Question

widgets库捕获了一个异常，不确定是怎么回事。这里的“未来”构建器似乎有点问题。是否缺少像ELSE子句之类的东西？请指导。代码：

buildProfileHeader() {
    return FutureBuilder(
      future: usersRef.document(widget.profileId).get(),
      builder: (context, snapshot) {
        if (!snapshot.hasData) {
          return circularProgress();
        }
        User user = User.fromDocument(snapshot.data);
        return Padding(
          padding: EdgeInsets.all(16.0),
          child: Column(
            children: <Widget>[
              Row(
                children: <Widget>[
                  CircleAvatar(
                    radius: 40.0,
                    backgroundColor: Colors.grey,
                    backgroundImage: CachedNetworkImageProvider(user.photoUrl),
                  ),
                  Expanded(
                    flex: 1,
                    child: Column(
                      children: <Widget>[
                        Row(
                          mainAxisSize: MainAxisSize.max,
                          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                          children: <Widget>[
                            buildCountColumn("Videos", postCount),
                            buildCountColumn("Followers", 0),
                            buildCountColumn("Following", 0),
                          ],
                        ),
                        Row(
                          mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                          children: <Widget>[buildProfileButton()],
                        ),
                      ],
                    ),
                  ),
                ],
              ),
              Container(
                alignment: Alignment.centerLeft,
                padding: EdgeInsets.only(top: 12.0),
                child: Text(
                  user.username,
                  style: TextStyle(
                    fontWeight: FontWeight.bold,
                    fontSize: 16.0,
                  ),
                ),
              ),
              Container(
                alignment: Alignment.centerLeft,
                padding: EdgeInsets.only(top: 4.0),
                child: Text(
                  user.displayName,
                  style: TextStyle(
                    fontWeight: FontWeight.bold,
                  ),
                ),
              ),
              Container(
                alignment: Alignment.centerLeft,
                padding: EdgeInsets.only(top: 2.0),
                child: Text(
                  user.bio,
                ),
              ),
            ],
          ),
        );
      },
    );
  }

调试控制台显示：方法'[]'在null上被调用。接收者：null 尝试致电：相关的引起错误的小部件是 FutureBuilder

尽管如此，buildProfileButton（）也位于buildProfileHeader（）上方：

buildProfileButton() {
    bool isProfileOwner = currentUserId == widget.profileId;
    if (isProfileOwner) {
      return buildButton(text: "Edit Profile", function: editProfile);
    }
  }

Answer 1

在buildProfileButton（）函数中可以看到，如果条件为false，它将不返回任何内容。因此，您必须退货。

最后返回空容器可能是最好的解决方法。

方法'[]'在null和接收方上被调用：null-Flutter Android

1 个答案: