Saving a list of widgets throws findRenderObject was called on null exception.

[tehsunnliu]

I have a list of items in
ListView(), not ListView.builder(). And in the ListView each child is wrapped with Screenshot widget.
When the ListView is built I store the Screenshot controller for each widget in a list.
When trying to capture only the first widget gets captured and then I get this exception

/flutter ( 2557): Caught error: NoSuchMethodError: The method 'findRenderObject' was called on null.
I/flutter ( 2557): Receiver: null
I/flutter ( 2557): Tried calling: findRenderObject()
I/flutter ( 2557): #0      ScreenshotController.capture.<anonymous closure>
package:screenshot/screenshot.dart:41
I/flutter ( 2557): #1      new Future.delayed.<anonymous closure> (dart:async/future.dart:326:39)
I/flutter ( 2557): #2      _rootRun (dart:async/zone.dart:1182:47)
I/flutter ( 2557): #3      _CustomZone.run (dart:async/zone.dart:1093:19)
I/flutter ( 2557): #4      _CustomZone.runGuarded (dart:async/zone.dart:997:7)
I/flutter ( 2557): #5      _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1037:23)
I/flutter ( 2557): #6      _rootRun (dart:async/zone.dart:1190:13)
I/flutter ( 2557): #7      _CustomZone.run (dart:async/zone.dart:1093:19)
I/flutter ( 2557): #8      _CustomZone.bindCallback.<anonymous closure> (dart:async/zone.dart:1021:23)
I/flutter ( 2557): #9      Timer._createTimer.<anonymous closure> (dart:async-patch/timer_patch.dart:18:15)
I/flutter ( 2557): #10     _Timer._runTimers (dart:isolate-patch/timer_impl.dart:397:19)
I/flutter ( 2557): #11     _Timer._handleMessage (dart:isolate-patch/timer_impl.dart:428:5)
I/flutter ( 2557): #12     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:168:12)

[callmejm]

same +1

[yogi0823]

Screenshot(
controller: screenshotController,
child: Component(),
),

wrapp your widget with Screenshot()

[ritheshSalyan]

@tehsunnliu how exactly do you need? do you want to take a screenshot of the entire list at once like this? or
screenshot of individual elements on some event like this?

[tehsunnliu]

Hi, I wanted to capture individual elements in the listview, I wrapped ewach element in the listview with Screenshot widget but it doesn't work. I get same error as mentioned earlier.
Since in my case the listview won't contain many elements I chose not to use listview and created a column with the elements. This way I was able to take screenshots of each element individually.

[BhavyKoshti9spl]

created list view like this :

ListView.separated( shrinkWrap: false, itemBuilder: (context, position) => getPost(position), separatorBuilder: (context, position) { return Container( height: 4, color: Colors.transparent, ); }, scrollDirection: Axis.vertical, controller: _scrollController, itemCount: feedList.length, )

and i wrapped each item with screenshot with different controller each time , actually i take one var in list and assigned controller to it if its null so this way every item has its different controller and while i am trying to capture it it gives me error like above

the same way i did this in different page and working file i couldn't find any difference in it ,

in my list there are too many items so i can't put columns there.

[BhavyKoshti9spl]

any updates ? @SachinGanesh

[stevendz]

Had the same problem, I guess the easiest way is replacing the ListView with a SingleChildScrollView and a Column, you will lose the lazy loading but the screenshots will work.