根据Dart Code Metrics，这是对Dart代码设计的警告，避免在预期同步的情况下调用异步函数。
avoid-passing-async-when-sync-expected
为了避免抱怨，现在有两种方法。
1.使用then（）方法

OutlinedButton.icon(
    icon: Icon(Icons.upload),
    label: Text("Select profile picture"),
    onPressed: () {
        introVM.imagePicker.pickImage(
            source: ImageSource.gallery, 
            imageQuality: 50,
            preferredCameraDevice: CameraDevice.front
        ).then((XFile? xFile) {
             if (xFile != null) introVM.setProfilePicture(xFile!.path);
        });
    },
);

1.使用匿名函数（我不喜欢这个函数，我们应该把它转换成一个单独的函数）

OutlinedButton.icon(
    icon: Icon(Icons.upload),
    label: Text("Select profile picture"),
    onPressed: () {
        // Should move to a separate function
        () async {
            XFile? image = await introVM.imagePicker.pickImage(
                source: ImageSource.gallery,
                imageQuality: 50,
                preferredCameraDevice: CameraDevice.front);
            if (image != null) introVM.setProfilePicture(image!.path);
         };
    },
);