Flutter Provider 重建不必要的小部件

Question

I am building a mobile app with provider architecture on flutter.

As per the design, I am using a model with changeNotifier which has a list of objects in it.

Whenever there is a change in one of the list object the whole list is getting rebuilt which not supposed to be.

To simulate this, I have created a simple app like below. The top line is a list of items, whereas the bottom one is the detailed widget. But whenever I tap both the list widget and the detailed widget is getting rebuilt.

Here is the source code. Github Link

Here is the sample screenshot

Here are my questions.

1. How to listen only to the child object?
2. What is the mistake I have made here?

Answer 1

The provider state management package offerers consumers. When using consumers you have the option to pass in in a child widget which you do don't wish to rebuild. And a builder methods which then accepts the child(which is mostly in this state static and doesn't need rebuilding) together with the widget which are to be rebuilt in your case the bottom detail card if I'm not mistaking. You can lesrn more from the docs provided they're very self explanatory. https://github.com/rrousselGit/provider/blob/master/README.md

Also the medium post in this link explains a lot on how the provider package works. https://medium.com/flutter-nyc/a-closer-look-at-the-provider-package-993922d3a5a5

Answer 2

老实说，我认为您不需要担心完全重建，但如果它困扰您，有一个 Selector 小部件，您可以使用它来收听列表中项目的特定值。

Answer 3

Maybe it is a bit late, But for anyone has this problem. Provider is just a dependency injection framework, You can not use it for state management (alone). You should've provided us with a sample of your code, but I will assume that You're using Provider with ChangeNotifier . In this situation You just have to use the Consumer Widget that have a build function inside this function You put your that is gonna be rebuilt.. Here is a Medium article

Another way is to use a combination of Provider and Streams and you can use StreamBuilder Widget the same way you use Consumer ..