sliding_up_panel

A draggable Flutter widget that makes implementing a SlidingUpPanel much easier! Based on the Material Design bottom sheet component, this widget works on both Android & iOS.

Installing

Add the following to your pubspec.yaml file:

dependencies:
  sliding_up_panel: ^0.3.4

Simple Usage

There are two ways which the SlidingUpPanel can easily be added to your project.

1. Using the SlidingUpPanel as the root widget for the body (recommended).
2. Nesting the SlidingUpPanel

SlidingUpPanel as the Root (recommended)

This method is recommended as it allows for the least interference with the behavior of other UI elements. For example:

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text("SlidingUpPanelExample"),
    ),
    body: SlidingUpPanel(
      panel: Center(
        child: Text("This is the sliding Widget"),
      ),
      body: Center(
        child: Text("This is the Widget behind the sliding panel"),
      ),
    ),
  );
}

Nesting the SlidingUpPanel

This method isn't recommended but can still be used. Only use this to avoid refactoring large chunks of code or to implement custom scrolling behavior. For example, the SlidingUpPanel can be nested inside of a Stack (note that there are many other possible implementations that vary on a case-by-case basis).

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text("SlidingUpPanelExample"),
    ),
    body: Stack(
      children: <Widget>[
        Center(child: Text("This is the Widget behind the sliding panel"),),

        SlidingUpPanel(
          panel: Center(child: Text("This is the sliding Widget"),),
        )
      ],
    )
  );
}

Screenshots

Both methods produce the same result:

Custom Usage

There are several options that allow for more control:

Properties	Description
panel	(required) The Widget that slides into view. When the panel is collapsed and if collapsed is null, then top portion of this Widget will be displayed; otherwise, collapsed will be displayed overtop of this Widget.
collapsed	The Widget displayed overtop the panel when collapsed. This fades out as the panel is opened.
body	The Widget that lies underneath the sliding panel. This Widget automatically sizes itself to fill the screen.
minHeight	The height of the sliding panel when fully collapsed.
maxHeight	The height of the sliding panel when fully open.
border	A border to draw around the sliding panel sheet.
borderRadius	If non-null, the corners of the sliding panel sheet are rounded by this.
boxShadow	A list of shadows cast behind the sliding panel sheet.
color	The color to fill the background of the sliding panel sheet.
padding	The amount to inset the children of the sliding panel sheet.
margin	Empty space surrounding the sliding panel sheet.
renderPanelSheet	Set to false to not to render the sheet the panel sits upon. This means that only body, collapsed, and the panel Widgets will be rendered. Set this to false if you want to achieve a floating effect or want more customization over how the sliding panel looks like.
panelSnapping	Set to false to disable the panel from snapping open or closed.
backdropEnabled	If non-null, shows a darkening shadow over the body as the panel slides open.
backdropColor	Shows a darkening shadow of this Color over the body as the panel slides open.
backdropOpacity	The opacity of the backdrop when the panel is fully open. This value can range from 0.0 to 1.0 where 0.0 is completely transparent and 1.0 is completely opaque.
backdropTapClosesPanel	Flag that indicates whether or not tapping the backdrop closes the panel. Defaults to true.
controller	If non-null, this can be used to control the state of the panel.
onPanelSlide	If non-null, this callback is called as the panel slides around with the current position of the panel. The position is a double between 0.0 and 1.0 where 0.0 is fully collapsed and 1.0 is fully open.
onPanelOpened	If non-null, this callback is called when the panel is fully opened.
onPanelClosed	If non-null, this callback is called when the panel is fully collapsed.
parallaxEnabled	If non-null and true, the SlidingUpPanel exhibits a parallax effect as the panel slides up. Essentially, the body slides up as the panel slides up.
parallaxOffset	Allows for specifying the extent of the parallax effect in terms of the percentage the panel has slid up/down. Recommended values are within 0.0 and 1.0 where 0.0 is no parallax and 1.0 mimics a one-to-one scrolling effect. Defaults to a 10% parallax.
isDraggable	Allows toggling of draggability of the SlidingUpPanel. Set this to false to prevent the user from being able to drag the panel up and down. Defaults to true.
slideDirection	Either SlideDirection.UP or SlideDirection.DOWN. Indicates which way the panel should slide. Defaults to UP. If set to DOWN, the panel attaches itself to the top of the screen and is fully opened when the user swipes down on the panel.

Darkening the Body as the Panel Opens

If desired, the body can be darkened as the panel is opened by setting backdropEnabled to true. You can also customize the backdropColor, backdropOpacity, and backdropTapClosesPanel. For example:

@override
Widget build(BuildContext context){
  return Material(
    child: SlidingUpPanel(
      backdropEnabled: true,
      panel: Center(
        child: Text("This is the sliding Widget"),
      ),
      body: Scaffold(
        appBar: AppBar(
          title: Text("SlidingUpPanelExample"),
        ),
        body:  Center(
          child: Text("This is the Widget behind the sliding panel"),
        ),
      ),
    ),
  );
}

Notice how the Scaffold is nested inside of the SlidingUpPanel. This because the backdrop is rendered only over the body of the SlidingUpPanel. As a result, if we want the backdrop to appear over the AppBar, then we must nest the Scaffold this way.

Displaying a Different Child When the Panel is Closed

By assigning a non-null Widget to the collapsed property, you can add a Widget that displays overtop the panel when collapsed. As the panel is opened, this Widget will fade out to display the panel underneath. For example:

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text("SlidingUpPanelExample"),
    ),
    body: SlidingUpPanel(
      panel: Center(
        child: Text("This is the sliding Widget"),
      ),
      collapsed: Container(
        color: Colors.blueGrey,
        child: Center(
          child: Text(
            "This is the collapsed Widget",
            style: TextStyle(color: Colors.white),
          ),
        ),
      ),
      body: Center(
        child: Text("This is the Widget behind the sliding panel"),
      ),
    ),
  );
}

Rounding the Borders

Modern design principles (especially in the Material Design Refresh) emphasize rounded borders. A similar effect can be easily achieved by providing a non-null BorderRadiusGeometry to the borderRadius property. Note that this only curves the border on the underlying panel sheet: any children passed to panel or collapsed must also have their borders curved separately in order to achieve a uniform effect. For example:

@override
Widget build(BuildContext context) {
  BorderRadiusGeometry radius = BorderRadius.only(
    topLeft: Radius.circular(24.0),
    topRight: Radius.circular(24.0),
  );

  return Scaffold(
    appBar: AppBar(
      title: Text("SlidingUpPanelExample"),
    ),
    body: SlidingUpPanel(
      panel: Center(
        child: Text("This is the sliding Widget"),
      ),

      collapsed: Container(
        decoration: BoxDecoration(
          color: Colors.blueGrey,
          borderRadius: radius
        ),
        child: Center(
          child: Text(
            "This is the collapsed Widget",
            style: TextStyle(color: Colors.white),
          ),
        ),
      ),

      body: Center(
        child: Text("This is the Widget behind the sliding panel"),
      ),

      borderRadius: radius,
    ),
  );
}

Creating A Floating Effect

To create a fully custom effect, the default panel sheet can be completely hidden and only the children rendered (i.e. only body, panel, and collapsed are rendered). To do this, set the renderPanelSheet property to false. For example, to create a floating effect:

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text("SlidingUpPanelExample"),
    ),
    body: SlidingUpPanel(
      renderPanelSheet: false,
      panel: _floatingPanel(),
      collapsed: _floatingCollapsed(),
      body: Center(
        child: Text("This is the Widget behind the sliding panel"),
      ),
    ),
  );
}

Widget _floatingCollapsed(){
  return Container(
    decoration: BoxDecoration(
      color: Colors.blueGrey,
      borderRadius: BorderRadius.only(topLeft: Radius.circular(24.0), topRight: Radius.circular(24.0)),
    ),
    margin: const EdgeInsets.fromLTRB(24.0, 24.0, 24.0, 0.0),
    child: Center(
      child: Text(
        "This is the collapsed Widget",
        style: TextStyle(color: Colors.white),
      ),
    ),
  );
}

Widget _floatingPanel(){
  return Container(
    decoration: BoxDecoration(
      color: Colors.white,
      borderRadius: BorderRadius.all(Radius.circular(24.0)),
      boxShadow: [
        BoxShadow(
          blurRadius: 20.0,
          color: Colors.grey,
        ),
      ]
    ),
    margin: const EdgeInsets.all(24.0),
    child: Center(
      child: Text("This is the SlidingUpPanel when open"),
    ),
  );
}

Note that a similar effect can be created by simply adding a margin to the SlidingUpPanel.

Adding Scrollable Elements to the Sliding Panel

The panel itself can contain Scrollable elements. However, it's important to note that when other Scrollable Widgets are nested inside of the panel, you need to incorporate some empty space (i.e. non-scrolling space) at the top which the user can swipe down on to close the panel. For example:

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text("SlidingUpPanelExample"),
    ),
    body: SlidingUpPanel(
      color: Colors.blueGrey,
      panel: _scrollingList(),
      body: Center(
        child: Text("This is the Widget behind the sliding panel"),
      ),
    ),
  );
}

Widget _scrollingList(){
  return Container(
    //adding a margin to the top leaves an area where the user can swipe
    //to open/close the sliding panel
    margin: const EdgeInsets.only(top: 36.0),

    color: Colors.white,
    child: ListView.builder(
      itemCount: 50,
      itemBuilder: (BuildContext context, int i){
        return Container(
          padding: const EdgeInsets.all(12.0),
          child: Text("$i"),
        );
      },
    ),
  );
}

Using the PanelController

At times, it can be useful to manually change the state of the SlidingUpPanel. This can be easily achieved by using a PanelController and attaching it to an instance of the SlidingUpPanel. Note that since the PanelController modifies the state of a SlidingUpPanel, these methods can only be called after the SlidingUpPanel has been rendered.

Methods	Description
open()	Opens the sliding panel fully (i.e. to the maxHeight)
close()	Closes the sliding panel to its collapsed state (i.e. to the minHeight)
hide()	Hides the sliding panel (i.e. is invisible)
show()	Shows the sliding panel in its collapsed state (i.e. "un-hide" the sliding panel)
setPanelPosition(double value)	Sets the panel position (without animation). The value must between 0.0 and 1.0 where 0.0 is fully collapsed and 1.0 is completely open.
animatePanelToPosition(double value)	Animates the panel position to the value. The value must between 0.0 and 1.0 where 0.0 is fully collapsed and 1.0 is completely open.
getPanelPosition()	Gets the current panel position. Returns the % offset from collapsed state to the open state as a decimal between 0.0 and 1.0 where 0.0 is fully collapsed and 1.0 is full open.
isPanelAnimating()	Returns whether or not the panel is currently animating.
isPanelOpen()	Returns whether or not the panel is open.
isPanelClosed()	Returns whether or not the panel is collapsed.
isPanelShown()	Returns whether or not the panel is shown/hidden.

PanelController _pc = new PanelController();

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: Text("SlidingUpPanelExample"),
    ),
    body: SlidingUpPanel(
      controller: _pc,
      panel: Center(
        child: Text("This is the sliding Widget"),
      ),
      body: _body(),
    ),
  );
}

Widget _body(){
  return Container(
    child: Column(
      children: <Widget>[
        RaisedButton(
          child: Text("Open"),
          onPressed: () => _pc.open(),
        ),
        RaisedButton(
          child: Text("Close"),
          onPressed: () => _pc.close(),
        ),
        RaisedButton(
          child: Text("Show"),
          onPressed: () => _pc.show(),
        ),
        RaisedButton(
          child: Text("Hide"),
          onPressed: () => _pc.hide(),
        ),
      ],
    ),
  );
}