setstate

问题 I've been looking around and it seems the most efficient and resource friendly way of animating a CustomPainter is to pass it an AnimationController as a repaint listenable, rather than using SetState(). I've tried this method, but unfortunately my CustomPaint object requires a variable that can be set both by the controller.value but also by the position of a user's pointer during a drag. class CustomScroller extends StatefulWidget { final double width; //Should be width of user's screen

问题 I've been looking around and it seems the most efficient and resource friendly way of animating a CustomPainter is to pass it an AnimationController as a repaint listenable, rather than using SetState(). I've tried this method, but unfortunately my CustomPaint object requires a variable that can be set both by the controller.value but also by the position of a user's pointer during a drag. class CustomScroller extends StatefulWidget { final double width; //Should be width of user's screen

问题 I've been looking around and it seems the most efficient and resource friendly way of animating a CustomPainter is to pass it an AnimationController as a repaint listenable, rather than using SetState(). I've tried this method, but unfortunately my CustomPaint object requires a variable that can be set both by the controller.value but also by the position of a user's pointer during a drag. class CustomScroller extends StatefulWidget { final double width; //Should be width of user's screen

问题 Why is using componentDidUpdate more recommended over the setState callback function (optional second argument) in React components (if synchronous setState behavior is desired)? Since setState is asynchronous, I was thinking about using the setState callback function (2nd argument) to ensure that code is executed after state has been updated, similar to then() for promises. Especially if I need a re-render in between subsequent setState calls. However, the official React Docs say "The second

问题 Why is using componentDidUpdate more recommended over the setState callback function (optional second argument) in React components (if synchronous setState behavior is desired)? Since setState is asynchronous, I was thinking about using the setState callback function (2nd argument) to ensure that code is executed after state has been updated, similar to then() for promises. Especially if I need a re-render in between subsequent setState calls. However, the official React Docs say "The second

问题 I'm currently dealing with a problem where I need some data from an API to show it into my widgets. I've following some Provider architecture pattern, where you setState two times: 1- When data is being fetched 2- When data is already fetched So the problem I'm currently dealing is, my widget throws the following error: setState() or markNeedsBuild() called during build. I know this error is because setState is called during build, but.. how can I fetch my api during build, and then show it

问题 I need a bit of help. I am new to react, so I have stuck here. I have shared a sandbox box link. That Contains a Table. as below | Toy | Color Available | Cost Available | Now everything works perfectly. But I want to save the data of the table as below The detail state should contain a list of row values of the table and the columnsValues should contain the checkbox value of Color Available and Cost Available Example: this.state.detail like detail: [ { toy : ... color : ... cost : ... } {

问题 I have a streambuilder that loads information from firestore. Then I use a listview.builder to display the information. The displayed information is being called by the function firstBuildItem or buildItem. The functionality that I want is that when the user clicks on the container that is wrapped with a gesturedetector, I want another widget to be expanded below the main widget. I'm not sure how to achieve this with flutter because since each message is an item insider listview.builder, the

问题 I'm designing a form in React that has a main form builder (Create Job.js) and some form pages (AdditionalInfo.js) and (Confirmation.js) . this form had a tag input that allows you to choose tags from a drop-down list provided by an API. the selected items need to be shown later in the confirmation page. This is my main form builder that has props and functions: (CreateJob.js) state = { step:1, Title:'', requirements:'', Location:'', Benefits:'', Company:'', InternalCode:'', Details:'', Tags:

问题 I am using the method in this question to change the body of a Scaffold in flutter: Flutter Drawer Widget - change Scaffold.body content The method described works perfectly. Now I would like just the drawer to automatically close after the users taps on one of the items. I tried using the Navigator.pop() method, but it pops the entire screen, not just the drawer. It leaves me with a totally black screen. Any suggestions? 回答1: Are you using exactly Navigator.of(context).pop() ? I cannot