title: {
    bottom: 0,left: TITLE_OFFSET,right: TITLE_OFFSET,top: 0,position: 'absolute',alignItems: 'center',}

{Platform.OS === 'ios' &&
            title &&
            <Text
              onLayout={this._onTextLayout}
              style={[styles.title,{ color: tintColor }]}
              numberOfLines={1}
            >
              {backButtonTitle}
            </Text>}

componentDidMount () {
        /**
         * 将单击回调函数作为参数传递
         */
        this.props.navigation.setParams({
                switch: () => this.switchView()
        });
    }

/**
     * 切换视图
     */
    switchView() {
        alert('切换')
    }

static navigationOptions = ({navigation,screenProps}) => ({
        headerTitle: '企业服务',headerTitleStyle: CommonStyles.headerTitleStyle,headerRight: (
            <NavigatorItem icon={ Images.ic_navigator } onPress={ ()=> navigation.state.params.switch() }/>
        ),headerStyle: CommonStyles.headerStyle
    });

componentDidMount () {
        /**
         * 将单击回调函数作为参数传递
         */
        this.props.navigation.setParams({
                switch: () => this.switchView()
        });
    }

/**
     * 切换视图
     */
    switchView() {
        alert('切换')
    }

static navigationOptions = ({navigation,headerStyle: CommonStyles.headerStyle
    });

（4）结合BackHandler处理返回和点击返回键两次退出App效果

点击返回键两次退出App效果的需求屡见不鲜。相信很多人在react-navigation下实现该功能都遇到了很多问题，例如，其他界面不能返回。也就是手机本身返回事件在react-navigation之前拦截了。如何结合react-natigation实现呢？和大家分享两种实现方式：

（1）在注册StackNavigator的界面中，注册BackHandler：

componentWillMount(){
        BackHandler.addEventListener('hardwareBackPress',this._onBackAndroid );
    }


    componentUnWillMount(){
        BackHandler.addEventListener('hardwareBackPress',this._onBackAndroid);
    }

    _onBackAndroid=()=>{
        let now = new Date().getTime();
        if(now - lastBackPressed < 2500) {
            return false;
        }
        lastBackPressed = now;
        ToastAndroid.show('再点击一次退出应用',ToastAndroid.SHORT);
        return true;
    }

（2）监听react-navigation的Router

/**
 * 处理安卓返回键
 */
const defaultStateAction = AppNavigator.router.getStateForAction;
AppNavigator.router.getStateForAction = (action,state) => {
    if(state && action.type === NavigationActions.BACK && state.routes.length === 1) {
        if (lastBackPressed + 2000 < Date.now()) {
            ToastAndroid.show(Constant.hint_exit,ToastAndroid.SHORT);
            lastBackPressed = Date.now();
            const routes = [...state.routes];
            return {
                ...state,...state.routes,index: routes.length - 1,};
        }
    }
    return defaultStateAction(action,state);
};

（5）实现Android中界面跳转左右切换动画

react-navigation在Android中默认的界面切换动画是上下。如何实现左右切换呢？很简单的配置即可：

import CardStackStyleInterpolator from 'react-navigation/src/views/CardStackStyleInterpolator';

然后在StackNavigator的配置下添加如下代码：

transitionConfig:()=>({
            screenInterpolator: CardStackStyleInterpolator.forHorizontal,})

（6）解决快速点击多次跳转

当我们快速点击跳转时，会开启多个重复的界面，如何解决呢。其实在官方git中也有提示，解决这个问题需要修改react-navigation源码：

找到src文件夹中的addNavigationHelpers.js文件,替换为如下文本即可：

export default function<S: *>(navigation: NavigationProp<S,NavigationAction>) {
  // 添加点击判断
  let debounce = true;
  return {
      ...navigation,goBack: (key?: ?string): boolean =>
          navigation.dispatch(
              NavigationActions.back({
                  key: key === undefined ? navigation.state.key : key,}),),navigate: (routeName: string,params?: NavigationParams,action?: NavigationAction,): boolean => {
          if (debounce) {
              debounce = false;
              navigation.dispatch(
                  NavigationActions.navigate({
                      routeName,params,action,);
              setTimeout(
                  () => {
                      debounce = true;
                  },500,);
              return true;
          }
          return false;
      },/**
     * For updating current route params. For example the nav bar title and
     * buttons are based on the route params.
     * This means `setParams` can be used to update nav bar for example.
     */
    setParams: (params: NavigationParams): boolean =>
      navigation.dispatch(
        NavigationActions.setParams({
          params,key: navigation.state.key,};
}

（7）解决goBack，根据路由名称返回指定界面

react-navigation默认不支持根据路由名返回指定界面，官方只提供了根据Key来做goBack的指定返回。解决这个问题同样需要修改react-navigation源码，在Navigation.goBack条件下添加对路由名的支持。找到/node_modules/react-navigation/src/routers/StackRouter.js,全局搜索backRoute,将条件判断语句替换为如下代码：

if (action.type === NavigationActions.BACK) {
        const key = action.key;
        let backRouteIndex = null;
        if (key) {
          const backRoute = null;
          if(key.indexOf('id') >= 0) {
            backRoute = state.routes.find((route: *) => route.key === action.key);
          } else {
            backRoute = state.routes.find(route => route.routeName === action.key);
          }
          backRouteIndex = state.routes.indexOf(backRoute);
        }
        if (backRouteIndex == null) {
          return StateUtils.pop(state);
        }
        if (backRouteIndex > 0) {
          return {
            ...state,routes: state.routes.slice(0,backRouteIndex),index: backRouteIndex - 1,};
        }
      }

（8）自定义Tab

import React,{ Component } from 'react';
import {
    AppRegistry,Platform,StyleSheet,Text,View,TouchableOpacity,NativeModules,ImageBackground,DeviceEventEmitter
} from 'react-native';

export default class Tab extends Component {
    renderItem = (route,index) => {
        const {
            navigation,jumpToIndex,} = this.props;

        const focused = index === navigation.state.index;
        const color = focused ? this.props.activeTintColor : this.props.inactiveTintColor;
        let TabScene = {
            focused:focused,route:route,tintColor:color
        };

        if(index==1){
            return (<View style={[styles.tabItem,{backgroundColor:'transparent'}]}>
                    </View>
            );
        }

        return (
            <TouchableOpacity
                key={route.key}
                style={styles.tabItem}
                onPress={() => jumpToIndex(index)}
            >
                <View
                    style={styles.tabItem}>
                    {this.props.renderIcon(TabScene)}
                    <Text style={{ ...styles.tabText,marginTop:SCALE(10),color }}>{this.props.getLabel(TabScene)}</Text>
                </View>
            </TouchableOpacity>
        );
    };
    render(){
        const {navigation,jumpToIndex} = this.props;
        const {routes,} = navigation.state;
        const focused = 1 === navigation.state.index;
        const color = focused ? this.props.activeTintColor : this.props.inactiveTintColor;
        let TabScene = {
            focused:focused,route:routes[1],tintColor:color
        };
        return (
        <View style={{width:WIDTH}}>
            <View style={styles.tab}>
                {routes && routes.map((route,index) => this.renderItem(route,index))}
            </View>
            <TouchableOpacity
            key={"centerView"}
            style={[styles.tabItem,{position:'absolute',bottom:0,left:(WIDTH-SCALE(100))/2,right:WIDTH-SCALE(100),height:SCALE(120)}]}
            onPress={() => jumpToIndex(1)}
        >
            <View
                style={styles.tabItem}>
                {this.props.renderIcon(TabScene)}
                <Text style={{ ...styles.tabText,color }}>{this.props.getLabel(TabScene)}</Text>
            </View>
        </TouchableOpacity>
        </View>
        );
    }
}
const styles = {
    tab:{
        width:WIDTH,backgroundColor:'transparent',flexDirection:'row',justifyContent:'space-around',alignItems:'flex-end'
    },tabItem:{
        height:SCALE(80),width:SCALE(100),alignItems:'center',justifyContent:'center'
    },tabText:{
        marginTop:SCALE(13),fontSize:FONT(10),color:Color.C7b7b7b
    },tabTextChoose:{
        color:Color.f3474b
    },tabImage:{
        width:SCALE(42),height:SCALE(42),},}

componentDidMount () {
        /**
         * 将单击回调函数作为参数传递
         */
        this.props.navigation.setParams({
                switch: () => this.switchView()
        });
    }

/**
     * 切换视图
     */
    switchView() {
        alert('切换')
    }

static navigationOptions = ({navigation,headerStyle: CommonStyles.headerStyle
    });

（9）如何在屏幕控件之外的模块获取当前界面及navigation实例

很多情况下，我们都需要处理登录token失效的情况。例如：在当前设备登录后不退出，此时在另一台设备登录，导致第一个设备用户登录状态失效，此时在第一台设备操作网络请求时，需要提醒用户登录失效，跳转登录界面，并重新登录。

这种需求很常见，关于网络请求我们一般会封装为一个HttpUtil。然后在Component中去调用。此时如果需要处理登录失效的跳转逻辑，需要写在HttpUtil，那么在HttpUtil中就没办法获取navigation来做跳转，那么如何解决呢？下面提供一种方案，很实用：

定义一个Component的基类，包含当前显示的Component实例：screen，以及导航函数。

import React,{Component} from 'react';

export default class Base extends Component {
    static screen;

    constructor(props) {
        super(props);
        Base.screen = this; 
    }

    nav() {
        return this.props.navigation;
    }
}

在其他组件/模块中，我可以调用它来导航到不同的屏幕：

Base.screen.nav().navigate(...);

这样不管在哪个屏幕上，并且可以随时获取导航对象以在需要时重定向用户。

（10）react-navigation高级用法：实现自定义Tab切换效果。

react-navigation 库中提供了实现自定义Router切换的方式，需要用到的组件如下：

TabRouter,createNavigator,createNavigationContainer

1. TabRouter用来自定义路由栈

2.createNavigator用来创建导航组件

3.createNavigationContainer作为导航组件的容器组件

自定义Router切换的流程大致如下：

1. 创建StackNavigator

2. 创建TabRouter

3. 定义导航样式

4. 定义整体路由切换组件

5. 创建Navigator

来看核心代码：

// 界面组件
import FirstPage from './scene/FirstPage';
import SecondPage from './scene/SecondPage';
import ThirdPage from './scene/ThirdPage';
import DetailPage from './scene/DetailPage';

// 引入 react-navigation 核心组件
import { 
  TabRouter,StackNavigator,addNavigationHelpers,createNavigationContainer,} from 'react-navigation';

// 创建 3个 StackNavigator
const FirstScreen = StackNavigator(
  {
    First: {
      screen: FirstPage
    },Detail: {
      screen: DetailPage
    }
  }
);

const SecondScreen = StackNavigator(
  {
    Second: {
      screen: SecondPage
    }
  }
);

const ThirdScreen = StackNavigator(
  {
    Third: {
      screen: ThirdPage
    }
  }
);

// 定义 TabRouter

const FirstScene = ({ navigation }) => (
  <FirstScreen />
);
const SecondScene = ({ navigation }) => (
  <SecondScreen />
);
const ThirdScene = ({ navigation }) => (
  <ThirdScreen />
);

const CustomTabRouter = TabRouter(
  {
    First: {
      screen: FirstScene,path: 'firstScene'
    },Second: {
      screen: SecondScene,path: 'secondScene'
    },Third: {
      screen: ThirdScene,path: 'thirdScene'
    },{
    initialRouteName: 'First'
  }
);

// 定义TabBar
const CustomTabBar = ({ navigation,activeRouteName }) => {
  const { routes } = navigation.state;
  return (
    <View style={ styles.tabContainer }>
      <ScrollView>
          {
            routes.map((route,index)=>(
              <TouchableOpacity 
                key={ index } 
                onPress={() => navigation.navigate(route.routeName)}>
                <Text style={[ 
                  styles.tabbarText,activeRouteName === route.routeName ? styles.active : styles.inactive
                  ]}>
                  { route.routeName }
                </Text>
              </TouchableOpacity>
            ))
          }
      </ScrollView>
    </View>
  )
}

// 定义TabView 
const CustomTabView = ({ router,navigation }) => {
  const { routes,index } = navigation.state;
  const activeRouteName = routes[index].routeName;
  const ActiveScreen = router.getComponentForRouteName(activeRouteName);
  return(
    <View style={ styles.container }>
      <CustomTabBar 
        navigation={ navigation } 
        activeRouteName={ activeRouteName } />
      <ActiveScreen 
        navigation={
          addNavigationHelpers(
            {
              dispath: navigation.dispatch,state: routes[index]
            }
          )
        }
      />
    </View>
  )
}

// 创建Navigator
const CustomTabs = createNavigationContainer(
  createNavigator(CustomTabRouter)(CustomTabView)
)
export default CustomTabs;

// Style 样式
const styles = StyleSheet.create({
  tabContainer: {
    width: 86,zIndex: 888,flexDirection:'column',justifyContent:'center',backgroundColor: '#e7e7e7',borderRightWidth:1,borderColor: '#e0e0e0'
  },tabbarText: {
    fontSize: 18,fontWeight: 'bold',marginTop: 20,marginBottom: 20,color: 'black'
  },active: {
    color: 'red',inactive: {
    color: 'black',container: {
    flexDirection:'row',flex: 1,}
});

通过上述代码，我们就可以创建出类似于饿了么App中商品分类的模块切换效果。

（11）定义某个界面的切换动画效果

有时候产品会存在某个界面的切换动画和其他不同，那么如何实现呢？很简单，只需要在StackNavigator中配置参数下声明以下代码：

transitionConfig:()=>({
        screenInterpolator:
        (props)=> {
            const { scene } = props
            if (scene.route.routeName === 'VIPDetailPage') {
                return  CardStackStyleInterpolator.forFade
            } else {
                return CardStackStyleInterpolator.forHorizontal(props)
            }
       }
    })

效果图

自定义TabRouter：