feat: 为Tabs增加lazy加载的功能

.changeset/nice-pans-confess.md

@@ -0,0 +1,5 @@
+---
+'@td-design/react-native-tabs': minor
+---
+
+feat: 为Tabs增加lazy功能

packages/react-native-tabs/src/SceneView.tsx

@@ -0,0 +1,51 @@
+import React, { useEffect } from 'react';
+import { View } from 'react-native';
+
+import { useSafeState } from '@td-design/rn-hooks';
+
+export default function SceneView({
+  lazy,
+  currentPage,
+  index,
+  children,
+}: {
+  lazy: boolean;
+  currentPage: number;
+  index: number;
+  children: (props: { loading: boolean }) => React.ReactNode;
+}) {
+  const [isLoading, setIsLoading] = useSafeState(lazy && Math.abs(currentPage - index) > 0);
+
+  if (isLoading && Math.abs(currentPage - index) <= 0 && lazy) {
+    setIsLoading(false);
+  }
+
+  useEffect(() => {
+    let timer: NodeJS.Timeout | undefined;
+
+    if (!lazy && isLoading) {
+      timer = setTimeout(() => {
+        setIsLoading(false);
+      }, 0);
+    }
+
+    return () => {
+      clearTimeout(timer);
+    };
+  }, [lazy, isLoading]);
+
+  const focused = currentPage === index;
+
+  return (
+    <View
+      accessibilityElementsHidden={!focused}
+      importantForAccessibility={focused ? 'auto' : 'no-hide-descendants'}
+      style={{
+        flex: 1,
+        overflow: 'hidden',
+      }}
+    >
+      {children({ loading: isLoading })}
+    </View>
+  );
+}

packages/react-native-tabs/src/index.md

@@ -197,6 +197,8 @@ return (
 | tabItemStyle        | `false` | 选项卡标签样式                             | `ViewStyle`         |           |
 | labelStyle          | `false` | 标签文字样式                               | `TextStyle`         |           |
 | indicatorStyle      | `false` | 指示器样式                                 | `ViewStyle`         |           |
+| lazy                | `false` | 是否启用懒加载模式                         | `boolean`           |           |
+| lazyPlaceholder     | `false` | 懒加载时的placeholder组件                  | `() => ReactNode`   |           |
 
 ```ts
 interface TabScene {

packages/react-native-tabs/src/index.tsx

@@ -1,9 +1,10 @@
-import React, { cloneElement } from 'react';
+import { ComponentType, createElement, memo } from 'react';
 import { Animated, StyleProp, TextStyle, ViewStyle } from 'react-native';
 import PagerView from 'react-native-pager-view';
 
 import { Box, helpers } from '@td-design/react-native';
 
+import SceneView from './SceneView';
 import ScrollBar from './ScrollBar';
 import TabBar from './TabBar';
 import usePagerView from './usePagerView';
@@ -13,11 +14,13 @@ const AnimatedPagerView = Animated.createAnimatedComponent<typeof PagerView>(Pag
 
 type Tab = {
   title: string;
-  component: JSX.Element;
+  component: ComponentType<any>;
 };
 
 export interface TabsProps {
   scenes: Tab[];
+  lazy?: boolean;
+  renderLazyPlaceholder?: () => JSX.Element;
   /** 默认当前是第几个tab */
   initialPage?: number;
   /** 当前是第几个tab */
@@ -42,6 +45,8 @@ export interface TabsProps {
 
 export default function Tabs({
   initialPage = 0,
+  lazy = false,
+  renderLazyPlaceholder,
   page,
   onChange,
   scenes = [],
@@ -103,8 +108,20 @@ export default function Tabs({
         onPageSelected={onPageSelected}
         onPageScrollStateChanged={onPageScrollStateChanged}
       >
-        {scenes.map(({ title, component }) => cloneElement(component, { key: title }))}
+        {scenes.map(({ component }, i) => (
+          <SceneView key={i} index={i} lazy={lazy} currentPage={currentPage}>
+            {({ loading }) => {
+              if (loading) return renderLazyPlaceholder?.();
+
+              return <SceneComponent {...{ component }} />;
+            }}
+          </SceneView>
+        ))}
       </AnimatedPagerView>
     </Box>
   );
 }
+
+const SceneComponent = memo(<T extends { component: ComponentType<any> }>({ component }: T) => {
+  return createElement(component);
+});

packages/react-native-tabs/src/types.tsx

@@ -0,0 +1,14 @@
+export type Route = {
+  key: string;
+  icon?: string;
+  title?: string;
+};
+
+export type Scene<T extends Route> = {
+  route: T;
+};
+
+export type NavigationState<T extends Route> = {
+  index: number;
+  routes: T[];
+};