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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。
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);
- }
-
-
- }

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。
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。
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'
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。
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