ListTile onLongPress Event Not working Flutter-CodePudding

I encountered weird issue while creating a learning Todo App. I implemented TaskList Class and TaskTile class as below.

TaskList Class as below

import 'package:provider/provider.dart';
import 'package:todoey/Models/taskdata.dart';
import 'package:todoey/widgets/task_tile.dart';

class TasksList extends StatefulWidget {
  @override
  State<TasksList> createState() => _TasksListState();
}

class _TasksListState extends State<TasksList> {
  @override
  Widget build(BuildContext context) {
    return Consumer<TaskData>(builder: (context, taskData, child) {
      return ListView.builder(
        itemBuilder: (context, index) {
          final task = taskData.taskList[index];
          return TaskTile(
            longPressCallBack: () {
              taskData.deleteTask(task);
            },
            name: task.name,
            isChecked: task.isDone,
            checkBoxCallBack: (newValue) {
              taskData.updateTask(task);
            },
          );
        },
        itemCount: taskData.taskList.length,
      );
    });
  }
}

TaskTile Class as below


class TaskTile extends StatelessWidget {
  final bool? isChecked;
  final String name;
  final Function checkBoxCallBack;
  final Function longPressCallBack;

  TaskTile(
      {required this.name,
      this.isChecked,
      required this.checkBoxCallBack,
      required this.longPressCallBack});

  @override
  Widget build(BuildContext context) {
    return ListTile(
      title: Text(
        name,
        style: TextStyle(
          decoration: isChecked! ? TextDecoration.lineThrough : null,
        ),
      ),
      trailing: Checkbox(
        fillColor: MaterialStateProperty.all(Colors.lightBlueAccent),
        checkColor: Colors.white,
        value: isChecked!,
        onChanged: (newValue) {
          checkBoxCallBack(newValue);
        },
      ),
      onLongPress: () => longPressCallBack,
    );
  }
}

Now the problem is it doesn't call longPressCallBack of parent class i.e. TaskList class. I debugged and it calls onLongPress of TaskTile class but not calling callback to it's parent class and that is why deleteTask not working.

CodePudding user response：

The problem is with this line onLongPress: () => longPressCallBack, on your TaskTile class. Here you are just invoking longPressCallBack closure reference instead of executing the closure function.

Solution:

Change that line to this : onLongPress: () => longPressCallBack(), or try directly passing function refrence to onLongPress property of ListTile like this onLongPress: longPressCallBack,

CodePudding user response：

You can use VoidCallback instead, look at the following sample code:

class _MyWidgetState extends State<MyWidget> {
  String greeting = "Hello World!";
  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        Text(
          greeting,
          style: Theme.of(context).textTheme.headline4,
        ),
        TestButton(
          onClickCallback: () {
            setState(() {
              greeting = "Hello Test!";
            });
            
          }
        ),
      ],
    );
  }
}

class TestButton extends StatelessWidget {
  final VoidCallback onClickCallback;
  
  const TestButton( {required this.onClickCallback});
  
  @override
  Widget build(BuildContext context) {
    return ElevatedButton(
      child: const Text("TestButton"),
      onPressed: onClickCallback,
    );
      
  }
}