feat(Tabbar): add placeholder prop (#5979)

src/nav-bar/test/__snapshots__/index.spec.js.snap

@@ -1,7 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`placeholder prop 1`] = `
-<div class="van-nav-bar__placeholder" style="height: 0px;">
+<div class="van-nav-bar__placeholder" style="height: 50px;">
   <div class="van-nav-bar van-nav-bar--fixed van-hairline--bottom">
     <div class="van-nav-bar__left"></div>
     <div class="van-nav-bar__title van-ellipsis"></div>

src/nav-bar/test/index.spec.js

@@ -1,5 +1,5 @@
 import NavBar from '..';
-import { mount } from '../../../test';
+import { mount, mockGetBoundingClientRect } from '../../../test';
 
 test('render left & right slot', () => {
   const wrapper = mount(NavBar, {
@@ -23,6 +23,8 @@ test('render title slot', () => {
 });
 
 test('placeholder prop', () => {
+  const restore = mockGetBoundingClientRect({ height: 50 });
+
   const wrapper = mount(NavBar, {
     propsData: {
       fixed: true,
@@ -31,6 +33,8 @@ test('placeholder prop', () => {
   });
 
   expect(wrapper).toMatchSnapshot();
+
+  restore();
 });
 
 test('click-left event', () => {

src/tabbar/README.md

@@ -163,6 +163,7 @@ export default {
 | active-color | Color of active tab item | *string* | `#1989fa` |
 | inactive-color | Color of inactive tab item | *string* | `#7d7e80` |
 | route | Whether to enable route mode | *boolean* | `false` |
+| placeholder `v2.6.0` | Whether to generage a placeholder element when fixed | *boolean* | `false` |
 | safe-area-inset-bottom | Whether to enable bottom safe area adaptation | *boolean* | `false` |
 
 ### Tabbar Events

src/tabbar/README.zh-CN.md

@@ -170,6 +170,7 @@ export default {
 | active-color | 选中标签的颜色 | *string* | `#1989fa` |
 | inactive-color | 未选中标签的颜色 | *string* | `#7d7e80` |
 | route | 是否开启路由模式 | *boolean* | `false` |
+| placeholder `v2.6.0` | 固定在底部时，是否在标签位置生成一个等高的占位元素 | *boolean* | `false` |
 | safe-area-inset-bottom | 是否开启[底部安全区适配](#/zh-CN/quickstart#di-bu-an-quan-qu-gua-pei)，设置 fixed 时默认开启 | *boolean* | `false` |
 
 ### Tabbar Events

src/tabbar/index.js

@@ -10,6 +10,7 @@ export default createComponent({
   props: {
     route: Boolean,
     zIndex: [Number, String],
+    placeholder: Boolean,
     activeColor: String,
     inactiveColor: String,
     value: {
@@ -30,6 +31,12 @@ export default createComponent({
     },
   },
 
+  data() {
+    return {
+      height: null,
+    };
+  },
+
   computed: {
     fit() {
       if (this.safeAreaInsetBottom !== null) {
@@ -45,6 +52,12 @@ export default createComponent({
     children: 'setActiveItem',
   },
 
+  mounted() {
+    if (this.placeholder && this.fixed) {
+      this.height = this.$refs.tabbar.getBoundingClientRect().height;
+    }
+  },
+
   methods: {
     setActiveItem() {
       this.children.forEach((item, index) => {
@@ -58,22 +71,35 @@ export default createComponent({
         this.$emit('change', active);
       }
     },
+
+    genTabbar() {
+      return (
+        <div
+          ref="tabbar"
+          style={{ zIndex: this.zIndex }}
+          class={[
+            { [BORDER_TOP_BOTTOM]: this.border },
+            bem({
+              unfit: !this.fit,
+              fixed: this.fixed,
+            }),
+          ]}
+        >
+          {this.slots()}
+        </div>
+      );
+    },
   },
 
   render() {
-    return (
-      <div
-        style={{ zIndex: this.zIndex }}
-        class={[
-          { [BORDER_TOP_BOTTOM]: this.border },
-          bem({
-            unfit: !this.fit,
-            fixed: this.fixed,
-          }),
-        ]}
-      >
-        {this.slots()}
-      </div>
-    );
+    if (this.placeholder && this.fixed) {
+      return (
+        <div class={bem('placeholder')} style={{ height: `${this.height}px` }}>
+          {this.genTabbar()}
+        </div>
+      );
+    }
+
+    return this.genTabbar();
   },
 });

src/tabbar/test/__snapshots__/index.spec.js.snap

@@ -2,6 +2,12 @@
 
 exports[`disable border 1`] = `<div class="van-tabbar van-tabbar--fixed"></div>`;
 
+exports[`placeholder prop 1`] = `
+<div class="van-tabbar__placeholder" style="height: 50px;">
+  <div class="van-hairline--top-bottom van-tabbar van-tabbar--fixed"></div>
+</div>
+`;
+
 exports[`route mode 1`] = `
 <div class="van-hairline--top-bottom van-tabbar van-tabbar--fixed">
   <div class="van-tabbar-item van-tabbar-item--active">

src/tabbar/test/index.spec.js

@@ -1,5 +1,5 @@
 import VueRouter from 'vue-router';
-import { mount, later } from '../../../test';
+import { mount, later, mockGetBoundingClientRect } from '../../../test';
 import Vue from 'vue';
 import Tabbar from '..';
 
@@ -174,3 +174,18 @@ test('disable border', () => {
 
   expect(wrapper).toMatchSnapshot();
 });
+
+test('placeholder prop', () => {
+  const restore = mockGetBoundingClientRect({ height: 50 });
+
+  const wrapper = mount(Tabbar, {
+    propsData: {
+      fixed: true,
+      placeholder: true,
+    },
+  });
+
+  expect(wrapper).toMatchSnapshot();
+
+  restore();
+});