xylophone | Excel reports

As user @Saddan says, the TextButton class includes box constraints, meaning it will still have a size even without a child.

The real reason why you need a child widget is a bit more boring: There are very few reasons why you would want to have a TextWidget without a child, and even if you did, as I mention later in my answer, a more common approach to this is to use Container, which can be understood as an empty widget, because of this, the child property is considered required on the text widget (with null-safety, you get a compile-time error and without it, you get a lint warning like in the question).

The reason why child: null is added automatically is that flutter doesn't know what you want as your TextButton's child, but I believe you are meant to replace null with whatever else.

A TextButton should always have a child because if it doesn't it will not display anything, a text button can't size itself so it will always have the same size as its child, you need to put something on the child property or the text button will not know what to look like.

Now, you are passing null as the child, I will have to admit, I didn't think that was possible, I also don't think flutter likes this idea very much (If you activate null-safety, this code will throw a compile-time error). I think you should instead use Container, which is an empty-by-default widget as the child property:

this is happening because youur passing parameters can be null, so give them property required as below.

The link I provided in the comment above provides the answer you need. You just didn't implement it correctly. To specify a default for a selectInput with multiple=TRUE, you need to provide a vector of default values, not a scalar.

Here is a MWE to demonstrate.

You could do this by adjusting your plot function to have its formatting change with the number of categories it needs to show. Here, I make the size of the axis text adjust to the number of categories.

The code works perfectly for me. However, you can check the alignment of the image, maybe if you place it a bit more to the right you can see the label. For this try in the last chunk to add {r, fig.dim = c(5, 2.5), fig.align = 'right'}

After doing a bit of research, I came across an answer on Github. So to fix this issue you need to change ext.kotlin_version in build.gradle. To change that you need to right click on android folder from your project tree > click on Flutter > click on Open Android module in Android Studio > now you can open it in the same window or in a new one > click on Gradle Scripts from project tree> open build.gradle (the first file) > finally change the ext.kotlin_version parameter to the latest version in my case 1.5.30 and sync gradle project and you will be good to go.

You might be better off using the tr function, depending on your usage requirements:

You can try like this

Pass color as parameter and use MaterialStateProperty.all(color) to specify the color.