xml_layout

XML layout for flutter. Layout your UI via xml at runtime. and support extending any customer widget. Here is a online preview.

Getting Started

write xml layout file like:

xml

<Text mainAxisAlignment="center">
    <for count="6">
        <Text>$item, You have pushed the button this many times:</Text>
    </for>
    <Text id="text-id">
        <attr:style>
            <TextStyle color="red"/>
        </attr:style>
        $counter
    </Text>
</Column>

dart

XMLLayout(
    temp: snapshot.data,
    objects: {
        "counter": _counter
    },
)

In this case

$counter for passing argument to the layout.

id attribute for selecting the widget or state.

XMLLayoutState state = ...;
// find the key of the Text 
GlobalKey key = state.find('text-id');

Registers

• register
  • description: Register a constructor. It could convert a xml element to target object.

/**
 * Register a constructor
 * 
 * xml:
 * <MyClass width="10" height="10" />
 * 
 */
XMLLayout.register('MyClass', (node, key) {
    return MyClass(
        key: key,
        child: node.child<Widget>(),
        width: node.s<double>("width"),
        height: node.s<double>("height"),
    );
});

• registerEnum
  • description: A shortcat to register a enum class. It could convert a attribute to the enum.

/**
* Register a enum type
* 
* xml:
* <Text textAlign="center">str</Text>
*/
XMLLayout.registerEnum(TextAlign.values);

• registerInline(Type type, String name, bool field, InlineItemConstructor constructor)
  • description: Register a constructor which could convert a attribute to target type.
  • arguments:
    • field this constructor is for a static field or a constructor.

/**
 * <Text fontWeight="w200">str</Text>
 */
XmlLayout.registerInline(FontWeight, "w200", true, (node, method) {
  return FontWeight.w200;
});

/**
 * <Text textHeightBehavior="fromEncoded(20)">str</Text>
 */
XmlLayout.registerInline(TextHeightBehavior, "fromEncoded", false,
      (node, method) {
  return TextHeightBehavior.fromEncoded(int.tryParse(method[0]));
});

node.s<T>("name"), node.attribute<T>("name") convert subnode to target type

node.t<T>(), node.convert<T>() convert this node to target type

node.v<T>("value"), node.value<T>("value") convert text to target type

Widget Builder

<ListView.separated itemCount="$itemCount">
    <attr:itemBuilder>
        <Function returnType="Widget">
            <!-- get arguments of function via args -->
            <SetArgument return="index" argument="${args[1]}"/>
            <Call function="$getItem" return="itemData">
                <!-- pass argument to getItem function -->
                <Argument value="$index"/>
            </Call>
            <!-- The last element of Function tag would be the final result -->
            <Text>${itemData.title}</Text>
        </Function>
    </attr:itemBuilder>
</ListView.separated>

Script

<Function>
    <Script>
        set("index", ${args[1]})
        set("itemData", getItem($index))
    </Script>
    <!-- same as -->
    <SetArgument return="index" argument="${args[1]}"/>
    <Call function="$getItem" return="itemData">
        <Argument value="$index"/>
    </Call>
    <!-- end(same as) -->

    <Text>${itemData.title}</Text>
</Function>

Method

Method could be registerd via XmlLayout.registerInlineMethod, and can be used in a Xml attribute or Script tag.

Default methods:

• isEmpty(a) => a.isEmpty()
• isNotEmpty(a) => a.isNotEmpty()
• equal(a, b, ...) => a == b ...
• net(a, b) => a != b
• mod(a, b) => a % b
• div(a, b) => a / b
• set(name, a) => envname = a
• not(a) => !a
• lt(a, b) => a < b
• nlt(a, b) => a >= b
• gt(a, b) => a > b
• ngt(a, b) => a <= b
• plus(a, b, ...) => a + b ...
• minus(a, b, ...) => a - b ...
• multiply(a, b, ...) => a * b ...
• divide(a, b, ...) => a / b ...

Control Flow

A util to control the rendering logic. like:

<for count="$counter">
    <Text>$item, You have pushed the button this many times:</Text>
    <if candidate="equal(1, mod($item, 2))">
        <Text>Test text</Text>
    </if>
</for>

• if tag is a if control flow.
  • attributes:
    • candidate a Boolean value, if true the children would be rendered, otherwise not be rendered.
• else tag is a else control flow, could be placed after if or another else tag.
  • attributes:
    • candidate same as if tag.
• for tag is a loop control flow.
  • attributes:
    • array a List value, iterates over array elements, each element for children one time.
    • count a Integer value, iterates children the value times. It is mutually exclusive with the array attribute.
    • item a String value, the name of each element, default is item.
    • index a String value, the name of the index of element, default is index.

Builder

You can write a script to generate the constructor code. In the example test.dart is the builder script.

Builder options:

• entry_name
  • default: types
  • type: List<Type>
  • description: types in this list which will be processed.
• collections_name
  • default: collections
  • type: List<Collection>
  • description: Collection type is used to process the collection class, such as: Colors and Icons.

ps: Colors and Icons is preprocessed just import it via:

import 'package:xml_layout/types/colors.dart' as colors;
import 'package:xml_layout/types/icons.dart' as icons;

// ...

colors.register();
icons.register();

• coverts_name
  • default: converts
  • type: Map<String, String>
  • description: Every import uri will be test by the key value pair in this variable. if a import source uri is start with the key then it will be convert to the value.
• imports_name
  • default: imports
  • type: List<String>
  • description: Extension import uris which will be write to the generated code.

Example

lib/test.dart

import 'package:flutter/material.dart';

const List<Type> types = [
  Text,
];

build.yaml

targets:
  $default:
    builders:
      xml_layout:
        generate_for:
          - lib/test.dart

Create the files above, then just run flutter pub run build_runner build. And you will get the generated code in lib/test.xml_layout.dart.