i++) { 
        String pn = pinfo.get(i).packageName; 
        if (pn.equals("com.tencent.mobileqq")) { 
          return true; 
        } 
      } 
    } 
    return false; 
  }