In this guide we will learn how to implement button functionality using material button widgets.

• Basic Widgets or Classes to implement button functionality
  • FlatButton Class
  • RaisedButton Class
  • IconButton Class
  • FloatingActionButton Class
• Advanced Widgets or Classes to implement button functionality
  • ButtonBar
  • DropdownButton
  • PopupMenuButton

In this guide, we will cover all the material button widgets listed on the official flutter docs - Material Button Documentation

Flutter Material Button Documentation

Let us start with the simplest way to implement buttons in flutter

1. FlatButton Class - Documentation

Also refer official class documentation with this guide to deeply understand the concept.

A flat button is a text label displayed on a zero elevation Material widget.

FlatButton Class Constructor

FlatButton({Key key, @required VoidCallback onPressed, ValueChanged<bool> onHighlightChanged, ButtonTextTheme textTheme, Color textColor, Color disabledTextColor, Color color, Color disabledColor, Color focusColor, Color hoverColor, Color highlightColor, Color splashColor, Brightness colorBrightness, EdgeInsetsGeometry padding, ShapeBorder shape, Clip clipBehavior, FocusNode focusNode, bool autofocus: false, MaterialTapTargetSize materialTapTargetSize, @required Widget child })

Required Parameters 

• ‘onPressed’ parameter is required
• ‘child’ parameter is required

FlatButton Implementation

lets add some more parameters or properties : refer official class documentation for property list 

FlatButton Color Parameters

How to disable a button ?

Set onPressed VoidCallback to ‘null’

FlatButton Disabled

FlatButton.icon Constructor

FlatButton.icon Constructor

2. RaisedButton Class - Documentation

Also refer official class documentation with this guide to deeply understand the concept.

Button with elevation

RaisedButton Class Constructor

RaisedButton({Key key, @required VoidCallback onPressed, ValueChanged<bool> onHighlightChanged, ButtonTextTheme textTheme, Color textColor, Color disabledTextColor, Color color, Color disabledColor, Color focusColor, Color hoverColor, Color highlightColor, Color splashColor, Brightness colorBrightness, double elevation, double focusElevation, double hoverElevation, double highlightElevation, double disabledElevation, EdgeInsetsGeometry padding, ShapeBorder shape, Clip clipBehavior, FocusNode focusNode, bool autofocus: false, MaterialTapTargetSize materialTapTargetSize, Duration animationDuration, Widget child })

Required Parameters

• ‘onPressed’ parameter is required

RaisedButton Implementation

lets add some more parameters or properties : refer official class documentation for property list 

RaisedButton Color Parameters

RaisedButton.icon Constructor

RaisedButton.icon Constructor

3. IconButton Class - Documentation

Also refer official class documentation with this guide to deeply understand the concept.

IconButton Class Constructor

IconButton({Key key, double iconSize: 24.0, EdgeInsetsGeometry padding: const EdgeInsets.all(8.0), AlignmentGeometry alignment: Alignment.center, @required Widget icon, Color color, Color focusColor, Color hoverColor, Color highlightColor, Color splashColor, Color disabledColor, @required VoidCallback onPressed, FocusNode focusNode, bool autofocus: false, String tooltip })

Required Parameters

• ‘onPressed’ parameter is required
• ‘icon’ parameter is required

IconButton Class Implementation

lets add some more parameters or properties : refer official class documentation for property list 

IconButton Color Parameters

4. FloatingActionButton Class - Documentation

Also refer official class documentation with this guide to deeply understand the concept.

• floating action button is a circular icon button that hovers over content to promote a primary action.
• Use at most single floating action button per screen

FloatingActionButton Class Constructor

FloatingActionButton({Key key, Widget child, String tooltip, Color foregroundColor, Color backgroundColor, Color focusColor, Color hoverColor, Color splashColor, Object heroTag: const \_DefaultHeroTag(), double elevation, double focusElevation, double hoverElevation, double highlightElevation, double disabledElevation, @required VoidCallback onPressed, bool mini: false, ShapeBorder shape, Clip clipBehavior: Clip.none, FocusNode focusNode, bool autofocus: false, MaterialTapTargetSize materialTapTargetSize, bool isExtended: false })

Required Parameters

• ‘onPressed’ parameter is required

Scaffold has a floatingActionButton Parameter - Scaffold Constructor Documentation

FloatingActionButton Implementation

lets add some more parameters or properties : refer official class documentation for property list 

FloatingActionButton Tooltip

FloatingActionButton.extended constructor

FloatingActionButton.extended({Key key, String tooltip, Color foregroundColor, Color backgroundColor, Color focusColor, Color hoverColor, Object heroTag: const \_DefaultHeroTag(), double elevation, double focusElevation, double hoverElevation, Color splashColor, double highlightElevation, double disabledElevation, @required VoidCallback onPressed, ShapeBorder shape, bool isExtended: true, MaterialTapTargetSize materialTapTargetSize, Clip clipBehavior: Clip.none, FocusNode focusNode, bool autofocus: false, Widget icon, @required Widget label })

Required Parameters

• ‘onPressed’ parameter is required
• ‘label’ parameter is required

FloatingActionButton.extended Constructor

5. ButtonBar Class - Documentation

Also refer official class documentation with this guide to deeply understand the concept.

• Use this class when you have to display multiple buttons in a horizontal layout.
• Do not use row widget, instead use ButtonBar class which is designed to acheive such common layouts effectively.

ButtonBar Class Constructor

ButtonBar({Key key, MainAxisAlignment alignment: MainAxisAlignment.end, MainAxisSize mainAxisSize: MainAxisSize.max, List<Widget> children: const [] })

children [] - List of the buttons to be arranged horizontally. 

lets add some more parameters or properties : refer official class documentation for property list 

• alignment: MainAxisAlignment.center - How the children should be placed along the horizontal axis.
• mainAxisSize: MainAxisSize.max - How much horizontal space is available.

ButtonBar Implementation

6. DropdownButton Class - Documentation

Also refer official class documentation with this guide to deeply understand the concept.

A dropdown button lets the user select from a number of items. Dropdown button allows us build simple input user interface to select list items. Common examples - select countries, currencies, states etc in our flutter app

DropdownButton Class Constructor

DropdownButton({Key key, @required List<DropdownMenuItem<T>> items, T value, Widget hint, Widget disabledHint, @required ValueChanged<T> onChanged, int elevation: 8, TextStyle style, Widget underline, Widget icon, Color iconDisabledColor, Color iconEnabledColor, double iconSize: 24.0, bool isDense: false, bool isExpanded: false })

Required Parameters

• items

Implementation

• Create a Dropdown StatefulWidget
• Create a list of dropdown items
• Create a variable for default selected item

• 3 main properties required for DropdownButton class implementation

  • items
  • onChanged
  • value
• items property will contain DropdownMenuItem class implementation as shown below

• 2 main properties required to implement DropdownMenuItem class

  • value
  • child - Text Widget

DropdownButton Class Implementation

lets add some more parameters or properties : refer official class documentation for property list 

icon - The widget to use for the drop-down button’s icon

• iconEnabledColor
• iconDisabledColor

DropdownButton Class Properties

7. PopupMenuButton<T> class - Documentation

Also refer official class documentation with this guide to deeply understand the concept.

When this button is pressed, it displays a menu (pop-up menu).

PopupMenuButton Class Constructor

PopupMenuButton({Key key, @required PopupMenuItemBuilder<T> itemBuilder, T initialValue, PopupMenuItemSelected<T> onSelected, PopupMenuCanceled onCanceled, String tooltip, double elevation, EdgeInsetsGeometry padding: const EdgeInsets.all(8.0), Widget child, Icon icon, Offset offset: Offset.zero, bool enabled: true, ShapeBorder shape, Color color })

Required Parameters 

• itemBuilder

Implementation

• Create a list of popup menu items

• 3 main properties required for PopupMenuButton class implementation

  • itemBuilder 
  • onSelected
• itemBuilder property will contain PopupMenuItem class implementation as shown below

• 2 main properties required to implement PopupMenuItem class

  • value
  • child - Text Widget

PopupMenuButton Class Implementation

lets add some more parameters or properties : refer official class documentation for property list 

• icon property to change popup menu button
• tooltip - text that describe the action that will occur when the button is pressed
• onCanceled - the function defined here will be called when user dismisses popup menu without selecting any option

PopupMenuButton Class Properties

PopupMenuButton sample implementation - add settings popup menu button

Settings PopupMenuButton

Coding - Sample Flutter App Code

Bonus Tip : Also refer the following classes to improve your PopupMenu UI

• PopupMenuDivider - a popup menu entry that is just a horizontal line - Documentation
• CheckedPopupMenuItem - a popup menu item with a checkmark - Documentation

To learn more about flutter - Flutter Developer Guide
There are two more classes using which we can implement button functionality

• GestureDetector Class
• InkWell Class

We will cover this in Flutter Gestures Guide.