【全网首发】鸿蒙开源三方组件--跨平台自适应布局yoga组件 精华

介绍

yoga是facebook打造的一个跨IOS、Android、Window平台在内的布局引擎，兼容Flexbox布局方式，让界面更加简单。
Yoga官网：https://facebook.github.io/yoga/

官网上描述的特性包括：

• 完全兼容Flexbox布局，遵循W3C的规范
• 支持java、C#、Objective-C、C四种语言
• 底层代码使用C语言编写，性能不是问题
• 支持流行框架如React Native

目前在已开源的鸿蒙组件（https://gitee.com/openharmony-tpc/yoga）的功能现状如下：

• native层和接口已经打通
• 支持自定义xml属性来控制布局（通过YogaLayout）
• 设置布局中不支持Image控件（onDrawCanvas暂不支持主动回调，所以yoga没办法扫描到它），请使用Text控件替代
• 不支持VirtualYogaLayout

如何使用

首先我们在MainAbility中定义界面路由

public class MainAbility extends Ability {
    @Override
    public void onStart(Intent intent) {
        super.onStart(intent);
        super.setMainRoute(MainAbilitySlice.class.getName());
        addActionRoute("action.dydrawnode.slice", DynamicsDrawNodeSlice.class.getName());
        addActionRoute("action.showrow.slice", ShowRowAbilitySlice.class.getName());
        addActionRoute("action.inflate.slice", BenchmarkInflateAbilitySlice.class.getName());
    }
}

然后我们来到MainAbilitySlice,其实就是做了一个向其他界面跳转的动作，并提前加载yoga的so库

public class MainAbilitySlice extends AbilitySlice {



    static {
        System.loadLibrary("yoga");
        System.loadLibrary("yogacore");
        System.loadLibrary("fb");
    }



    @Override
    public void onStart(Intent intent) {
        super.onStart(intent);
        setUIContent(ResourceTable.Layout_main_layout);

        Button btn0= (Button) findComponentById(ResourceTable.Id_btn_1);
        btn0.setClickedListener(component -> {
            Intent intent1 = new Intent();
            Operation operation = new Intent.OperationBuilder()
                    .withAction("action.dydrawnode.slice")
                    .build();
            intent1.setOperation(operation);
            startAbilityForResult(intent1, 1);
        });

        Button btn2= (Button) findComponentById(ResourceTable.Id_btn_2);
        btn2.setClickedListener(component -> {
            Intent intent1 = new Intent();
            Operation operation = new Intent.OperationBuilder()
                    .withAction("action.showrow.slice")
                    .build();
            intent1.setOperation(operation);
            startAbilityForResult(intent1, 1);
        });

        Button btn1= (Button) findComponentById(ResourceTable.Id_btn_3);
        btn1.setClickedListener(component -> {
            Intent intent1 = new Intent();
            Operation operation = new Intent.OperationBuilder()
                    .withAction("action.inflate.slice")
                    .build();
            intent1.setOperation(operation);
            startAbilityForResult(intent1, 1);
        });

    }

    @Override
    public void onActive() {
        super.onActive();
    }

    @Override
    public void onForeground(Intent intent) {
        super.onForeground(intent);
    }


}

第一个演示界面

这里yoga向我们展示了动态布局的能力，效果图如下：

实现的代码如下：

public class DynamicsDrawNodeSlice extends AbilitySlice {


    private static final int VIEW_WIDTH = 200;
    private static final int VIEW_HEIGHT = 200;

    private ArrayList<Component> mViewList = new ArrayList<>();
    private ArrayList<YogaNode> mYogaNodeList = new ArrayList<>();

    private int[][] colors = new int[][]{
            new int[]{0xff6200ea, 0xff651fff, 0xff7c4dff, 0xffb388ff},
            new int[]{0xffd50000, 0xffff1744, 0xffff5252, 0xffff8a80},
            new int[]{0xffc51162, 0xfff50057, 0xffff4081, 0xffff80ab},
            new int[]{0xffaa00ff, 0xffd500f9, 0xffe040fb, 0xffea80fc}
    };

    @Override
    protected void onStart(Intent intent) {
        super.onStart(intent);
        PositionLayout container = new PositionLayout(this);
        DisplayAttributes displayAttributes = DisplayManager.getInstance().getDefaultDisplay(this).get().getAttributes();
        float screenWidth = displayAttributes.width;
        float screenHeight = displayAttributes.height;
        YogaNode root = new YogaNodeJNIFinalizer();
        root.setWidth(screenWidth);
        root.setHeight(screenHeight);
        root.setFlexDirection(YogaFlexDirection.COLUMN);

        createRowNodeAndView(root, 0);
        createRowNodeAndView(root, 1);
        createRowNodeAndView(root, 2);
        createRowNodeAndView(root, 3);

        root.calculateLayout(screenWidth, screenHeight);

        for (int i = 0; i < mViewList.size(); i++) {
            Component component = mViewList.get(i);
            YogaNode yogaNode = mYogaNodeList.get(i);
            YogaNode yogaNodeOwner = yogaNode.getOwner();
            component.setTranslationX(yogaNodeOwner.getLayoutX() + yogaNodeOwner.getLayoutX());
            component.setTranslationY(yogaNodeOwner.getLayoutY() + yogaNodeOwner.getLayoutY());
            component.setLeft((int) (yogaNodeOwner.getLayoutX() + yogaNode.getLayoutX()));
            component.setTop((int) (yogaNodeOwner.getLayoutY() + yogaNode.getLayoutY()));
            container.addComponent(component);
        }

        super.setUIContent(container);
    }

    private void createRowNodeAndView(YogaNode root, int index) {
        YogaNode row = new YogaNodeJNIFinalizer();
        row.setHeight(VIEW_HEIGHT);
        row.setWidth(VIEW_WIDTH * 4);
        row.setFlexDirection(YogaFlexDirection.ROW);
        row.setMargin(YogaEdge.ALL, 20);

        for (int i = 0; i < 4; i++) {
            YogaNode yogaNode = new YogaNodeJNIFinalizer();
            yogaNode.setWidth(VIEW_WIDTH);
            yogaNode.setHeight(VIEW_HEIGHT);
            Component component = createView(colors[index][i]);
            row.addChildAt(yogaNode, i);
            mYogaNodeList.add(yogaNode);
            mViewList.add(component);
        }

        root.addChildAt(row, index);
    }

    private Component createView(int color) {
        Component view = new Component(this);
        ShapeElement background = new ShapeElement();
        background.setRgbColor(convertColor(color));
        view.setBackground(background);
        ComponentContainer.LayoutConfig layoutConfig = new AdaptiveBoxLayout.LayoutConfig(VIEW_WIDTH, VIEW_HEIGHT);
        view.setLayoutConfig(layoutConfig);
        return view;
    }

    /**
     *  转换颜色
     * @param color
     * @return RgbColor
     */
    public RgbColor convertColor(int color) {
        int colorInt = color;
        int red = (colorInt & 0xff0000) >> 16;
        int green = (colorInt & 0x00ff00) >> 8;
        int blue = (colorInt & 0x0000ff);
        return new RgbColor(red, green, blue);
    }
}

代码中定义了一个root根布局，宽高为屏幕的宽高，接着定义了四个行布局，并向每个行布局里添加4个子布局，最重要的是在调用root.calculateLayout(screenWidth, screenHeight)后，便将每个子布局的位置给确定了下来，然后根据获取到的每个布局的参数，给每个Component设置位置。该演示只是借助yoga组件来确定每个Component位置，真正使渲染生效的还是基于鸿蒙的原生控件。

第二个演示界面

接下来展示如何使用yoga组件在xml里通过填写属性来控制item位置的能力，效果图如下：

代码如下：

<?xml version="1.0" encoding="utf-8" ?>
<com.facebook.yoga.openharmony.YogaLayout
       xmlns:ohos="http://schemas.huawei.com/res/ohos"
       xmlns:yoga="http://schemas.huawei.com/apk/res-auto"
       ohos:height="match_parent"
       ohos:width="match_parent"
>

   <com.facebook.yoga.openharmony.YogaLayout
           ohos:height="60vp"
           ohos:width="match_content"
           yoga:yg_alignItems="center"
           yoga:yg_flexDirection="row"
           yoga:yg_marginHorizontal="15"
           yoga:yg_marginStart="15"
           yoga:yg_marginTop="50"
           ohos:background_element="$graphic:item_element"
   >


       <Text
               ohos:height="50vp"
               ohos:width="50vp"
               ohos:background_element="$media:icon"
               yoga:yg_flex="0"
               yoga:yg_marginStart="15"
       />


       <Text
               ohos:height="50vp"
               ohos:width="220vp"
               ohos:text="Hello.  I am Yoga!"
               ohos:text_color="#000000"
               yoga:yg_flex="1"
               yoga:yg_marginStart="15"
               ohos:text_size="20fp"
       />
   </com.facebook.yoga.openharmony.YogaLayout>

   <com.facebook.yoga.openharmony.YogaLayout
           ohos:background_element="$graphic:item_element"
           ohos:height="60vp"
           ohos:width="match_content"
           yoga:yg_alignItems="center"
           yoga:yg_flexDirection="row"
           yoga:yg_marginHorizontal="15"
           yoga:yg_marginTop="20"
           yoga:yg_marginStart="15"
   >


       <Text
               ohos:height="50vp"
               ohos:width="50vp"
               ohos:background_element="$media:icon"
               yoga:yg_flex="0"
               yoga:yg_marginStart="15"
       />

       <Text
               ohos:height="50vp"
               ohos:width="250vp"
               ohos:text="I am a layout engine!"
               ohos:text_color="#000000"
               yoga:yg_flex="1"
               yoga:yg_marginStart="15"
               ohos:text_size="20fp"
       />
   </com.facebook.yoga.openharmony.YogaLayout>

   <com.facebook.yoga.openharmony.YogaLayout
           ohos:background_element="$graphic:item_element"
           ohos:height="60vp"
           ohos:width="match_content"
           yoga:yg_alignItems="center"
           yoga:yg_flexDirection="row"
           yoga:yg_marginHorizontal="15"
           yoga:yg_marginTop="20"
   >

       <Text
               ohos:height="50vp"
               ohos:width="50vp"
               ohos:background_element="$media:icon"
               yoga:yg_flex="0"
               yoga:yg_marginStart="15"
       />

       <Text
               ohos:height="50vp"
               ohos:width="250vp"
               ohos:text="I run natively."
               ohos:text_color="#000000"
               yoga:yg_flex="1"
               yoga:yg_marginStart="15"
               ohos:text_size="20fp"
       />
   </com.facebook.yoga.openharmony.YogaLayout>

   <com.facebook.yoga.openharmony.YogaLayout
           ohos:background_element="$graphic:item_element"
           ohos:height="60vp"
           ohos:width="match_content"
           yoga:yg_alignItems="center"
           yoga:yg_flexDirection="row"
           yoga:yg_marginHorizontal="15"
           yoga:yg_marginTop="20"
   >

       <Text
               ohos:height="50vp"
               ohos:width="50vp"
               ohos:background_element="$media:icon"
               yoga:yg_flex="0"
       />

       <Text
               ohos:height="50vp"
               ohos:width="200vp"
               ohos:text="So I\'m fast."
               ohos:text_color="#000000"
               yoga:yg_flex="1"
               yoga:yg_marginStart="15"
               ohos:text_size="20fp"
       />
   </com.facebook.yoga.openharmony.YogaLayout>

   <com.facebook.yoga.openharmony.YogaLayout
           ohos:background_element="$graphic:item_element"
           ohos:height="60vp"
           ohos:width="match_content"
           yoga:yg_alignItems="center"
           yoga:yg_flexDirection="row"
           yoga:yg_marginHorizontal="15"
           yoga:yg_marginTop="20"
   >

       <Text
               ohos:height="50vp"
               ohos:width="50vp"
               ohos:background_element="$media:icon"
               yoga:yg_flex="0"
       />

       <Text
               ohos:height="50vp"
               ohos:width="200vp"
               ohos:text="Who are you?"
               ohos:text_color="#000000"
               yoga:yg_flex="1"
               yoga:yg_marginStart="15"
               ohos:text_size="20fp"
       />
   </com.facebook.yoga.openharmony.YogaLayout>

</com.facebook.yoga.openharmony.YogaLayout>

这里YogaLayout其实可以看成FlexBox（详情请参考附录：FlexBox科普），可以通过参数调节子布局位置，我们可以使用YogaLayout上的yoga:yg_alignItems="center"属性使得item居中显示，并通过yoga:yg_flexDirection="row"属性使得之item横向排列。子item也可以通过设置yoga:yg_flex="1"来调整自己的权重。更多属性的使用大家也可以下载项目亲自体验。

集成方式

自行编译工程entity、yoga、yoga_layout、fb生成libyoga.so、libfb.so、libyogacore.so
将其添加到要集成的libs文件夹内，在entity的gradle内添加如下代码。

方式一：
通过library生成har包，添加har包到libs文件夹内。
在entry的gradle内添加如下代码：

implementation fileTree(dir:'libs', include:['*.jar','*.har'])

方式二：

allprojects{
	repositories{
		mavenCentral()
	}
}
implementation 'io.openharmony.tpc.thirdlib:yoga-layout:1.0.0'
implementation 'io.openharmony.tpc.thirdlib:yoga-yoga:1.0.0'
implementation 'io.openharmony.tpc.thirdlib:yoga-fb:1.0.0'

附录1：FlexBox科普

布局的传统解决方案，基于盒状模型，依赖display属性，position属性，float属性。它对于那些特殊布局非常不方便，比如，垂直居中就不容易实现。2009年，W3C提出了一种新的方案：flex。可以简便、完整、响应式地实现各种界面布局。目前，该方案已经得到了所有浏览器的支持。采用Flex布局的元素，称为Flex容器（flex container），简称“容器”。它的所有子元素置动成为容器成员，称为Flex项目（flex item），简称“项目”。

容器默认存在两根轴：水平的主轴（main axis）和垂直的交叉轴（cross axis）。主轴的开始位置（与边框的交叉点）叫main start，结束位置叫main end；交叉轴的开始位置叫cross start，结束位置叫cross end。项目默认沿主轴排列。单个项目占据的主轴空间叫main size，占据的交叉轴空间叫cross size。

附录2：相关资料

• 项目地址：https://gitee.com/openharmony-tpc/yoga
• IDE官方下载地址：https://developer.harmonyos.com/cn/develop/deveco-studio
• 阮一峰的flex布局教程：http://www.ruanyifeng.com/blog/2015/07/flex-grammar.html