xml_widget

xml_widget is a flutter library that could dynamically parse xml file into flutter widgets with javascript as execution engine. It is still in development.

similar to android's layout

Node name and attributes are exactly same with flutter widgets'.

<Center>
  <Column
    flutter:mainAxisAlignment="center">
    <Text
      flutter:data="Flutter Xml Widget"/>
    <Container
      flutter:margin="16dp"
      flutter:padding="16dp">
        <Text flutter:data="Text in a container"/>
    </Container>
  </Column>
</Center>

Very similar to Android's layout resources file if you did some android development! The attributes are just what corresponding widget have, with 'flutter:' as prefix. Equal dart code:

Center(
  child: Column(
    mainAxisAlignment: MainAxisAlignment.center,
    children: <Widget>[
      Text(
        'Flutter Xml Widget',
      ),
      Container(
        margin: EdgeInsets.all(16),
        padding: EdgeInsets.all(16),
        child: Text(
          'Text in a container',
        ),
      ),
    ],
  ),
)

Different from android's building xml as resource, xml_widget could directly read local xml file from device's storage. So you could download remote file from server and experience smooth GUI by flutter's high performance rendering!

object properties

simple property

some widget's property has a few sub-properties, such as Container's constraints, we treat it as simple property, just using . to directly declare attributes in xml:

<Container
  flutter:constraints.minWidth="120dp"
  flutter:constraints.minHeight="40dp">
</Container>

builtin resources

you could directly use some built-in color/theme/style already defined by flutter framework:

<Container
  flutter:color="@flutter:color/orangeAccent">
  <Text
    flutter:data="Flutter Xml Widget"
    flutter:style="@@flutter:theme/textTheme.headline4"/>
</Container>

Container would use Colors.orangeAccent as background and Text widget would apply Theme.of(context).theme.textTheme.headline4

property override

want a slight change to given resource?

<Text
  flutter:style="@flutter:theme/textTheme.headline4"
  flutter:style.color="@flutter:color/red"/>

it corresponds dart's copyWith:

Text(
  style: Theme.of(context).textTheme.headline4.copyWith(color: Colors.red),
);

custom color

if you hope to use your own color resource, just declare as follow in colors.xml placed in same directory with your layout xml:

<resources>
  <color name="orange">@flutter:color/orange</color>
  <color name="darkGreen">#1b8523</color>
  <color name="darkBlue">#1b5485</color>
</resources>

then using it without prefix:

<Container
  flutter:color="@color/orange">
  <Text
    flutter:data="Flutter Xml Widget"
    flutter:style="@flutter:theme/textTheme.headline4"
    flutter:style.color="@color/darkBlue"/>
</Container>

also support color state:

  <state name="color_state_text">
    <item flutter:color="@color/orange" flutter:state="hovered|focused"/>
    <item flutter:color="@color/darkGreen" flutter:state="dragged"/>
    <item flutter:color="@color/darkBlue"/>
  </state>

they were converted to dart's MaterialStateProperty<Color?> which some property needs.

complex property (todo)

more styles and themes were expected to custom just like android:

<resources>
  <theme name="titleText" parent="flutter:textTheme.headline3">
    <color>#f0f</color>
    <backgroundColor>#f0f</backgroundColor>
    <fontSize>14sp</fontSize>
    <fontStyle>italic</fontStyle>
  </theme>
</resources>
  <Text
    flutter:data="Flutter Xml Widget"
    flutter:style="@theme/titleText" />

databinding

If you are familiar with android development, you may use databinding to fill layout views with data by declaring variables in layout files. Actually it is very popular in front end world to describe views by template, especially in Vue. I borrowed its convention in xml_widget:

<Center>
  <Column
    flutter:mainAxisAlignment="center">
    <Text flutter:data="You have pushed the button this many times:"/>
    <Text flutter:data="{{something.some}}"
      flutter:style.color="@flutter:color/lightGreen"
      flutter:style="@theme/textTheme.headline4"/>
    <Text
      flutter:if="size < 0"
      flutter:data="size = {{size}}"
      flutter:style.color="@flutter:color/lightGreen"
      flutter:style="@theme/textTheme.headline4"/>
    <Text
      flutter:elseif="size == 0"
      flutter:data="size = {{size}}"
      flutter:style.color="@flutter:color/deepOrange"
      flutter:style="@theme/textTheme.headline4"/>
    <Text
      flutter:else=""
      flutter:data="size = {{size}}"
      flutter:style.color="@flutter:color/blueAccent"
      flutter:style="@theme/textTheme.headline4"/>
    <Flexible>
      <ListView>
        <Text
          flutter:data="header1"
          flutter:style.color="@flutter:color/orange"
          flutter:style="@theme/textTheme.headline2" />
        <Text
          flutter:data="header2"
          flutter:style.color="@flutter:color/blueAccent"
          flutter:style="@theme/textTheme.headline3" />

        <Text
          flutter:for="{{details}}"
          flutter:data="{{item.text}}"
          flutter:style.color="@flutter:color/deepOrangeAccent"
          flutter:style="@theme/textTheme.headline3" />
      </ListView>
    </Flexible>
  </Column>
</Center>

variable

variable data is declared within {{}} just like vue, actually whole statement in {{}} would be given to script engine to evaluate, so it is legal to write an expression in it, like {{size * 2 + 1}}. If using a variable not defined in script context, an error message created by script engine would be shown instead without crashing.

if statement

It is necessary to show different widget by if-else condition, in xml_widget this was also supported. Values of flutter:if and flutter:elseif would be given to script engine to evaluate. flutter:elseif and flutter:else matching with nearest flutter:if would be considered as one condition groups. So it is legal to write multiple conditions within same parent.

flutter:else have to be assigned with "" because of xml specification, different from Vue.

for statement

List view was most important view in client development. Node declared with flutter:for in ListView means item-widget would be built and item data template starts with item.. Other children would be consider header or footer.

A xml_widget app's structure is very simple:

  • a xml file representing view layout
  • a js file doing control logic
  • optional custom resource files

xml_widget depends on xml for xml file parsing and flutter_js for js engine!

supported widgets

  • Text
  • Column
  • Row
  • Wrap
  • Container
  • Ink
  • RaisedButton
  • FlatButton
  • OutlineButton
  • MaterialButton
  • ElevatedButton
  • TextButton
  • OutlinedButton
  • Padding
  • InkWell
  • Stack
  • Flex
  • Scaffold
  • FloatingActionButton
  • AppBar
  • Icon
  • Center
  • IntrinsicWidth
  • IntrinsicHeight
  • Image
  • Align
  • AspectRatio
  • FittedBox
  • Baseline
  • Positioned
  • SizedBox
  • Opacity
  • ListView
  • Flexible
  • Expanded

Libraries

build_item_widget
durian
model
model_widget
script_engine
xml_context
xml_resource