多選項目

multi_select_item

Multi select view item controller for GridView and ListView in Flutter

Getting Started

For this to work. You need to write First define the controller first

MultiSelectController controller = new MultiSelectController();

Then set the controller length from your list length

//your list here, can be what ever you want.
mainList.add({"key": "1"});
mainList.add({"key": "2"});
mainList.add({"key": "3"});
mainList.add({"key": "4"});

controller.set(mainList.length);

Finally you can use it with list builder. For this plugin to work, you need to provide the MultiSelectItem widget with isSelecting parameter and onSelected parameter.

• the isSelecting parameter will be used to tell the widget from the controller wether it's in multi selecting mode or not.
• the onSelected parameter is a function. The function will be called depending wether it's in multi selecting mode (isSelecting == true) or not.
  • if isSelecting is true, then the function will be called when user tap on the MultiSelectItem widget
  • if isSelecting is false, then the function will be called when user longtap on the MultiSelectItem widget

So in basic, it will look like this:

ListView.builder(
  itemCount: mainList.length,
  itemBuilder: (context, index) {
    return MultiSelectItem(
      isSelecting: controller.isSelecting,
      
      //the function that will be called when item is long-tapped/tapped
      onSelected: () {
        setState(() {
          controller.toggle(index);
        });
      },
      child: Container(
        child: ListTile(
          title: new Text("Title ${mainList[index]['key']}"),
          subtitle: new Text("Description ${mainList[index]['key']}"),
        ),
        
        //change color based on wether the id is selected or not.
        decoration: controller.isSelected(index)
            ? new BoxDecoration(color: Colors.grey[300])
            : new BoxDecoration(),
      ),
    );
  },
),

Now you can multi select and get the selected indexes:

print(controller.selectedIndexes.toString());

Changing List

If you ever change the list wether adding or removing item in it, don't forget to call set() with setState() and pass in your list's length to update the controller.

mainList.add({"key": mainList.length + 1});

setState(() {
  controller.set(mainList.length);
});

Removing Item from List

Removing item can be tricky. When we select items, it will store the index in selectedIndexes list, but it will order by last selected. As such, it will cause error if we just loop through the list and delete one by one. To avoid this, reorder the list from biggest id to smallest id first and then delete one by one.

var list = controller.selectedIndexes;
list.sort((b, a) =>
    a.compareTo(b)); //reoder from biggest number, so it wont error
list.forEach((element) {
  mainList.removeAt(element);
});

setState(() {
  controller.set(mainList.length);
});

Keep in Selecting Mode

Sometimes, you don't want to quit multi selecting mode even no item is selected. To do this, add and set disableEditingWhenNoneSelected to false.

controller.disableEditingWhenNoneSelected = false;
controller.set(mainList.length);

Enter Selecting Mode Manually

You can enter selecting mode by changing parameter isSelecting of the controller to true.
Don't forget to use setState()!

setState(() {
  controller.isSelecting = true;
});

MultiSelectItem Parameters

MultiSelectItem is a widget that handles the multi selecting. Wrap this widget inside listbuilder item.

//child widget to pass
final Widget child;

//variable to tell the MultiSelectItem wether it's in selecting mode or not.
final bool isSelecting;

//function that will be called based on isSelecting variable.
//if isSelecting is true, then the function will be called when user tap on the MultiSelectItem widget
//if isSelecting is false, then the function will be called when user long tap on the MultiSelectItem widget
final VoidCallback onSelected;

MultiSelectController Parameters

MultiSelectController is a controller that hadles the state of the multi selecting.

//list of selected indexes
List<int> selectedIndexes;

//the state wether it's in multi selecting mode or not
bool isSelecting = false;

//if set to false, it will not get out from multi selecting mode if no item are selected
bool disableEditingWhenNoneSelected = true;

MultiSelectController Functions

Function	Return Type	Parameter	Description
set	void		set the controller length
isSelected	bool	int i	returns if the specified id is being selected or not
select	void	int i	select specified id
deselect	void	int i	deselect specified id
toggle	void	int i	toggle specified id
selectAll	void		select all
deselectAll	void		deselect all
toggleAll	void		select all if not all list item is selected. deselect all if all list item is selected.